Rewrite AV1 intra prediction for SIMD

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DcFillPredictor.cs

@@ -1,69 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block with the sample-domain midpoint when neither top nor left neighbors are available.
-/// </summary>
-internal readonly struct Av1DcFillPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of samples written to each destination row.
-    /// </summary>
-    private readonly uint blockWidth;
-
-    /// <summary>
-    /// The number of destination rows.
-    /// </summary>
-    private readonly uint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcFillPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1DcFillPredictor(Size blockSize)
-    {
-        this.blockWidth = (uint)blockSize.Width;
-        this.blockHeight = (uint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcFillPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1DcFillPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (uint)transformSize.GetWidth();
-        this.blockHeight = (uint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block with the 8-bit midpoint value.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The unused top-neighbor buffer required by the common predictor signature.</param>
-    /// <param name="left">The unused left-neighbor buffer required by the common predictor signature.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1DcFillPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        // With no reference edge, AV1 uses the midpoint of the unsigned 8-bit sample domain as the DC predictor.
-        const byte expectedDc = 0x80;
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte destinationRef = ref destination[0];
-        for (uint r = 0; r < this.blockHeight; r++)
-        {
-            Unsafe.InitBlock(ref destinationRef, expectedDc, this.blockWidth);
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DcIntraPredictor.cs

@@ -0,0 +1,245 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+/// <summary>
+/// Reconstructs AV1 DC intra-prediction blocks from the available neighboring samples.
+/// </summary>
+internal static class Av1DcIntraPredictor
+{
+    /// <summary>
+    /// Predicts an 8-bit DC block.
+    /// </summary>
+    /// <param name="hasLeft">Whether the prepared left reference is available.</param>
+    /// <param name="hasAbove">Whether the prepared top reference is available.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    public static void Predict(bool hasLeft, bool hasAbove, Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height)
+    {
+        int count = (hasAbove ? width : 0) + (hasLeft ? height : 0);
+        int sum = (hasAbove ? Sum(above[..width]) : 0) + (hasLeft ? Sum(left[..height]) : 0);
+
+        // Section 7.11.2.2 defines the unsigned midpoint when no reference is available. Otherwise adding half
+        // the reference count implements the specified rounded mean before extending it across the whole block.
+        byte prediction = count == 0 ? (byte)128 : (byte)((sum + (count >> 1)) / count);
+        for (int row = 0; row < height; row++)
+        {
+            destination.Slice(row * destinationStride, width).Fill(prediction);
+        }
+    }
+
+    /// <summary>
+    /// Predicts a high-bit-depth DC block.
+    /// </summary>
+    /// <param name="hasLeft">Whether the prepared left reference is available.</param>
+    /// <param name="hasAbove">Whether the prepared top reference is available.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    /// <param name="bitDepth">The reconstructed sample precision.</param>
+    public static void Predict(bool hasLeft, bool hasAbove, Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height, int bitDepth)
+    {
+        int count = (hasAbove ? width : 0) + (hasLeft ? height : 0);
+        int sum = (hasAbove ? Sum(above[..width]) : 0) + (hasLeft ? Sum(left[..height]) : 0);
+        short prediction = count == 0 ? (short)(1 << (bitDepth - 1)) : (short)((sum + (count >> 1)) / count);
+        for (int row = 0; row < height; row++)
+        {
+            destination.Slice(row * destinationStride, width).Fill(prediction);
+        }
+    }
+
+    /// <summary>
+    /// Predicts an 8-bit DC block without hardware intrinsics.
+    /// </summary>
+    /// <param name="hasLeft">Whether the prepared left reference is available.</param>
+    /// <param name="hasAbove">Whether the prepared top reference is available.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    public static void PredictScalar(bool hasLeft, bool hasAbove, Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height)
+    {
+        int count = (hasAbove ? width : 0) + (hasLeft ? height : 0);
+        int sum = (hasAbove ? SumScalar(above[..width]) : 0) + (hasLeft ? SumScalar(left[..height]) : 0);
+        byte prediction = count == 0 ? (byte)128 : (byte)((sum + (count >> 1)) / count);
+        for (int row = 0; row < height; row++)
+        {
+            ref byte destinationRow = ref destination[row * destinationStride];
+            for (int column = 0; column < width; column++)
+            {
+                Unsafe.Add(ref destinationRow, column) = prediction;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Predicts a high-bit-depth DC block without hardware intrinsics.
+    /// </summary>
+    /// <param name="hasLeft">Whether the prepared left reference is available.</param>
+    /// <param name="hasAbove">Whether the prepared top reference is available.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    /// <param name="bitDepth">The reconstructed sample precision.</param>
+    public static void PredictScalar(bool hasLeft, bool hasAbove, Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height, int bitDepth)
+    {
+        int count = (hasAbove ? width : 0) + (hasLeft ? height : 0);
+        int sum = (hasAbove ? SumScalar(above[..width]) : 0) + (hasLeft ? SumScalar(left[..height]) : 0);
+        short prediction = count == 0 ? (short)(1 << (bitDepth - 1)) : (short)((sum + (count >> 1)) / count);
+        for (int row = 0; row < height; row++)
+        {
+            ref short destinationRow = ref destination[row * destinationStride];
+            for (int column = 0; column < width; column++)
+            {
+                Unsafe.Add(ref destinationRow, column) = prediction;
+            }
+        }
+    }
+
+    /// <summary>
+    /// Sums 8-bit neighboring samples using the widest available SIMD width.
+    /// </summary>
+    /// <param name="samples">The samples to sum.</param>
+    /// <returns>The exact sum.</returns>
+    private static int Sum(ReadOnlySpan<byte> samples)
+    {
+        ref byte samplesBase = ref MemoryMarshal.GetReference(samples);
+        int sum = 0;
+        int index = 0;
+
+        if (Vector512.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = samples.Length - Vector512<byte>.Count;
+            for (; index <= oneVectorFromEnd; index += Vector512<byte>.Count)
+            {
+                (Vector512<ushort> low, Vector512<ushort> high) = Vector512.Widen(Vector512.LoadUnsafe(ref samplesBase, (nuint)index));
+                sum += Vector512.Sum(low) + Vector512.Sum(high);
+            }
+        }
+
+        if (Vector256.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = samples.Length - Vector256<byte>.Count;
+            for (; index <= oneVectorFromEnd; index += Vector256<byte>.Count)
+            {
+                (Vector256<ushort> low, Vector256<ushort> high) = Vector256.Widen(Vector256.LoadUnsafe(ref samplesBase, (nuint)index));
+                sum += Vector256.Sum(low) + Vector256.Sum(high);
+            }
+        }
+
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = samples.Length - Vector128<byte>.Count;
+            for (; index <= oneVectorFromEnd; index += Vector128<byte>.Count)
+            {
+                (Vector128<ushort> low, Vector128<ushort> high) = Vector128.Widen(Vector128.LoadUnsafe(ref samplesBase, (nuint)index));
+                sum += Vector128.Sum(low) + Vector128.Sum(high);
+            }
+        }
+
+        for (; index < samples.Length; index++)
+        {
+            sum += Unsafe.Add(ref samplesBase, index);
+        }
+
+        return sum;
+    }
+
+    /// <summary>
+    /// Sums high-bit-depth neighboring samples using the widest available SIMD width.
+    /// </summary>
+    /// <param name="samples">The samples to sum.</param>
+    /// <returns>The exact sum.</returns>
+    private static int Sum(ReadOnlySpan<short> samples)
+    {
+        ref short samplesBase = ref MemoryMarshal.GetReference(samples);
+        int sum = 0;
+        int index = 0;
+
+        if (Vector512.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = samples.Length - Vector512<short>.Count;
+            for (; index <= oneVectorFromEnd; index += Vector512<short>.Count)
+            {
+                (Vector512<int> low, Vector512<int> high) = Vector512.Widen(Vector512.LoadUnsafe(ref samplesBase, (nuint)index));
+                sum += Vector512.Sum(low) + Vector512.Sum(high);
+            }
+        }
+
+        if (Vector256.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = samples.Length - Vector256<short>.Count;
+            for (; index <= oneVectorFromEnd; index += Vector256<short>.Count)
+            {
+                (Vector256<int> low, Vector256<int> high) = Vector256.Widen(Vector256.LoadUnsafe(ref samplesBase, (nuint)index));
+                sum += Vector256.Sum(low) + Vector256.Sum(high);
+            }
+        }
+
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = samples.Length - Vector128<short>.Count;
+            for (; index <= oneVectorFromEnd; index += Vector128<short>.Count)
+            {
+                (Vector128<int> low, Vector128<int> high) = Vector128.Widen(Vector128.LoadUnsafe(ref samplesBase, (nuint)index));
+                sum += Vector128.Sum(low) + Vector128.Sum(high);
+            }
+        }
+
+        for (; index < samples.Length; index++)
+        {
+            sum += Unsafe.Add(ref samplesBase, index);
+        }
+
+        return sum;
+    }
+
+    /// <summary>
+    /// Sums 8-bit neighboring samples without hardware intrinsics.
+    /// </summary>
+    /// <param name="samples">The samples to sum.</param>
+    /// <returns>The exact sum.</returns>
+    private static int SumScalar(ReadOnlySpan<byte> samples)
+    {
+        int sum = 0;
+        foreach (byte sample in samples)
+        {
+            sum += sample;
+        }
+
+        return sum;
+    }
+
+    /// <summary>
+    /// Sums high-bit-depth neighboring samples without hardware intrinsics.
+    /// </summary>
+    /// <param name="samples">The samples to sum.</param>
+    /// <returns>The exact sum.</returns>
+    private static int SumScalar(ReadOnlySpan<short> samples)
+    {
+        int sum = 0;
+        foreach (short sample in samples)
+        {
+            sum += sample;
+        }
+
+        return sum;
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DcLeftPredictor.cs

@@ -1,77 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block from the rounded average of its available left neighboring samples.
-/// </summary>
-internal readonly struct Av1DcLeftPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of samples written to each destination row.
-    /// </summary>
-    private readonly uint blockWidth;
-
-    /// <summary>
-    /// The number of left samples averaged and destination rows written.
-    /// </summary>
-    private readonly uint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcLeftPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1DcLeftPredictor(Size blockSize)
-    {
-        this.blockWidth = (uint)blockSize.Width;
-        this.blockHeight = (uint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcLeftPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1DcLeftPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (uint)transformSize.GetWidth();
-        this.blockHeight = (uint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block from its left neighboring samples.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The unused top-neighbor buffer required by the common predictor signature.</param>
-    /// <param name="left">The left neighboring samples.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1DcLeftPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        int sum = 0;
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte leftRef = ref left[0];
-        ref byte destinationRef = ref destination[0];
-        for (uint i = 0; i < this.blockHeight; i++)
-        {
-            sum += Unsafe.Add(ref leftRef, i);
-        }
-
-        // Adding half the sample count implements the normative nearest-integer DC average before division.
-        byte expectedDc = (byte)((sum + (this.blockHeight >> 1)) / this.blockHeight);
-        for (uint r = 0; r < this.blockHeight; r++)
-        {
-            Unsafe.InitBlock(ref destinationRef, expectedDc, this.blockWidth);
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DcPredictor.cs

@@ -1,86 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block from the rounded average of its top and left neighboring samples.
-/// </summary>
-internal readonly struct Av1DcPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of top samples averaged and samples written to each destination row.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The number of left samples averaged and destination rows written.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1DcPredictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1DcPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block from its top and left neighboring samples.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top neighboring samples.</param>
-    /// <param name="left">The left neighboring samples.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1DcPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        int sum = 0;
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte leftRef = ref left[0];
-        ref byte aboveRef = ref above[0];
-        ref byte destinationRef = ref destination[0];
-        uint count = (uint)(this.blockWidth + this.blockHeight);
-        uint width = (uint)this.blockWidth;
-        for (nuint i = 0; i < this.blockWidth; i++)
-        {
-            sum += Unsafe.Add(ref aboveRef, i);
-        }
-
-        for (nuint i = 0; i < this.blockHeight; i++)
-        {
-            sum += Unsafe.Add(ref leftRef, i);
-        }
-
-        // Adding half the combined edge count implements the normative nearest-integer DC average before division.
-        byte expectedDc = (byte)((sum + (count >> 1)) / count);
-        for (nuint r = 0; r < this.blockHeight; r++)
-        {
-            Unsafe.InitBlock(ref destinationRef, expectedDc, width);
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DcTopPredictor.cs

@@ -1,77 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block from the rounded average of its available top neighboring samples.
-/// </summary>
-internal readonly struct Av1DcTopPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of top samples averaged and samples written to each destination row.
-    /// </summary>
-    private readonly uint blockWidth;
-
-    /// <summary>
-    /// The number of destination rows.
-    /// </summary>
-    private readonly uint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcTopPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1DcTopPredictor(Size blockSize)
-    {
-        this.blockWidth = (uint)blockSize.Width;
-        this.blockHeight = (uint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DcTopPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1DcTopPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (uint)transformSize.GetWidth();
-        this.blockHeight = (uint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block from its top neighboring samples.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top neighboring samples.</param>
-    /// <param name="left">The unused left-neighbor buffer required by the common predictor signature.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1DcTopPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        int sum = 0;
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte aboveRef = ref above[0];
-        ref byte destinationRef = ref destination[0];
-        for (uint i = 0; i < this.blockWidth; i++)
-        {
-            sum += Unsafe.Add(ref aboveRef, i);
-        }
-
-        // Adding half the sample count implements the normative nearest-integer DC average before division.
-        byte expectedDc = (byte)((sum + (this.blockWidth >> 1)) / this.blockWidth);
-        for (uint r = 0; r < this.blockHeight; r++)
-        {
-            Unsafe.InitBlock(ref destinationRef, expectedDc, this.blockWidth);
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DirectionalIntraPredictor.Simd.cs

@@ -0,0 +1,619 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+/// <content>
+/// Provides the SIMD projection kernels for AV1 directional intra prediction.
+/// </content>
+internal static partial class Av1DirectionalIntraPredictor
+{
+    /// <summary>
+    /// Gets the indices of even bytes in one upsampled reference vector.
+    /// </summary>
+    private static Vector128<byte> EvenByteIndices => Vector128.Create((byte)0, 2, 4, 6, 8, 10, 12, 14, 0, 2, 4, 6, 8, 10, 12, 14);
+
+    /// <summary>
+    /// Gets the indices of odd bytes in one upsampled reference vector.
+    /// </summary>
+    private static Vector128<byte> OddByteIndices => Vector128.Create((byte)1, 3, 5, 7, 9, 11, 13, 15, 1, 3, 5, 7, 9, 11, 13, 15);
+
+    /// <summary>
+    /// Gets the indices of even high-bit-depth samples in one upsampled reference vector.
+    /// </summary>
+    private static Vector128<short> EvenShortIndices => Vector128.Create((short)0, 2, 4, 6, 0, 2, 4, 6);
+
+    /// <summary>
+    /// Gets the indices of odd high-bit-depth samples in one upsampled reference vector.
+    /// </summary>
+    private static Vector128<short> OddShortIndices => Vector128.Create((short)1, 3, 5, 7, 1, 3, 5, 7);
+
+    /// <summary>
+    /// Predicts one 8-bit zone 1 block using contiguous SIMD projection rows.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="upsample">Whether the reference contains half-sample positions.</param>
+    /// <param name="derivative">The Q8 projection derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone1(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, bool upsample, int derivative, int width, int height)
+    {
+        int upsampleShift = upsample ? 1 : 0;
+        int maximumBasis = (width + height - 1) << upsampleShift;
+        int fractionBits = 6 - upsampleShift;
+        int projection = derivative;
+
+        for (int row = 0; row < height; row++, projection += derivative)
+        {
+            int basis = projection >> fractionBits;
+            int weight = ((projection << upsampleShift) & 0x3F) >> 1;
+            InterpolateRow(destination.Slice(row * destinationStride, width), above, basis, weight, upsample, maximumBasis);
+        }
+    }
+
+    /// <summary>
+    /// Predicts one high-bit-depth zone 1 block using contiguous SIMD projection rows.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="upsample">Whether the reference contains half-sample positions.</param>
+    /// <param name="derivative">The Q8 projection derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone1(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, bool upsample, int derivative, int width, int height)
+    {
+        int upsampleShift = upsample ? 1 : 0;
+        int maximumBasis = (width + height - 1) << upsampleShift;
+        int fractionBits = 6 - upsampleShift;
+        int projection = derivative;
+
+        for (int row = 0; row < height; row++, projection += derivative)
+        {
+            int basis = projection >> fractionBits;
+            int weight = ((projection << upsampleShift) & 0x3F) >> 1;
+            InterpolateRow(destination.Slice(row * destinationStride, width), above, basis, weight, upsample, maximumBasis);
+        }
+    }
+
+    /// <summary>
+    /// Predicts one 8-bit zone 2 block using vectorized left gathers and contiguous top projection rows.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="upsampleAbove">Whether the top reference contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left reference contains half-sample positions.</param>
+    /// <param name="dx">The horizontal Q8 derivative.</param>
+    /// <param name="dy">The vertical Q8 derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone2(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, bool upsampleAbove, bool upsampleLeft, int dx, int dy, int width, int height)
+    {
+        int aboveShift = upsampleAbove ? 1 : 0;
+        int minimumTopBasis = -(1 << aboveShift);
+        int topFractionBits = 6 - aboveShift;
+        int topBasisIncrement = 1 << aboveShift;
+        int topProjection = -dx;
+
+        for (int row = 0; row < height; row++, topProjection -= dx)
+        {
+            int topBasis = topProjection >> topFractionBits;
+            int leftCount = 0;
+            while (leftCount < width && topBasis < minimumTopBasis)
+            {
+                leftCount++;
+                topBasis += topBasisIncrement;
+            }
+
+            Span<byte> destinationRow = destination.Slice(row * destinationStride, width);
+            int leftProjection = (row << 6) - dy;
+            InterpolateLeft(destinationRow[..leftCount], left, leftProjection, dy, upsampleLeft);
+
+            if (leftCount < width)
+            {
+                int topWeight = ((topProjection << aboveShift) & 0x3F) >> 1;
+                InterpolateRow(destinationRow[leftCount..], above, topBasis, topWeight, upsampleAbove, int.MaxValue);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Predicts one high-bit-depth zone 2 block using vectorized left gathers and contiguous top projection rows.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="upsampleAbove">Whether the top reference contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left reference contains half-sample positions.</param>
+    /// <param name="dx">The horizontal Q8 derivative.</param>
+    /// <param name="dy">The vertical Q8 derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone2(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, bool upsampleAbove, bool upsampleLeft, int dx, int dy, int width, int height)
+    {
+        int aboveShift = upsampleAbove ? 1 : 0;
+        int minimumTopBasis = -(1 << aboveShift);
+        int topFractionBits = 6 - aboveShift;
+        int topBasisIncrement = 1 << aboveShift;
+        int topProjection = -dx;
+
+        for (int row = 0; row < height; row++, topProjection -= dx)
+        {
+            int topBasis = topProjection >> topFractionBits;
+            int leftCount = 0;
+            while (leftCount < width && topBasis < minimumTopBasis)
+            {
+                leftCount++;
+                topBasis += topBasisIncrement;
+            }
+
+            Span<short> destinationRow = destination.Slice(row * destinationStride, width);
+            int leftProjection = (row << 6) - dy;
+            InterpolateLeft(destinationRow[..leftCount], left, leftProjection, dy, upsampleLeft);
+
+            if (leftCount < width)
+            {
+                int topWeight = ((topProjection << aboveShift) & 0x3F) >> 1;
+                InterpolateRow(destinationRow[leftCount..], above, topBasis, topWeight, upsampleAbove, int.MaxValue);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Interpolates one 8-bit projection row.
+    /// </summary>
+    /// <param name="destination">The destination row.</param>
+    /// <param name="reference">The projected reference samples.</param>
+    /// <param name="basis">The first integral reference coordinate.</param>
+    /// <param name="weight">The right-sample interpolation weight.</param>
+    /// <param name="upsample">Whether consecutive output samples advance two reference positions.</param>
+    /// <param name="maximumBasis">The final extended reference coordinate, or <see cref="int.MaxValue"/> when the row cannot reach it.</param>
+    private static void InterpolateRow(Span<byte> destination, ReadOnlySpan<byte> reference, int basis, int weight, bool upsample, int maximumBasis)
+    {
+        ref byte destinationBase = ref MemoryMarshal.GetReference(destination);
+        ref byte referenceBase = ref MemoryMarshal.GetReference(reference);
+        int basisIncrement = upsample ? 2 : 1;
+        int validCount = maximumBasis == int.MaxValue || basis >= maximumBasis
+            ? maximumBasis == int.MaxValue ? destination.Length : 0
+            : Math.Min(destination.Length, ((maximumBasis - 1 - basis) / basisIncrement) + 1);
+        int index = 0;
+
+        if (!upsample)
+        {
+            if (Vector512.IsHardwareAccelerated)
+            {
+                int oneVectorFromEnd = validCount - Vector512<byte>.Count;
+                for (; index <= oneVectorFromEnd; index += Vector512<byte>.Count)
+                {
+                    Vector512<byte> left = Vector512.LoadUnsafe(ref referenceBase, (nuint)(basis + index));
+                    Vector512<byte> right = Vector512.LoadUnsafe(ref referenceBase, (nuint)(basis + index + 1));
+                    Interpolate(left, right, weight).StoreUnsafe(ref destinationBase, (nuint)index);
+                }
+            }
+
+            if (Vector256.IsHardwareAccelerated)
+            {
+                int oneVectorFromEnd = validCount - Vector256<byte>.Count;
+                for (; index <= oneVectorFromEnd; index += Vector256<byte>.Count)
+                {
+                    Vector256<byte> left = Vector256.LoadUnsafe(ref referenceBase, (nuint)(basis + index));
+                    Vector256<byte> right = Vector256.LoadUnsafe(ref referenceBase, (nuint)(basis + index + 1));
+                    Interpolate(left, right, weight).StoreUnsafe(ref destinationBase, (nuint)index);
+                }
+            }
+
+            if (Vector128.IsHardwareAccelerated)
+            {
+                int oneVectorFromEnd = validCount - Vector128<byte>.Count;
+                for (; index <= oneVectorFromEnd; index += Vector128<byte>.Count)
+                {
+                    Vector128<byte> left = Vector128.LoadUnsafe(ref referenceBase, (nuint)(basis + index));
+                    Vector128<byte> right = Vector128.LoadUnsafe(ref referenceBase, (nuint)(basis + index + 1));
+                    Interpolate(left, right, weight).StoreUnsafe(ref destinationBase, (nuint)index);
+                }
+            }
+        }
+        else if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = validCount - 8;
+            for (; index <= oneVectorFromEnd; index += 8)
+            {
+                Vector128<byte> source = Vector128.LoadUnsafe(ref referenceBase, (nuint)(basis + (index * 2)));
+
+                // ShuffleNative maps to byte-table lookup on AdvSimd and PSHUFB on x86. Eight output samples are
+                // gathered from sixteen half-sample positions without scalar lane construction.
+                Vector128<byte> left = Vector128.ShuffleNative(source, EvenByteIndices);
+                Vector128<byte> right = Vector128.ShuffleNative(source, OddByteIndices);
+                Vector128<byte> prediction = Interpolate(left, right, weight);
+                Unsafe.As<byte, ulong>(ref Unsafe.Add(ref destinationBase, index)) = prediction.AsUInt64().GetElement(0);
+            }
+        }
+
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = validCount - 4;
+            for (; index <= oneVectorFromEnd; index += 4)
+            {
+                int source = basis + (index * basisIncrement);
+                Vector128<int> left = Vector128.Create(
+                    (int)Unsafe.Add(ref referenceBase, source),
+                    Unsafe.Add(ref referenceBase, source + basisIncrement),
+                    Unsafe.Add(ref referenceBase, source + (2 * basisIncrement)),
+                    Unsafe.Add(ref referenceBase, source + (3 * basisIncrement)));
+
+                Vector128<int> right = Vector128.Create(
+                    (int)Unsafe.Add(ref referenceBase, source + 1),
+                    Unsafe.Add(ref referenceBase, source + basisIncrement + 1),
+                    Unsafe.Add(ref referenceBase, source + (2 * basisIncrement) + 1),
+                    Unsafe.Add(ref referenceBase, source + (3 * basisIncrement) + 1));
+
+                StoreFourBytes(Interpolate(left, right, Vector128.Create(weight)), ref Unsafe.Add(ref destinationBase, index));
+            }
+        }
+
+        for (; index < validCount; index++)
+        {
+            int source = basis + (index * basisIncrement);
+            Unsafe.Add(ref destinationBase, index) = (byte)(((Unsafe.Add(ref referenceBase, source) * (32 - weight)) + (Unsafe.Add(ref referenceBase, source + 1) * weight) + 16) >> 5);
+        }
+
+        if (validCount < destination.Length)
+        {
+            destination[validCount..].Fill(Unsafe.Add(ref referenceBase, maximumBasis));
+        }
+    }
+
+    /// <summary>
+    /// Interpolates one high-bit-depth projection row.
+    /// </summary>
+    /// <param name="destination">The destination row.</param>
+    /// <param name="reference">The projected reference samples.</param>
+    /// <param name="basis">The first integral reference coordinate.</param>
+    /// <param name="weight">The right-sample interpolation weight.</param>
+    /// <param name="upsample">Whether consecutive output samples advance two reference positions.</param>
+    /// <param name="maximumBasis">The final extended reference coordinate, or <see cref="int.MaxValue"/> when the row cannot reach it.</param>
+    private static void InterpolateRow(Span<short> destination, ReadOnlySpan<short> reference, int basis, int weight, bool upsample, int maximumBasis)
+    {
+        ref short destinationBase = ref MemoryMarshal.GetReference(destination);
+        ref short referenceBase = ref MemoryMarshal.GetReference(reference);
+        int basisIncrement = upsample ? 2 : 1;
+        int validCount = maximumBasis == int.MaxValue || basis >= maximumBasis
+            ? maximumBasis == int.MaxValue ? destination.Length : 0
+            : Math.Min(destination.Length, ((maximumBasis - 1 - basis) / basisIncrement) + 1);
+        int index = 0;
+
+        if (!upsample)
+        {
+            if (Vector512.IsHardwareAccelerated)
+            {
+                int oneVectorFromEnd = validCount - Vector512<short>.Count;
+                for (; index <= oneVectorFromEnd; index += Vector512<short>.Count)
+                {
+                    Vector512<short> left = Vector512.LoadUnsafe(ref referenceBase, (nuint)(basis + index));
+                    Vector512<short> right = Vector512.LoadUnsafe(ref referenceBase, (nuint)(basis + index + 1));
+                    Interpolate(left, right, weight).StoreUnsafe(ref destinationBase, (nuint)index);
+                }
+            }
+
+            if (Vector256.IsHardwareAccelerated)
+            {
+                int oneVectorFromEnd = validCount - Vector256<short>.Count;
+                for (; index <= oneVectorFromEnd; index += Vector256<short>.Count)
+                {
+                    Vector256<short> left = Vector256.LoadUnsafe(ref referenceBase, (nuint)(basis + index));
+                    Vector256<short> right = Vector256.LoadUnsafe(ref referenceBase, (nuint)(basis + index + 1));
+                    Interpolate(left, right, weight).StoreUnsafe(ref destinationBase, (nuint)index);
+                }
+            }
+
+            if (Vector128.IsHardwareAccelerated)
+            {
+                int oneVectorFromEnd = validCount - Vector128<short>.Count;
+                for (; index <= oneVectorFromEnd; index += Vector128<short>.Count)
+                {
+                    Vector128<short> left = Vector128.LoadUnsafe(ref referenceBase, (nuint)(basis + index));
+                    Vector128<short> right = Vector128.LoadUnsafe(ref referenceBase, (nuint)(basis + index + 1));
+                    Interpolate(left, right, weight).StoreUnsafe(ref destinationBase, (nuint)index);
+                }
+            }
+        }
+        else if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = validCount - 4;
+            for (; index <= oneVectorFromEnd; index += 4)
+            {
+                Vector128<short> source = Vector128.LoadUnsafe(ref referenceBase, (nuint)(basis + (index * 2)));
+                Vector128<short> left = Vector128.ShuffleNative(source, EvenShortIndices);
+                Vector128<short> right = Vector128.ShuffleNative(source, OddShortIndices);
+                Vector128<short> prediction = Interpolate(left, right, weight);
+                Unsafe.As<short, ulong>(ref Unsafe.Add(ref destinationBase, index)) = prediction.AsUInt64().GetElement(0);
+            }
+        }
+
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = validCount - 4;
+            for (; index <= oneVectorFromEnd; index += 4)
+            {
+                int source = basis + (index * basisIncrement);
+                Vector128<int> left = Vector128.Create(
+                    (int)Unsafe.Add(ref referenceBase, source),
+                    Unsafe.Add(ref referenceBase, source + basisIncrement),
+                    Unsafe.Add(ref referenceBase, source + (2 * basisIncrement)),
+                    Unsafe.Add(ref referenceBase, source + (3 * basisIncrement)));
+
+                Vector128<int> right = Vector128.Create(
+                    (int)Unsafe.Add(ref referenceBase, source + 1),
+                    Unsafe.Add(ref referenceBase, source + basisIncrement + 1),
+                    Unsafe.Add(ref referenceBase, source + (2 * basisIncrement) + 1),
+                    Unsafe.Add(ref referenceBase, source + (3 * basisIncrement) + 1));
+
+                StoreFourShorts(Interpolate(left, right, Vector128.Create(weight)), ref Unsafe.Add(ref destinationBase, index));
+            }
+        }
+
+        for (; index < validCount; index++)
+        {
+            int source = basis + (index * basisIncrement);
+            Unsafe.Add(ref destinationBase, index) = (short)(((Unsafe.Add(ref referenceBase, source) * (32 - weight)) + (Unsafe.Add(ref referenceBase, source + 1) * weight) + 16) >> 5);
+        }
+
+        if (validCount < destination.Length)
+        {
+            destination[validCount..].Fill(Unsafe.Add(ref referenceBase, maximumBasis));
+        }
+    }
+
+    /// <summary>
+    /// Interpolates the left-edge prefix of one 8-bit zone 2 row.
+    /// </summary>
+    /// <param name="destination">The destination prefix.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="projection">The first Q6 left projection.</param>
+    /// <param name="derivative">The Q8 derivative subtracted between columns.</param>
+    /// <param name="upsample">Whether the left reference contains half-sample positions.</param>
+    private static void InterpolateLeft(Span<byte> destination, ReadOnlySpan<byte> left, int projection, int derivative, bool upsample)
+    {
+        ref byte destinationBase = ref MemoryMarshal.GetReference(destination);
+        ref byte leftBase = ref MemoryMarshal.GetReference(left);
+        int upsampleShift = upsample ? 1 : 0;
+        int fractionBits = 6 - upsampleShift;
+        int index = 0;
+
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = destination.Length - 4;
+            for (; index <= oneVectorFromEnd; index += 4)
+            {
+                int projection0 = projection - (index * derivative);
+                int projection1 = projection0 - derivative;
+                int projection2 = projection1 - derivative;
+                int projection3 = projection2 - derivative;
+                int basis0 = projection0 >> fractionBits;
+                int basis1 = projection1 >> fractionBits;
+                int basis2 = projection2 >> fractionBits;
+                int basis3 = projection3 >> fractionBits;
+                Vector128<int> source0 = Vector128.Create((int)Unsafe.Add(ref leftBase, basis0), Unsafe.Add(ref leftBase, basis1), Unsafe.Add(ref leftBase, basis2), Unsafe.Add(ref leftBase, basis3));
+                Vector128<int> source1 = Vector128.Create((int)Unsafe.Add(ref leftBase, basis0 + 1), Unsafe.Add(ref leftBase, basis1 + 1), Unsafe.Add(ref leftBase, basis2 + 1), Unsafe.Add(ref leftBase, basis3 + 1));
+                Vector128<int> weights = Vector128.Create(
+                    ((projection0 << upsampleShift) & 0x3F) >> 1,
+                    ((projection1 << upsampleShift) & 0x3F) >> 1,
+                    ((projection2 << upsampleShift) & 0x3F) >> 1,
+                    ((projection3 << upsampleShift) & 0x3F) >> 1);
+
+                StoreFourBytes(Interpolate(source0, source1, weights), ref Unsafe.Add(ref destinationBase, index));
+            }
+        }
+
+        for (; index < destination.Length; index++)
+        {
+            int currentProjection = projection - (index * derivative);
+            int basis = currentProjection >> fractionBits;
+            int weight = ((currentProjection << upsampleShift) & 0x3F) >> 1;
+            Unsafe.Add(ref destinationBase, index) = (byte)(((Unsafe.Add(ref leftBase, basis) * (32 - weight)) + (Unsafe.Add(ref leftBase, basis + 1) * weight) + 16) >> 5);
+        }
+    }
+
+    /// <summary>
+    /// Interpolates the left-edge prefix of one high-bit-depth zone 2 row.
+    /// </summary>
+    /// <param name="destination">The destination prefix.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="projection">The first Q6 left projection.</param>
+    /// <param name="derivative">The Q8 derivative subtracted between columns.</param>
+    /// <param name="upsample">Whether the left reference contains half-sample positions.</param>
+    private static void InterpolateLeft(Span<short> destination, ReadOnlySpan<short> left, int projection, int derivative, bool upsample)
+    {
+        ref short destinationBase = ref MemoryMarshal.GetReference(destination);
+        ref short leftBase = ref MemoryMarshal.GetReference(left);
+        int upsampleShift = upsample ? 1 : 0;
+        int fractionBits = 6 - upsampleShift;
+        int index = 0;
+
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int oneVectorFromEnd = destination.Length - 4;
+            for (; index <= oneVectorFromEnd; index += 4)
+            {
+                int projection0 = projection - (index * derivative);
+                int projection1 = projection0 - derivative;
+                int projection2 = projection1 - derivative;
+                int projection3 = projection2 - derivative;
+                int basis0 = projection0 >> fractionBits;
+                int basis1 = projection1 >> fractionBits;
+                int basis2 = projection2 >> fractionBits;
+                int basis3 = projection3 >> fractionBits;
+                Vector128<int> source0 = Vector128.Create((int)Unsafe.Add(ref leftBase, basis0), Unsafe.Add(ref leftBase, basis1), Unsafe.Add(ref leftBase, basis2), Unsafe.Add(ref leftBase, basis3));
+                Vector128<int> source1 = Vector128.Create((int)Unsafe.Add(ref leftBase, basis0 + 1), Unsafe.Add(ref leftBase, basis1 + 1), Unsafe.Add(ref leftBase, basis2 + 1), Unsafe.Add(ref leftBase, basis3 + 1));
+                Vector128<int> weights = Vector128.Create(
+                    ((projection0 << upsampleShift) & 0x3F) >> 1,
+                    ((projection1 << upsampleShift) & 0x3F) >> 1,
+                    ((projection2 << upsampleShift) & 0x3F) >> 1,
+                    ((projection3 << upsampleShift) & 0x3F) >> 1);
+
+                StoreFourShorts(Interpolate(source0, source1, weights), ref Unsafe.Add(ref destinationBase, index));
+            }
+        }
+
+        for (; index < destination.Length; index++)
+        {
+            int currentProjection = projection - (index * derivative);
+            int basis = currentProjection >> fractionBits;
+            int weight = ((currentProjection << upsampleShift) & 0x3F) >> 1;
+            Unsafe.Add(ref destinationBase, index) = (short)(((Unsafe.Add(ref leftBase, basis) * (32 - weight)) + (Unsafe.Add(ref leftBase, basis + 1) * weight) + 16) >> 5);
+        }
+    }
+
+    /// <summary>
+    /// Interpolates sixty-four pairs of 8-bit references.
+    /// </summary>
+    /// <param name="left">The left interpolation samples.</param>
+    /// <param name="right">The right interpolation samples.</param>
+    /// <param name="weight">The right-sample weight.</param>
+    /// <returns>The rounded interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector512<byte> Interpolate(Vector512<byte> left, Vector512<byte> right, int weight)
+    {
+        (Vector512<ushort> leftLow, Vector512<ushort> leftHigh) = Vector512.Widen(left);
+        (Vector512<ushort> rightLow, Vector512<ushort> rightHigh) = Vector512.Widen(right);
+        Vector512<ushort> rounding = Vector512.Create((ushort)16);
+        Vector512<ushort> low = ((leftLow * (ushort)(32 - weight)) + (rightLow * (ushort)weight) + rounding) >> 5;
+        Vector512<ushort> high = ((leftHigh * (ushort)(32 - weight)) + (rightHigh * (ushort)weight) + rounding) >> 5;
+        return Vector512.Narrow(low, high);
+    }
+
+    /// <summary>
+    /// Interpolates thirty-two pairs of 8-bit references.
+    /// </summary>
+    /// <param name="left">The left interpolation samples.</param>
+    /// <param name="right">The right interpolation samples.</param>
+    /// <param name="weight">The right-sample weight.</param>
+    /// <returns>The rounded interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector256<byte> Interpolate(Vector256<byte> left, Vector256<byte> right, int weight)
+    {
+        (Vector256<ushort> leftLow, Vector256<ushort> leftHigh) = Vector256.Widen(left);
+        (Vector256<ushort> rightLow, Vector256<ushort> rightHigh) = Vector256.Widen(right);
+        Vector256<ushort> rounding = Vector256.Create((ushort)16);
+        Vector256<ushort> low = ((leftLow * (ushort)(32 - weight)) + (rightLow * (ushort)weight) + rounding) >> 5;
+        Vector256<ushort> high = ((leftHigh * (ushort)(32 - weight)) + (rightHigh * (ushort)weight) + rounding) >> 5;
+        return Vector256.Narrow(low, high);
+    }
+
+    /// <summary>
+    /// Interpolates sixteen pairs of 8-bit references.
+    /// </summary>
+    /// <param name="left">The left interpolation samples.</param>
+    /// <param name="right">The right interpolation samples.</param>
+    /// <param name="weight">The right-sample weight.</param>
+    /// <returns>The rounded interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<byte> Interpolate(Vector128<byte> left, Vector128<byte> right, int weight)
+    {
+        (Vector128<ushort> leftLow, Vector128<ushort> leftHigh) = Vector128.Widen(left);
+        (Vector128<ushort> rightLow, Vector128<ushort> rightHigh) = Vector128.Widen(right);
+        Vector128<ushort> rounding = Vector128.Create((ushort)16);
+        Vector128<ushort> low = ((leftLow * (ushort)(32 - weight)) + (rightLow * (ushort)weight) + rounding) >> 5;
+        Vector128<ushort> high = ((leftHigh * (ushort)(32 - weight)) + (rightHigh * (ushort)weight) + rounding) >> 5;
+        return Vector128.Narrow(low, high);
+    }
+
+    /// <summary>
+    /// Interpolates thirty-two pairs of high-bit-depth references.
+    /// </summary>
+    /// <param name="left">The left interpolation samples.</param>
+    /// <param name="right">The right interpolation samples.</param>
+    /// <param name="weight">The right-sample weight.</param>
+    /// <returns>The rounded interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector512<short> Interpolate(Vector512<short> left, Vector512<short> right, int weight)
+    {
+        (Vector512<int> leftLow, Vector512<int> leftHigh) = Vector512.Widen(left);
+        (Vector512<int> rightLow, Vector512<int> rightHigh) = Vector512.Widen(right);
+        Vector512<int> rounding = Vector512.Create(16);
+        Vector512<int> low = ((leftLow * (32 - weight)) + (rightLow * weight) + rounding) >> 5;
+        Vector512<int> high = ((leftHigh * (32 - weight)) + (rightHigh * weight) + rounding) >> 5;
+        return Vector512.Narrow(low, high);
+    }
+
+    /// <summary>
+    /// Interpolates sixteen pairs of high-bit-depth references.
+    /// </summary>
+    /// <param name="left">The left interpolation samples.</param>
+    /// <param name="right">The right interpolation samples.</param>
+    /// <param name="weight">The right-sample weight.</param>
+    /// <returns>The rounded interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector256<short> Interpolate(Vector256<short> left, Vector256<short> right, int weight)
+    {
+        (Vector256<int> leftLow, Vector256<int> leftHigh) = Vector256.Widen(left);
+        (Vector256<int> rightLow, Vector256<int> rightHigh) = Vector256.Widen(right);
+        Vector256<int> rounding = Vector256.Create(16);
+        Vector256<int> low = ((leftLow * (32 - weight)) + (rightLow * weight) + rounding) >> 5;
+        Vector256<int> high = ((leftHigh * (32 - weight)) + (rightHigh * weight) + rounding) >> 5;
+        return Vector256.Narrow(low, high);
+    }
+
+    /// <summary>
+    /// Interpolates eight pairs of high-bit-depth references.
+    /// </summary>
+    /// <param name="left">The left interpolation samples.</param>
+    /// <param name="right">The right interpolation samples.</param>
+    /// <param name="weight">The right-sample weight.</param>
+    /// <returns>The rounded interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<short> Interpolate(Vector128<short> left, Vector128<short> right, int weight)
+    {
+        (Vector128<int> leftLow, Vector128<int> leftHigh) = Vector128.Widen(left);
+        (Vector128<int> rightLow, Vector128<int> rightHigh) = Vector128.Widen(right);
+        Vector128<int> rounding = Vector128.Create(16);
+        Vector128<int> low = ((leftLow * (32 - weight)) + (rightLow * weight) + rounding) >> 5;
+        Vector128<int> high = ((leftHigh * (32 - weight)) + (rightHigh * weight) + rounding) >> 5;
+        return Vector128.Narrow(low, high);
+    }
+
+    /// <summary>
+    /// Interpolates four widened reference pairs with independent weights.
+    /// </summary>
+    /// <param name="left">The left interpolation samples.</param>
+    /// <param name="right">The right interpolation samples.</param>
+    /// <param name="weights">The right-sample weights.</param>
+    /// <returns>The rounded interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<int> Interpolate(Vector128<int> left, Vector128<int> right, Vector128<int> weights)
+        => ((left * (Vector128.Create(32) - weights)) + (right * weights) + Vector128.Create(16)) >> 5;
+
+    /// <summary>
+    /// Stores four widened predictions as packed 8-bit samples.
+    /// </summary>
+    /// <param name="prediction">The widened predictions.</param>
+    /// <param name="destination">The first destination sample.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void StoreFourBytes(Vector128<int> prediction, ref byte destination)
+    {
+        Vector128<ushort> narrowed16 = Vector128.Narrow(prediction.AsUInt32(), Vector128<uint>.Zero);
+        Vector128<byte> narrowed8 = Vector128.Narrow(narrowed16, Vector128<ushort>.Zero);
+        Unsafe.As<byte, uint>(ref destination) = narrowed8.AsUInt32().GetElement(0);
+    }
+
+    /// <summary>
+    /// Stores four widened predictions as packed high-bit-depth samples.
+    /// </summary>
+    /// <param name="prediction">The widened predictions.</param>
+    /// <param name="destination">The first destination sample.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void StoreFourShorts(Vector128<int> prediction, ref short destination)
+    {
+        Vector128<short> narrowed = Vector128.Narrow(prediction, Vector128<int>.Zero);
+        Unsafe.As<short, ulong>(ref destination) = narrowed.AsUInt64().GetElement(0);
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DirectionalIntraPredictor.Transpose.cs

@@ -0,0 +1,313 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Intrinsics;
+using SixLabors.ImageSharp.Common.Helpers;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+/// <content>
+/// Provides SIMD block transposition for zone 3 directional prediction.
+/// </content>
+internal static partial class Av1DirectionalIntraPredictor
+{
+    /// <summary>
+    /// Transposes a contiguous 8-bit prediction block into the reconstructed destination.
+    /// </summary>
+    /// <param name="source">The contiguous source block.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="sourceWidth">The source row width.</param>
+    /// <param name="sourceHeight">The number of source rows.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    private static void Transpose(ReadOnlySpan<byte> source, Span<byte> destination, int sourceWidth, int sourceHeight, int destinationStride)
+    {
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int tileSize = sourceWidth >= 8 && sourceHeight >= 8 ? 8 : 4;
+            for (int y = 0; y < sourceHeight; y += tileSize)
+            {
+                for (int x = 0; x < sourceWidth; x += tileSize)
+                {
+                    if (tileSize == 8)
+                    {
+                        Transpose8x8(source, destination, sourceWidth, destinationStride, x, y);
+                    }
+                    else
+                    {
+                        Transpose4x4(source, destination, sourceWidth, destinationStride, x, y);
+                    }
+                }
+            }
+
+            return;
+        }
+
+        for (int y = 0; y < sourceHeight; y++)
+        {
+            for (int x = 0; x < sourceWidth; x++)
+            {
+                destination[(x * destinationStride) + y] = source[(y * sourceWidth) + x];
+            }
+        }
+    }
+
+    /// <summary>
+    /// Transposes a contiguous high-bit-depth prediction block into the reconstructed destination.
+    /// </summary>
+    /// <param name="source">The contiguous source block.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="sourceWidth">The source row width.</param>
+    /// <param name="sourceHeight">The number of source rows.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    private static void Transpose(ReadOnlySpan<short> source, Span<short> destination, int sourceWidth, int sourceHeight, int destinationStride)
+    {
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int tileSize = sourceWidth >= 8 && sourceHeight >= 8 ? 8 : 4;
+            for (int y = 0; y < sourceHeight; y += tileSize)
+            {
+                for (int x = 0; x < sourceWidth; x += tileSize)
+                {
+                    if (tileSize == 8)
+                    {
+                        Transpose8x8(source, destination, sourceWidth, destinationStride, x, y);
+                    }
+                    else
+                    {
+                        Transpose4x4(source, destination, sourceWidth, destinationStride, x, y);
+                    }
+                }
+            }
+
+            return;
+        }
+
+        for (int y = 0; y < sourceHeight; y++)
+        {
+            for (int x = 0; x < sourceWidth; x++)
+            {
+                destination[(x * destinationStride) + y] = source[(y * sourceWidth) + x];
+            }
+        }
+    }
+
+    /// <summary>
+    /// Transposes one eight-by-eight tile of 8-bit prediction samples.
+    /// </summary>
+    /// <param name="source">The contiguous source block.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="sourceStride">The source row stride.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="x">The tile X coordinate.</param>
+    /// <param name="y">The tile Y coordinate.</param>
+    private static void Transpose8x8(ReadOnlySpan<byte> source, Span<byte> destination, int sourceStride, int destinationStride, int x, int y)
+    {
+        ref byte sourceBase = ref MemoryMarshal.GetReference(source);
+        ref byte destinationBase = ref MemoryMarshal.GetReference(destination);
+        Vector128<byte> row0 = LoadEightBytes(ref sourceBase, ((y + 0) * sourceStride) + x);
+        Vector128<byte> row1 = LoadEightBytes(ref sourceBase, ((y + 1) * sourceStride) + x);
+        Vector128<byte> row2 = LoadEightBytes(ref sourceBase, ((y + 2) * sourceStride) + x);
+        Vector128<byte> row3 = LoadEightBytes(ref sourceBase, ((y + 3) * sourceStride) + x);
+        Vector128<byte> row4 = LoadEightBytes(ref sourceBase, ((y + 4) * sourceStride) + x);
+        Vector128<byte> row5 = LoadEightBytes(ref sourceBase, ((y + 5) * sourceStride) + x);
+        Vector128<byte> row6 = LoadEightBytes(ref sourceBase, ((y + 6) * sourceStride) + x);
+        Vector128<byte> row7 = LoadEightBytes(ref sourceBase, ((y + 7) * sourceStride) + x);
+
+        // Three unpack stages exchange one, two, then four byte coordinates. Each final vector contains two
+        // complete source columns, which are written as two contiguous eight-byte destination rows.
+        Vector128<byte> pair0 = Vector128_.UnpackLow(row0, row1);
+        Vector128<byte> pair2 = Vector128_.UnpackLow(row2, row3);
+        Vector128<byte> pair4 = Vector128_.UnpackLow(row4, row5);
+        Vector128<byte> pair6 = Vector128_.UnpackLow(row6, row7);
+        Vector128<short> quad0 = Vector128_.UnpackLow(pair0.AsInt16(), pair2.AsInt16());
+        Vector128<short> quad1 = Vector128_.UnpackHigh(pair0.AsInt16(), pair2.AsInt16());
+        Vector128<short> quad4 = Vector128_.UnpackLow(pair4.AsInt16(), pair6.AsInt16());
+        Vector128<short> quad5 = Vector128_.UnpackHigh(pair4.AsInt16(), pair6.AsInt16());
+        Vector128<int> columns01 = Vector128_.UnpackLow(quad0.AsInt32(), quad4.AsInt32());
+        Vector128<int> columns23 = Vector128_.UnpackHigh(quad0.AsInt32(), quad4.AsInt32());
+        Vector128<int> columns45 = Vector128_.UnpackLow(quad1.AsInt32(), quad5.AsInt32());
+        Vector128<int> columns67 = Vector128_.UnpackHigh(quad1.AsInt32(), quad5.AsInt32());
+
+        StoreEightBytes(columns01.AsUInt64().GetElement(0), ref destinationBase, ((x + 0) * destinationStride) + y);
+        StoreEightBytes(columns01.AsUInt64().GetElement(1), ref destinationBase, ((x + 1) * destinationStride) + y);
+        StoreEightBytes(columns23.AsUInt64().GetElement(0), ref destinationBase, ((x + 2) * destinationStride) + y);
+        StoreEightBytes(columns23.AsUInt64().GetElement(1), ref destinationBase, ((x + 3) * destinationStride) + y);
+        StoreEightBytes(columns45.AsUInt64().GetElement(0), ref destinationBase, ((x + 4) * destinationStride) + y);
+        StoreEightBytes(columns45.AsUInt64().GetElement(1), ref destinationBase, ((x + 5) * destinationStride) + y);
+        StoreEightBytes(columns67.AsUInt64().GetElement(0), ref destinationBase, ((x + 6) * destinationStride) + y);
+        StoreEightBytes(columns67.AsUInt64().GetElement(1), ref destinationBase, ((x + 7) * destinationStride) + y);
+    }
+
+    /// <summary>
+    /// Transposes one four-by-four tile of 8-bit prediction samples.
+    /// </summary>
+    /// <param name="source">The contiguous source block.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="sourceStride">The source row stride.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="x">The tile X coordinate.</param>
+    /// <param name="y">The tile Y coordinate.</param>
+    private static void Transpose4x4(ReadOnlySpan<byte> source, Span<byte> destination, int sourceStride, int destinationStride, int x, int y)
+    {
+        ref byte sourceBase = ref MemoryMarshal.GetReference(source);
+        ref byte destinationBase = ref MemoryMarshal.GetReference(destination);
+        Vector128<byte> row0 = LoadFourBytes(ref sourceBase, ((y + 0) * sourceStride) + x);
+        Vector128<byte> row1 = LoadFourBytes(ref sourceBase, ((y + 1) * sourceStride) + x);
+        Vector128<byte> row2 = LoadFourBytes(ref sourceBase, ((y + 2) * sourceStride) + x);
+        Vector128<byte> row3 = LoadFourBytes(ref sourceBase, ((y + 3) * sourceStride) + x);
+        Vector128<byte> pair0 = Vector128_.UnpackLow(row0, row1);
+        Vector128<byte> pair1 = Vector128_.UnpackLow(row2, row3);
+        Vector128<short> columns = Vector128_.UnpackLow(pair0.AsInt16(), pair1.AsInt16());
+
+        Vector128<uint> packedColumns = columns.AsUInt32();
+        StoreFourBytes(packedColumns.GetElement(0), ref destinationBase, ((x + 0) * destinationStride) + y);
+        StoreFourBytes(packedColumns.GetElement(1), ref destinationBase, ((x + 1) * destinationStride) + y);
+        StoreFourBytes(packedColumns.GetElement(2), ref destinationBase, ((x + 2) * destinationStride) + y);
+        StoreFourBytes(packedColumns.GetElement(3), ref destinationBase, ((x + 3) * destinationStride) + y);
+    }
+
+    /// <summary>
+    /// Transposes one eight-by-eight tile of high-bit-depth prediction samples.
+    /// </summary>
+    /// <param name="source">The contiguous source block.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="sourceStride">The source row stride.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="x">The tile X coordinate.</param>
+    /// <param name="y">The tile Y coordinate.</param>
+    private static void Transpose8x8(ReadOnlySpan<short> source, Span<short> destination, int sourceStride, int destinationStride, int x, int y)
+    {
+        ref short sourceBase = ref MemoryMarshal.GetReference(source);
+        ref short destinationBase = ref MemoryMarshal.GetReference(destination);
+        Vector128<short> row0 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 0) * sourceStride) + x));
+        Vector128<short> row1 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 1) * sourceStride) + x));
+        Vector128<short> row2 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 2) * sourceStride) + x));
+        Vector128<short> row3 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 3) * sourceStride) + x));
+        Vector128<short> row4 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 4) * sourceStride) + x));
+        Vector128<short> row5 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 5) * sourceStride) + x));
+        Vector128<short> row6 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 6) * sourceStride) + x));
+        Vector128<short> row7 = Vector128.LoadUnsafe(ref sourceBase, (nuint)(((y + 7) * sourceStride) + x));
+        Vector128<short> pair0 = Vector128_.UnpackLow(row0, row1);
+        Vector128<short> pair1 = Vector128_.UnpackHigh(row0, row1);
+        Vector128<short> pair2 = Vector128_.UnpackLow(row2, row3);
+        Vector128<short> pair3 = Vector128_.UnpackHigh(row2, row3);
+        Vector128<short> pair4 = Vector128_.UnpackLow(row4, row5);
+        Vector128<short> pair5 = Vector128_.UnpackHigh(row4, row5);
+        Vector128<short> pair6 = Vector128_.UnpackLow(row6, row7);
+        Vector128<short> pair7 = Vector128_.UnpackHigh(row6, row7);
+        Vector128<int> quad0 = Vector128_.UnpackLow(pair0.AsInt32(), pair2.AsInt32());
+        Vector128<int> quad1 = Vector128_.UnpackHigh(pair0.AsInt32(), pair2.AsInt32());
+        Vector128<int> quad2 = Vector128_.UnpackLow(pair1.AsInt32(), pair3.AsInt32());
+        Vector128<int> quad3 = Vector128_.UnpackHigh(pair1.AsInt32(), pair3.AsInt32());
+        Vector128<int> quad4 = Vector128_.UnpackLow(pair4.AsInt32(), pair6.AsInt32());
+        Vector128<int> quad5 = Vector128_.UnpackHigh(pair4.AsInt32(), pair6.AsInt32());
+        Vector128<int> quad6 = Vector128_.UnpackLow(pair5.AsInt32(), pair7.AsInt32());
+        Vector128<int> quad7 = Vector128_.UnpackHigh(pair5.AsInt32(), pair7.AsInt32());
+        Vector128<short> column0 = Vector128_.UnpackLow(quad0.AsInt64(), quad4.AsInt64()).AsInt16();
+        Vector128<short> column1 = Vector128_.UnpackHigh(quad0.AsInt64(), quad4.AsInt64()).AsInt16();
+        Vector128<short> column2 = Vector128_.UnpackLow(quad1.AsInt64(), quad5.AsInt64()).AsInt16();
+        Vector128<short> column3 = Vector128_.UnpackHigh(quad1.AsInt64(), quad5.AsInt64()).AsInt16();
+        Vector128<short> column4 = Vector128_.UnpackLow(quad2.AsInt64(), quad6.AsInt64()).AsInt16();
+        Vector128<short> column5 = Vector128_.UnpackHigh(quad2.AsInt64(), quad6.AsInt64()).AsInt16();
+        Vector128<short> column6 = Vector128_.UnpackLow(quad3.AsInt64(), quad7.AsInt64()).AsInt16();
+        Vector128<short> column7 = Vector128_.UnpackHigh(quad3.AsInt64(), quad7.AsInt64()).AsInt16();
+        column0.StoreUnsafe(ref destinationBase, (nuint)(((x + 0) * destinationStride) + y));
+        column1.StoreUnsafe(ref destinationBase, (nuint)(((x + 1) * destinationStride) + y));
+        column2.StoreUnsafe(ref destinationBase, (nuint)(((x + 2) * destinationStride) + y));
+        column3.StoreUnsafe(ref destinationBase, (nuint)(((x + 3) * destinationStride) + y));
+        column4.StoreUnsafe(ref destinationBase, (nuint)(((x + 4) * destinationStride) + y));
+        column5.StoreUnsafe(ref destinationBase, (nuint)(((x + 5) * destinationStride) + y));
+        column6.StoreUnsafe(ref destinationBase, (nuint)(((x + 6) * destinationStride) + y));
+        column7.StoreUnsafe(ref destinationBase, (nuint)(((x + 7) * destinationStride) + y));
+    }
+
+    /// <summary>
+    /// Transposes one four-by-four tile of high-bit-depth prediction samples.
+    /// </summary>
+    /// <param name="source">The contiguous source block.</param>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="sourceStride">The source row stride.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="x">The tile X coordinate.</param>
+    /// <param name="y">The tile Y coordinate.</param>
+    private static void Transpose4x4(ReadOnlySpan<short> source, Span<short> destination, int sourceStride, int destinationStride, int x, int y)
+    {
+        ref short sourceBase = ref MemoryMarshal.GetReference(source);
+        ref short destinationBase = ref MemoryMarshal.GetReference(destination);
+        Vector128<short> row0 = LoadFourShorts(ref sourceBase, ((y + 0) * sourceStride) + x);
+        Vector128<short> row1 = LoadFourShorts(ref sourceBase, ((y + 1) * sourceStride) + x);
+        Vector128<short> row2 = LoadFourShorts(ref sourceBase, ((y + 2) * sourceStride) + x);
+        Vector128<short> row3 = LoadFourShorts(ref sourceBase, ((y + 3) * sourceStride) + x);
+        Vector128<short> pair0 = Vector128_.UnpackLow(row0, row1);
+        Vector128<short> pair1 = Vector128_.UnpackLow(row2, row3);
+        Vector128<int> columns01 = Vector128_.UnpackLow(pair0.AsInt32(), pair1.AsInt32());
+        Vector128<int> columns23 = Vector128_.UnpackHigh(pair0.AsInt32(), pair1.AsInt32());
+
+        StoreFourShorts(columns01.AsUInt64().GetElement(0), ref destinationBase, ((x + 0) * destinationStride) + y);
+        StoreFourShorts(columns01.AsUInt64().GetElement(1), ref destinationBase, ((x + 1) * destinationStride) + y);
+        StoreFourShorts(columns23.AsUInt64().GetElement(0), ref destinationBase, ((x + 2) * destinationStride) + y);
+        StoreFourShorts(columns23.AsUInt64().GetElement(1), ref destinationBase, ((x + 3) * destinationStride) + y);
+    }
+
+    /// <summary>
+    /// Loads eight bytes into the lower half of a vector without reading past a tile row.
+    /// </summary>
+    /// <param name="source">The source buffer origin.</param>
+    /// <param name="offset">The source offset.</param>
+    /// <returns>The loaded bytes.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<byte> LoadEightBytes(ref byte source, int offset)
+        => Vector128.Create(Unsafe.As<byte, ulong>(ref Unsafe.Add(ref source, offset)), 0UL).AsByte();
+
+    /// <summary>
+    /// Loads four bytes into the low vector lanes without reading past a tile row.
+    /// </summary>
+    /// <param name="source">The source buffer origin.</param>
+    /// <param name="offset">The source offset.</param>
+    /// <returns>The loaded bytes.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<byte> LoadFourBytes(ref byte source, int offset)
+        => Vector128.Create(Unsafe.As<byte, uint>(ref Unsafe.Add(ref source, offset)), 0U, 0U, 0U).AsByte();
+
+    /// <summary>
+    /// Loads four high-bit-depth samples into the lower half of a vector without reading past a tile row.
+    /// </summary>
+    /// <param name="source">The source buffer origin.</param>
+    /// <param name="offset">The source offset.</param>
+    /// <returns>The loaded samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<short> LoadFourShorts(ref short source, int offset)
+        => Vector128.Create(Unsafe.As<short, ulong>(ref Unsafe.Add(ref source, offset)), 0UL).AsInt16();
+
+    /// <summary>
+    /// Stores the lower eight bytes of a vector.
+    /// </summary>
+    /// <param name="source">The packed bytes.</param>
+    /// <param name="destination">The destination buffer origin.</param>
+    /// <param name="offset">The destination offset.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void StoreEightBytes(ulong source, ref byte destination, int offset)
+        => Unsafe.As<byte, ulong>(ref Unsafe.Add(ref destination, offset)) = source;
+
+    /// <summary>
+    /// Stores four bytes from the low vector lanes.
+    /// </summary>
+    /// <param name="source">The packed bytes.</param>
+    /// <param name="destination">The destination buffer origin.</param>
+    /// <param name="offset">The destination offset.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void StoreFourBytes(uint source, ref byte destination, int offset)
+        => Unsafe.As<byte, uint>(ref Unsafe.Add(ref destination, offset)) = source;
+
+    /// <summary>
+    /// Stores four high-bit-depth samples from the low vector lanes.
+    /// </summary>
+    /// <param name="source">The packed samples.</param>
+    /// <param name="destination">The destination buffer origin.</param>
+    /// <param name="offset">The destination offset.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static void StoreFourShorts(ulong source, ref short destination, int offset)
+        => Unsafe.As<short, ulong>(ref Unsafe.Add(ref destination, offset)) = source;
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DirectionalIntraPredictor.cs

@@ -0,0 +1,443 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+/// <summary>
+/// Reconstructs AV1 directional intra-prediction blocks from prepared neighboring samples.
+/// </summary>
+/// <remarks>
+/// The three projection zones implement the directional prediction process in section 7.11.2.4 of the AV1 specification.
+/// </remarks>
+internal static partial class Av1DirectionalIntraPredictor
+{
+    /// <summary>
+    /// The largest number of samples required to transpose a directional prediction block.
+    /// </summary>
+    public const int ScratchLength = 64 * 64;
+
+    /// <summary>
+    /// Gets the Q8 directional derivatives indexed by acute prediction angle.
+    /// </summary>
+    private static ReadOnlySpan<int> DirectionalIntraDerivative =>
+    [
+
+        // Zero entries represent angles which AV1 never signals. Direct indexing avoids a search or division in
+        // each directional block while retaining the exact fixed-point projections from the normative table.
+        0, 0, 0, 1023, 0, 0, 547, 0, 0, 372, 0, 0, 0, 0, 273, 0, 0, 215, 0, 0, 178, 0, 0,
+        151, 0, 0, 132, 0, 0, 116, 0, 0, 102, 0, 0, 0, 90, 0, 0, 80, 0, 0, 71, 0, 0, 64, 0, 0,
+        57, 0, 0, 51, 0, 0, 45, 0, 0, 0, 40, 0, 0, 35, 0, 0, 31, 0, 0, 27, 0, 0, 23, 0, 0,
+        19, 0, 0, 15, 0, 0, 0, 0, 11, 0, 0, 7, 0, 0, 3, 0, 0,
+    ];
+
+    /// <summary>
+    /// Predicts an 8-bit directional block using the widest available SIMD path.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="transformSize">The predicted block dimensions.</param>
+    /// <param name="above">The prepared top reference, including any required extension.</param>
+    /// <param name="left">The prepared left reference, including any required extension.</param>
+    /// <param name="upsampleAbove">Whether the top edge contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left edge contains half-sample positions.</param>
+    /// <param name="angle">The adjusted prediction angle.</param>
+    /// <param name="scratch">The caller-owned block transposition workspace.</param>
+    public static void Predict(Span<byte> destination, int destinationStride, Av1TransformSize transformSize, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, bool upsampleAbove, bool upsampleLeft, int angle, Span<byte> scratch)
+    {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+
+        if (angle is > 0 and < 90)
+        {
+            PredictZone1(destination, destinationStride, above, upsampleAbove, GetDeltaX(angle), width, height);
+        }
+        else if (angle is > 90 and < 180)
+        {
+            PredictZone2(destination, destinationStride, above, left, upsampleAbove, upsampleLeft, GetDeltaX(angle), GetDeltaY(angle), width, height);
+        }
+        else if (angle is > 180 and < 270)
+        {
+            // libaom computes zone 3 as a zone 1 block with swapped dimensions, then transposes it. This preserves
+            // contiguous reference reads and destination stores in both hot stages instead of scattering columns.
+            Span<byte> transposed = scratch[..(width * height)];
+            PredictZone1(transposed, height, left, upsampleLeft, GetDeltaY(angle), height, width);
+            Transpose(transposed, destination, height, width, destinationStride);
+        }
+        else
+        {
+            Av1PredictionMode mode = angle == 90 ? Av1PredictionMode.Vertical : Av1PredictionMode.Horizontal;
+            Av1IntraPredictorBase.GetPredictor(mode).Predict(destination, destinationStride, above, left, width, height);
+        }
+    }
+
+    /// <summary>
+    /// Predicts a high-bit-depth directional block using the widest available SIMD path.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="transformSize">The predicted block dimensions.</param>
+    /// <param name="above">The prepared top reference, including any required extension.</param>
+    /// <param name="left">The prepared left reference, including any required extension.</param>
+    /// <param name="upsampleAbove">Whether the top edge contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left edge contains half-sample positions.</param>
+    /// <param name="angle">The adjusted prediction angle.</param>
+    /// <param name="scratch">The caller-owned block transposition workspace.</param>
+    public static void Predict(Span<short> destination, int destinationStride, Av1TransformSize transformSize, ReadOnlySpan<short> above, ReadOnlySpan<short> left, bool upsampleAbove, bool upsampleLeft, int angle, Span<short> scratch)
+    {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+
+        if (angle is > 0 and < 90)
+        {
+            PredictZone1(destination, destinationStride, above, upsampleAbove, GetDeltaX(angle), width, height);
+        }
+        else if (angle is > 90 and < 180)
+        {
+            PredictZone2(destination, destinationStride, above, left, upsampleAbove, upsampleLeft, GetDeltaX(angle), GetDeltaY(angle), width, height);
+        }
+        else if (angle is > 180 and < 270)
+        {
+            Span<short> transposed = scratch[..(width * height)];
+            PredictZone1(transposed, height, left, upsampleLeft, GetDeltaY(angle), height, width);
+            Transpose(transposed, destination, height, width, destinationStride);
+        }
+        else
+        {
+            Av1PredictionMode mode = angle == 90 ? Av1PredictionMode.Vertical : Av1PredictionMode.Horizontal;
+            Av1IntraPredictorBase.GetPredictor(mode).Predict(destination, destinationStride, above, left, width, height);
+        }
+    }
+
+    /// <summary>
+    /// Predicts an 8-bit directional block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="transformSize">The predicted block dimensions.</param>
+    /// <param name="above">The prepared top reference, including any required extension.</param>
+    /// <param name="left">The prepared left reference, including any required extension.</param>
+    /// <param name="upsampleAbove">Whether the top edge contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left edge contains half-sample positions.</param>
+    /// <param name="angle">The adjusted prediction angle.</param>
+    public static void PredictScalar(Span<byte> destination, int destinationStride, Av1TransformSize transformSize, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, bool upsampleAbove, bool upsampleLeft, int angle)
+    {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+
+        if (angle is > 0 and < 90)
+        {
+            PredictZone1Scalar(destination, destinationStride, above, upsampleAbove, GetDeltaX(angle), width, height);
+        }
+        else if (angle is > 90 and < 180)
+        {
+            PredictZone2Scalar(destination, destinationStride, above, left, upsampleAbove, upsampleLeft, GetDeltaX(angle), GetDeltaY(angle), width, height);
+        }
+        else if (angle is > 180 and < 270)
+        {
+            PredictZone3Scalar(destination, destinationStride, left, upsampleLeft, GetDeltaY(angle), width, height);
+        }
+        else
+        {
+            Av1PredictionMode mode = angle == 90 ? Av1PredictionMode.Vertical : Av1PredictionMode.Horizontal;
+            Av1IntraPredictorBase.GetPredictor(mode).PredictScalar(destination, destinationStride, above, left, width, height);
+        }
+    }
+
+    /// <summary>
+    /// Predicts a high-bit-depth directional block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="transformSize">The predicted block dimensions.</param>
+    /// <param name="above">The prepared top reference, including any required extension.</param>
+    /// <param name="left">The prepared left reference, including any required extension.</param>
+    /// <param name="upsampleAbove">Whether the top edge contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left edge contains half-sample positions.</param>
+    /// <param name="angle">The adjusted prediction angle.</param>
+    public static void PredictScalar(Span<short> destination, int destinationStride, Av1TransformSize transformSize, ReadOnlySpan<short> above, ReadOnlySpan<short> left, bool upsampleAbove, bool upsampleLeft, int angle)
+    {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+
+        if (angle is > 0 and < 90)
+        {
+            PredictZone1Scalar(destination, destinationStride, above, upsampleAbove, GetDeltaX(angle), width, height);
+        }
+        else if (angle is > 90 and < 180)
+        {
+            PredictZone2Scalar(destination, destinationStride, above, left, upsampleAbove, upsampleLeft, GetDeltaX(angle), GetDeltaY(angle), width, height);
+        }
+        else if (angle is > 180 and < 270)
+        {
+            PredictZone3Scalar(destination, destinationStride, left, upsampleLeft, GetDeltaY(angle), width, height);
+        }
+        else
+        {
+            Av1PredictionMode mode = angle == 90 ? Av1PredictionMode.Vertical : Av1PredictionMode.Horizontal;
+            Av1IntraPredictorBase.GetPredictor(mode).PredictScalar(destination, destinationStride, above, left, width, height);
+        }
+    }
+
+    /// <summary>
+    /// Gets the horizontal Q8 projection derivative for an adjusted angle.
+    /// </summary>
+    /// <param name="angle">The adjusted prediction angle.</param>
+    /// <returns>The horizontal derivative, or one when the selected zone does not consume it.</returns>
+    public static int GetDeltaX(int angle)
+        => angle switch
+        {
+            > 0 and < 90 => DirectionalIntraDerivative[angle],
+            > 90 and < 180 => DirectionalIntraDerivative[180 - angle],
+            _ => 1,
+        };
+
+    /// <summary>
+    /// Gets the vertical Q8 projection derivative for an adjusted angle.
+    /// </summary>
+    /// <param name="angle">The adjusted prediction angle.</param>
+    /// <returns>The vertical derivative, or one when the selected zone does not consume it.</returns>
+    public static int GetDeltaY(int angle)
+        => angle switch
+        {
+            > 90 and < 180 => DirectionalIntraDerivative[angle - 90],
+            > 180 and < 270 => DirectionalIntraDerivative[270 - angle],
+            _ => 1,
+        };
+
+    /// <summary>
+    /// Predicts one 8-bit zone 1 block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="upsample">Whether the reference contains half-sample positions.</param>
+    /// <param name="derivative">The Q8 projection derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone1Scalar(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, bool upsample, int derivative, int width, int height)
+    {
+        int upsampleShift = upsample ? 1 : 0;
+        int maximumBasis = (width + height - 1) << upsampleShift;
+        int fractionBits = 6 - upsampleShift;
+        int basisIncrement = 1 << upsampleShift;
+        int projection = derivative;
+        ref byte aboveBase = ref Unsafe.AsRef(in above[0]);
+
+        for (int row = 0; row < height; row++, projection += derivative)
+        {
+            int basis = projection >> fractionBits;
+            int weight = ((projection << upsampleShift) & 0x3F) >> 1;
+            ref byte destinationRow = ref destination[row * destinationStride];
+
+            for (int column = 0; column < width; column++, basis += basisIncrement)
+            {
+                Unsafe.Add(ref destinationRow, column) = basis < maximumBasis
+                    ? (byte)(((Unsafe.Add(ref aboveBase, basis) * (32 - weight)) + (Unsafe.Add(ref aboveBase, basis + 1) * weight) + 16) >> 5)
+                    : Unsafe.Add(ref aboveBase, maximumBasis);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Predicts one high-bit-depth zone 1 block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="upsample">Whether the reference contains half-sample positions.</param>
+    /// <param name="derivative">The Q8 projection derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone1Scalar(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, bool upsample, int derivative, int width, int height)
+    {
+        int upsampleShift = upsample ? 1 : 0;
+        int maximumBasis = (width + height - 1) << upsampleShift;
+        int fractionBits = 6 - upsampleShift;
+        int basisIncrement = 1 << upsampleShift;
+        int projection = derivative;
+        ref short aboveBase = ref Unsafe.AsRef(in above[0]);
+
+        for (int row = 0; row < height; row++, projection += derivative)
+        {
+            int basis = projection >> fractionBits;
+            int weight = ((projection << upsampleShift) & 0x3F) >> 1;
+            ref short destinationRow = ref destination[row * destinationStride];
+
+            for (int column = 0; column < width; column++, basis += basisIncrement)
+            {
+                Unsafe.Add(ref destinationRow, column) = basis < maximumBasis
+                    ? (short)(((Unsafe.Add(ref aboveBase, basis) * (32 - weight)) + (Unsafe.Add(ref aboveBase, basis + 1) * weight) + 16) >> 5)
+                    : Unsafe.Add(ref aboveBase, maximumBasis);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Predicts one 8-bit zone 2 block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="upsampleAbove">Whether the top reference contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left reference contains half-sample positions.</param>
+    /// <param name="dx">The horizontal Q8 derivative.</param>
+    /// <param name="dy">The vertical Q8 derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone2Scalar(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, bool upsampleAbove, bool upsampleLeft, int dx, int dy, int width, int height)
+    {
+        int aboveShift = upsampleAbove ? 1 : 0;
+        int leftShift = upsampleLeft ? 1 : 0;
+        int minimumTopBasis = -(1 << aboveShift);
+        int topFractionBits = 6 - aboveShift;
+        int leftFractionBits = 6 - leftShift;
+        int topBasisIncrement = 1 << aboveShift;
+        int topProjection = -dx;
+        ref byte aboveBase = ref Unsafe.AsRef(in above[0]);
+        ref byte leftBase = ref Unsafe.AsRef(in left[0]);
+
+        for (int row = 0; row < height; row++, topProjection -= dx)
+        {
+            int topBasis = topProjection >> topFractionBits;
+            int topWeight = ((topProjection << aboveShift) & 0x3F) >> 1;
+            int leftProjection = (row << 6) - dy;
+            ref byte destinationRow = ref destination[row * destinationStride];
+
+            for (int column = 0; column < width; column++, topBasis += topBasisIncrement, leftProjection -= dy)
+            {
+                int prediction;
+                if (topBasis >= minimumTopBasis)
+                {
+                    prediction = (Unsafe.Add(ref aboveBase, topBasis) * (32 - topWeight)) + (Unsafe.Add(ref aboveBase, topBasis + 1) * topWeight);
+                }
+                else
+                {
+                    int leftBasis = leftProjection >> leftFractionBits;
+                    int leftWeight = ((leftProjection << leftShift) & 0x3F) >> 1;
+                    prediction = (Unsafe.Add(ref leftBase, leftBasis) * (32 - leftWeight)) + (Unsafe.Add(ref leftBase, leftBasis + 1) * leftWeight);
+                }
+
+                Unsafe.Add(ref destinationRow, column) = (byte)((prediction + 16) >> 5);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Predicts one high-bit-depth zone 2 block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="above">The projected top reference.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="upsampleAbove">Whether the top reference contains half-sample positions.</param>
+    /// <param name="upsampleLeft">Whether the left reference contains half-sample positions.</param>
+    /// <param name="dx">The horizontal Q8 derivative.</param>
+    /// <param name="dy">The vertical Q8 derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone2Scalar(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, bool upsampleAbove, bool upsampleLeft, int dx, int dy, int width, int height)
+    {
+        int aboveShift = upsampleAbove ? 1 : 0;
+        int leftShift = upsampleLeft ? 1 : 0;
+        int minimumTopBasis = -(1 << aboveShift);
+        int topFractionBits = 6 - aboveShift;
+        int leftFractionBits = 6 - leftShift;
+        int topBasisIncrement = 1 << aboveShift;
+        int topProjection = -dx;
+        ref short aboveBase = ref Unsafe.AsRef(in above[0]);
+        ref short leftBase = ref Unsafe.AsRef(in left[0]);
+
+        for (int row = 0; row < height; row++, topProjection -= dx)
+        {
+            int topBasis = topProjection >> topFractionBits;
+            int topWeight = ((topProjection << aboveShift) & 0x3F) >> 1;
+            int leftProjection = (row << 6) - dy;
+            ref short destinationRow = ref destination[row * destinationStride];
+
+            for (int column = 0; column < width; column++, topBasis += topBasisIncrement, leftProjection -= dy)
+            {
+                int prediction;
+                if (topBasis >= minimumTopBasis)
+                {
+                    prediction = (Unsafe.Add(ref aboveBase, topBasis) * (32 - topWeight)) + (Unsafe.Add(ref aboveBase, topBasis + 1) * topWeight);
+                }
+                else
+                {
+                    int leftBasis = leftProjection >> leftFractionBits;
+                    int leftWeight = ((leftProjection << leftShift) & 0x3F) >> 1;
+                    prediction = (Unsafe.Add(ref leftBase, leftBasis) * (32 - leftWeight)) + (Unsafe.Add(ref leftBase, leftBasis + 1) * leftWeight);
+                }
+
+                Unsafe.Add(ref destinationRow, column) = (short)((prediction + 16) >> 5);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Predicts one 8-bit zone 3 block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="upsample">Whether the reference contains half-sample positions.</param>
+    /// <param name="derivative">The Q8 projection derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone3Scalar(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> left, bool upsample, int derivative, int width, int height)
+    {
+        int upsampleShift = upsample ? 1 : 0;
+        int maximumBasis = (width + height - 1) << upsampleShift;
+        int fractionBits = 6 - upsampleShift;
+        int basisIncrement = 1 << upsampleShift;
+        int projection = derivative;
+        ref byte leftBase = ref Unsafe.AsRef(in left[0]);
+
+        for (int column = 0; column < width; column++, projection += derivative)
+        {
+            int basis = projection >> fractionBits;
+            int weight = ((projection << upsampleShift) & 0x3F) >> 1;
+            for (int row = 0; row < height; row++, basis += basisIncrement)
+            {
+                destination[(row * destinationStride) + column] = basis < maximumBasis
+                    ? (byte)(((Unsafe.Add(ref leftBase, basis) * (32 - weight)) + (Unsafe.Add(ref leftBase, basis + 1) * weight) + 16) >> 5)
+                    : Unsafe.Add(ref leftBase, maximumBasis);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Predicts one high-bit-depth zone 3 block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride.</param>
+    /// <param name="left">The projected left reference.</param>
+    /// <param name="upsample">Whether the reference contains half-sample positions.</param>
+    /// <param name="derivative">The Q8 projection derivative.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    private static void PredictZone3Scalar(Span<short> destination, int destinationStride, ReadOnlySpan<short> left, bool upsample, int derivative, int width, int height)
+    {
+        int upsampleShift = upsample ? 1 : 0;
+        int maximumBasis = (width + height - 1) << upsampleShift;
+        int fractionBits = 6 - upsampleShift;
+        int basisIncrement = 1 << upsampleShift;
+        int projection = derivative;
+        ref short leftBase = ref Unsafe.AsRef(in left[0]);
+
+        for (int column = 0; column < width; column++, projection += derivative)
+        {
+            int basis = projection >> fractionBits;
+            int weight = ((projection << upsampleShift) & 0x3F) >> 1;
+            for (int row = 0; row < height; row++, basis += basisIncrement)
+            {
+                destination[(row * destinationStride) + column] = basis < maximumBasis
+                    ? (short)(((Unsafe.Add(ref leftBase, basis) * (32 - weight)) + (Unsafe.Add(ref leftBase, basis + 1) * weight) + 16) >> 5)
+                    : Unsafe.Add(ref leftBase, maximumBasis);
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DirectionalZone1Predictor.cs

@@ -1,118 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Produces 8-bit AV1 directional intra predictions for angles in zone 1.
-/// </summary>
-/// <remarks>
-/// Zone 1 projects the top reference samples into the block for prediction angles less than 90 degrees.
-/// The scalar prediction follows the directional prediction process in section 7.11.2.4 of the AV1 specification.
-/// </remarks>
-internal readonly struct Av1DirectionalZone1Predictor
-{
-    /// <summary>
-    /// The width of the prediction block in samples.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The height of the prediction block in samples.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DirectionalZone1Predictor"/> struct for the specified block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The dimensions of the prediction block.</param>
-    public Av1DirectionalZone1Predictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DirectionalZone1Predictor"/> struct for the specified transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    public Av1DirectionalZone1Predictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Produces an 8-bit zone 1 directional prediction for a transform block.
-    /// </summary>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top reference samples, including any required extension.</param>
-    /// <param name="upsampleAbove">A value indicating whether the top reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative in Q6 precision.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, bool upsampleAbove, int dx)
-        => new Av1DirectionalZone1Predictor(transformSize).PredictScalar(destination, stride, above, upsampleAbove, dx);
-
-    /// <summary>
-    /// Produces an 8-bit zone 1 directional prediction for this block.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top reference samples, including any required extension.</param>
-    /// <param name="upsample">A value indicating whether the top reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative in Q6 precision.</param>
-    /// <remarks>Corresponds to <c>svt_av1_dr_prediction_z1_c</c> in SVT-AV1.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, bool upsample, int dx)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        int upsampleAbove = upsample ? 1 : 0;
-        ref byte aboveRef = ref above[0];
-        ref byte destinationRef = ref destination[0];
-        int maxBasisX = (((int)this.blockWidth + (int)this.blockHeight) - 1) << upsampleAbove;
-        int fractionBitCount = 6 - upsampleAbove;
-        int basisIncrement = 1 << upsampleAbove;
-        int x = dx;
-        for (nuint r = 0; r < this.blockHeight; ++r)
-        {
-            // AV1 retains six fractional projection bits, or five after reference upsampling.
-            // The interpolation weights sum to 32 because the low projection bit is discarded.
-            int basis = x >> fractionBitCount, shift = ((x << upsampleAbove) & 0x3F) >> 1;
-
-            if (basis >= maxBasisX)
-            {
-                for (nuint i = r; i < this.blockHeight; ++i)
-                {
-                    Unsafe.InitBlock(ref destinationRef, Unsafe.Add(ref aboveRef, maxBasisX), (uint)this.blockWidth);
-                    destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-                }
-
-                return;
-            }
-
-            for (nuint c = 0; c < this.blockWidth; ++c)
-            {
-                if (basis < maxBasisX)
-                {
-                    int val;
-                    val = (Unsafe.Add(ref aboveRef, basis) * (32 - shift)) + (Unsafe.Add(ref aboveRef, basis + 1) * shift);
-                    val = Av1Math.RoundPowerOf2(val, 5);
-                    Unsafe.Add(ref destinationRef, c) = (byte)Av1Math.Clamp(val, 0, 255);
-                }
-                else
-                {
-                    Unsafe.Add(ref destinationRef, c) = Unsafe.Add(ref aboveRef, maxBasisX);
-                }
-
-                basis += basisIncrement;
-            }
-
-            x += dx;
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DirectionalZone2Predictor.cs

@@ -1,124 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System;
-using System.Runtime.CompilerServices;
-using System.Security.Cryptography;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Produces 8-bit AV1 directional intra predictions for angles in zone 2.
-/// </summary>
-/// <remarks>
-/// Zone 2 projects both top and left reference samples into the block for prediction angles between 90 and 180 degrees.
-/// The scalar prediction follows the directional prediction process in section 7.11.2.4 of the AV1 specification.
-/// </remarks>
-internal readonly struct Av1DirectionalZone2Predictor
-{
-    /// <summary>
-    /// The width of the prediction block in samples.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The height of the prediction block in samples.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DirectionalZone2Predictor"/> struct for the specified block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The dimensions of the prediction block.</param>
-    public Av1DirectionalZone2Predictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DirectionalZone2Predictor"/> struct for the specified transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    public Av1DirectionalZone2Predictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Produces an 8-bit zone 2 directional prediction for a transform block.
-    /// </summary>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top reference samples, including any required extension.</param>
-    /// <param name="left">The left reference samples, including any required extension.</param>
-    /// <param name="upsampleAbove">A value indicating whether the top reference samples were upsampled.</param>
-    /// <param name="upsampleLeft">A value indicating whether the left reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative in Q6 precision.</param>
-    /// <param name="dy">The vertical projection derivative in Q6 precision.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left, bool upsampleAbove, bool upsampleLeft, int dx, int dy)
-        => new Av1DirectionalZone2Predictor(transformSize).PredictScalar(destination, stride, above, left, upsampleAbove, upsampleLeft, dx, dy);
-
-    /// <summary>
-    /// Produces an 8-bit zone 2 directional prediction for this block.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top reference samples, including any required extension.</param>
-    /// <param name="left">The left reference samples, including any required extension.</param>
-    /// <param name="doUpsampleAbove">A value indicating whether the top reference samples were upsampled.</param>
-    /// <param name="doUpsampleLeft">A value indicating whether the left reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative in Q6 precision.</param>
-    /// <param name="dy">The vertical projection derivative in Q6 precision.</param>
-    /// <remarks>Corresponds to <c>svt_av1_dr_prediction_z2_c</c> in SVT-AV1.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left, bool doUpsampleAbove, bool doUpsampleLeft, int dx, int dy)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        int upsampleAbove = doUpsampleAbove ? 1 : 0;
-        int upsampleLeft = doUpsampleLeft ? 1 : 0;
-        ref byte aboveRef = ref above[0];
-        ref byte leftRef = ref left[0];
-        ref byte destinationRef = ref destination[0];
-        int minBasisX = -(1 << upsampleAbove);
-        int fractionBitCountX = 6 - upsampleAbove;
-        int fractionBitCountY = 6 - upsampleLeft;
-        int basisIncrementX = 1 << upsampleAbove;
-        int x = -dx;
-        for (nuint r = 0; r < this.blockHeight; ++r)
-        {
-            int val;
-            int base1 = x >> fractionBitCountX;
-            int y = ((int)r << 6) - dy;
-            for (nuint c = 0; c < this.blockWidth; ++c, base1 += basisIncrementX, y -= dy)
-            {
-                // A nonnegative top projection uses the above edge. Once the projection crosses
-                // the top-left corner, the same destination sample is projected from the left edge.
-                if (base1 >= minBasisX)
-                {
-                    int shift1 = ((x * (1 << upsampleAbove)) & 0x3F) >> 1;
-                    val = (Unsafe.Add(ref aboveRef, base1) * (32 - shift1)) + (Unsafe.Add(ref aboveRef, base1 + 1) * shift1);
-                    val = Av1Math.RoundPowerOf2(val, 5);
-                }
-                else
-                {
-                    int base2 = y >> fractionBitCountY;
-                    Guard.MustBeGreaterThanOrEqualTo(base2, -(1 << upsampleLeft), nameof(base2));
-                    int shift2 = ((y * (1 << upsampleLeft)) & 0x3F) >> 1;
-                    val = (Unsafe.Add(ref leftRef, base2) * (32 - shift2)) + (Unsafe.Add(ref leftRef, base2 + 1) * shift2);
-                    val = Av1Math.RoundPowerOf2(val, 5);
-                }
-
-                Unsafe.Add(ref destinationRef, c) = (byte)Av1Math.Clamp(val, 0, 255);
-            }
-
-            x -= dx;
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1DirectionalZone3Predictor.cs

@@ -1,119 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System;
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Produces 8-bit AV1 directional intra predictions for angles in zone 3.
-/// </summary>
-/// <remarks>
-/// Zone 3 projects the left reference samples into the block for prediction angles greater than 180 degrees.
-/// The scalar prediction follows the directional prediction process in section 7.11.2.4 of the AV1 specification.
-/// </remarks>
-internal readonly struct Av1DirectionalZone3Predictor
-{
-    /// <summary>
-    /// The width of the prediction block in samples.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The height of the prediction block in samples.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DirectionalZone3Predictor"/> struct for the specified block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The dimensions of the prediction block.</param>
-    public Av1DirectionalZone3Predictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1DirectionalZone3Predictor"/> struct for the specified transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    public Av1DirectionalZone3Predictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Produces an 8-bit zone 3 directional prediction for a transform block.
-    /// </summary>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="left">The left reference samples, including any required extension.</param>
-    /// <param name="upsampleLeft">A value indicating whether the left reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative, which must be one in zone 3.</param>
-    /// <param name="dy">The vertical projection derivative in Q6 precision.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> left, bool upsampleLeft, int dx, int dy)
-        => new Av1DirectionalZone3Predictor(transformSize).PredictScalar(destination, stride, left, upsampleLeft, dx, dy);
-
-    /// <summary>
-    /// Produces an 8-bit zone 3 directional prediction for this block.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="left">The left reference samples, including any required extension.</param>
-    /// <param name="upsample">A value indicating whether the left reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative, which must be one in zone 3.</param>
-    /// <param name="dy">The vertical projection derivative in Q6 precision.</param>
-    /// <remarks>Corresponds to <c>svt_av1_dr_prediction_z3_c</c> in SVT-AV1.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> left, bool upsample, int dx, int dy)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        int upsampleLeft = upsample ? 1 : 0;
-        ref byte leftRef = ref left[0];
-        ref byte destinationRef = ref destination[0];
-        Guard.IsTrue(dx == 1, nameof(dx), "Dx expected to be always equal to 1 for directional Zone 3 prediction.");
-        Guard.MustBeGreaterThan(dy, 0, nameof(dy));
-
-        int maxBasisY = ((int)this.blockWidth + (int)this.blockHeight - 1) << upsampleLeft;
-        int fractionBitCount = 6 - upsampleLeft;
-        int basisIncrement = 1 << upsampleLeft;
-        int y = dy;
-        for (nuint c = 0; c < this.blockWidth; ++c)
-        {
-            // Zone 3 is the transpose of zone 1: columns advance along the projected left edge,
-            // while rows advance through the reference samples for each destination column.
-            int basis = y >> fractionBitCount;
-            int shift = ((y << upsampleLeft) & 0x3F) >> 1;
-
-            for (nuint r = 0; r < this.blockHeight; ++r)
-            {
-                if (basis < maxBasisY)
-                {
-                    int val;
-                    val = (Unsafe.Add(ref leftRef, basis) * (32 - shift)) + (Unsafe.Add(ref leftRef, basis + 1) * shift);
-                    val = Av1Math.RoundPowerOf2(val, 5);
-                    Unsafe.Add(ref destinationRef, (r * stride) + c) = (byte)Av1Math.Clamp(val, 0, 255);
-                }
-                else
-                {
-                    for (; r < this.blockHeight; ++r)
-                    {
-                        Unsafe.Add(ref destinationRef, (r * stride) + c) = left[maxBasisY];
-                    }
-
-                    break;
-                }
-
-                basis += basisIncrement;
-            }
-
-            y += dy;
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.DcOperator.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// Defines the AV1 DC filter-intra coefficient operator.
+    /// </summary>
+    internal readonly struct DcOperator : IAv1FilterIntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1FilterIntraMode Mode => Av1FilterIntraMode.DC;
+
+        /// <inheritdoc/>
+        public static ReadOnlySpan<sbyte> Taps =>
+        [
+            -6, 10, 0, 0, 0, 12, 0,
+        -5, 2, 10, 0, 0, 9, 0,
+        -3, 1, 1, 10, 0, 7, 0,
+        -3, 1, 1, 2, 10, 5, 0,
+        -4, 6, 0, 0, 0, 2, 12,
+        -3, 2, 6, 0, 0, 2, 9,
+        -3, 2, 2, 6, 0, 2, 7,
+        -3, 1, 2, 2, 6, 3, 5,
+    ];
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.Directional157Operator.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// Defines the AV1 157-degree directional filter-intra coefficient operator.
+    /// </summary>
+    internal readonly struct Directional157Operator : IAv1FilterIntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1FilterIntraMode Mode => Av1FilterIntraMode.Directional157;
+
+        /// <inheritdoc/>
+        public static ReadOnlySpan<sbyte> Taps =>
+        [
+            -2, 8, 0, 0, 0, 10, 0,
+        -1, 3, 8, 0, 0, 6, 0,
+        -1, 2, 3, 8, 0, 4, 0,
+        0, 1, 2, 3, 8, 2, 0,
+        -1, 4, 0, 0, 0, 3, 10,
+        -1, 3, 4, 0, 0, 4, 6,
+        -1, 2, 3, 4, 0, 4, 4,
+        -1, 2, 2, 3, 4, 3, 3,
+    ];
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.HorizontalOperator.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// Defines the AV1 horizontal filter-intra coefficient operator.
+    /// </summary>
+    internal readonly struct HorizontalOperator : IAv1FilterIntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1FilterIntraMode Mode => Av1FilterIntraMode.Horizontal;
+
+        /// <inheritdoc/>
+        public static ReadOnlySpan<sbyte> Taps =>
+        [
+            -8, 8, 0, 0, 0, 16, 0,
+        -8, 0, 8, 0, 0, 16, 0,
+        -8, 0, 0, 8, 0, 16, 0,
+        -8, 0, 0, 0, 8, 16, 0,
+        -4, 4, 0, 0, 0, 0, 16,
+        -4, 0, 4, 0, 0, 0, 16,
+        -4, 0, 0, 4, 0, 0, 16,
+        -4, 0, 0, 0, 4, 0, 16,
+    ];
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.Operator.cs

@@ -0,0 +1,596 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Intrinsics;
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// Applies one closed filter-intra coefficient operator using the widest useful SIMD width.
+    /// </summary>
+    /// <typeparam name="TOperator">The filter-intra coefficient set.</typeparam>
+    internal sealed class Av1FilterIntraPredictor<TOperator> : Av1FilterIntraPredictorBase
+        where TOperator : struct, IAv1FilterIntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public override Av1FilterIntraMode Mode => TOperator.Mode;
+
+        /// <inheritdoc/>
+        public override void Predict(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height, Span<byte> scratch)
+        {
+            Span<byte> buffer = scratch[..ScratchLength];
+            ref byte bufferBase = ref MemoryMarshal.GetReference(buffer);
+            ref byte aboveBase = ref MemoryMarshal.GetReference(above);
+            ref byte leftBase = ref MemoryMarshal.GetReference(left);
+            ref sbyte taps = ref MemoryMarshal.GetReference(TOperator.Taps);
+            Initialize(buffer, above, left, width, height, Unsafe.Subtract(ref aboveBase, 1));
+
+            if (Vector256.IsHardwareAccelerated)
+            {
+                Vector256<int> tap0 = CreateTapVector256(ref taps, 0);
+                Vector256<int> tap1 = CreateTapVector256(ref taps, 1);
+                Vector256<int> tap2 = CreateTapVector256(ref taps, 2);
+                Vector256<int> tap3 = CreateTapVector256(ref taps, 3);
+                Vector256<int> tap4 = CreateTapVector256(ref taps, 4);
+                Vector256<int> tap5 = CreateTapVector256(ref taps, 5);
+                Vector256<int> tap6 = CreateTapVector256(ref taps, 6);
+                Vector256<int> rounding = Vector256.Create(8);
+                Vector256<int> maximum = Vector256.Create(255);
+
+                for (int row = 1; row <= height; row += 2)
+                {
+                    for (int column = 1; column <= width; column += 4)
+                    {
+                        int sourceOffset = ((row - 1) * BufferStride) + column - 1;
+                        Vector256<int> prediction = Calculate(
+                            tap0,
+                            tap1,
+                            tap2,
+                            tap3,
+                            tap4,
+                            tap5,
+                            tap6,
+                            Unsafe.Add(ref bufferBase, sourceOffset),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 1),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 2),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 3),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 4),
+                            Unsafe.Add(ref bufferBase, sourceOffset + BufferStride),
+                            Unsafe.Add(ref bufferBase, sourceOffset + (2 * BufferStride)));
+
+                        prediction = Vector256.Clamp((prediction + rounding) >> 4, Vector256<int>.Zero, maximum);
+                        StoreEightBytes(prediction, ref bufferBase, (row * BufferStride) + column, ((row + 1) * BufferStride) + column);
+                    }
+                }
+            }
+            else if (Vector128.IsHardwareAccelerated)
+            {
+                Vector128<int> tap0Low = CreateTapVector128(ref taps, 0, 0);
+                Vector128<int> tap1Low = CreateTapVector128(ref taps, 1, 0);
+                Vector128<int> tap2Low = CreateTapVector128(ref taps, 2, 0);
+                Vector128<int> tap3Low = CreateTapVector128(ref taps, 3, 0);
+                Vector128<int> tap4Low = CreateTapVector128(ref taps, 4, 0);
+                Vector128<int> tap5Low = CreateTapVector128(ref taps, 5, 0);
+                Vector128<int> tap6Low = CreateTapVector128(ref taps, 6, 0);
+                Vector128<int> tap0High = CreateTapVector128(ref taps, 0, 4);
+                Vector128<int> tap1High = CreateTapVector128(ref taps, 1, 4);
+                Vector128<int> tap2High = CreateTapVector128(ref taps, 2, 4);
+                Vector128<int> tap3High = CreateTapVector128(ref taps, 3, 4);
+                Vector128<int> tap4High = CreateTapVector128(ref taps, 4, 4);
+                Vector128<int> tap5High = CreateTapVector128(ref taps, 5, 4);
+                Vector128<int> tap6High = CreateTapVector128(ref taps, 6, 4);
+                Vector128<int> rounding = Vector128.Create(8);
+                Vector128<int> maximum = Vector128.Create(255);
+
+                for (int row = 1; row <= height; row += 2)
+                {
+                    for (int column = 1; column <= width; column += 4)
+                    {
+                        int sourceOffset = ((row - 1) * BufferStride) + column - 1;
+                        int p0 = Unsafe.Add(ref bufferBase, sourceOffset);
+                        int p1 = Unsafe.Add(ref bufferBase, sourceOffset + 1);
+                        int p2 = Unsafe.Add(ref bufferBase, sourceOffset + 2);
+                        int p3 = Unsafe.Add(ref bufferBase, sourceOffset + 3);
+                        int p4 = Unsafe.Add(ref bufferBase, sourceOffset + 4);
+                        int p5 = Unsafe.Add(ref bufferBase, sourceOffset + BufferStride);
+                        int p6 = Unsafe.Add(ref bufferBase, sourceOffset + (2 * BufferStride));
+                        Vector128<int> low = Calculate(tap0Low, tap1Low, tap2Low, tap3Low, tap4Low, tap5Low, tap6Low, p0, p1, p2, p3, p4, p5, p6);
+                        Vector128<int> high = Calculate(tap0High, tap1High, tap2High, tap3High, tap4High, tap5High, tap6High, p0, p1, p2, p3, p4, p5, p6);
+                        low = Vector128.Clamp((low + rounding) >> 4, Vector128<int>.Zero, maximum);
+                        high = Vector128.Clamp((high + rounding) >> 4, Vector128<int>.Zero, maximum);
+                        StoreFourBytes(low, ref bufferBase, (row * BufferStride) + column);
+                        StoreFourBytes(high, ref bufferBase, ((row + 1) * BufferStride) + column);
+                    }
+                }
+            }
+            else
+            {
+                PredictGroupsScalar(buffer, width, height, 255, ref taps);
+            }
+
+            CopyToDestination(buffer, destination, destinationStride, width, height);
+        }
+
+        /// <inheritdoc/>
+        public override void Predict(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height, int bitDepth, Span<short> scratch)
+        {
+            Span<short> buffer = scratch[..ScratchLength];
+            ref short bufferBase = ref MemoryMarshal.GetReference(buffer);
+            ref short aboveBase = ref MemoryMarshal.GetReference(above);
+            ref sbyte taps = ref MemoryMarshal.GetReference(TOperator.Taps);
+            Initialize(buffer, above, left, width, height, Unsafe.Subtract(ref aboveBase, 1));
+            int maximum = (1 << bitDepth) - 1;
+
+            if (Vector256.IsHardwareAccelerated)
+            {
+                Vector256<int> tap0 = CreateTapVector256(ref taps, 0);
+                Vector256<int> tap1 = CreateTapVector256(ref taps, 1);
+                Vector256<int> tap2 = CreateTapVector256(ref taps, 2);
+                Vector256<int> tap3 = CreateTapVector256(ref taps, 3);
+                Vector256<int> tap4 = CreateTapVector256(ref taps, 4);
+                Vector256<int> tap5 = CreateTapVector256(ref taps, 5);
+                Vector256<int> tap6 = CreateTapVector256(ref taps, 6);
+                Vector256<int> rounding = Vector256.Create(8);
+                Vector256<int> maximumVector = Vector256.Create(maximum);
+
+                for (int row = 1; row <= height; row += 2)
+                {
+                    for (int column = 1; column <= width; column += 4)
+                    {
+                        int sourceOffset = ((row - 1) * BufferStride) + column - 1;
+                        Vector256<int> prediction = Calculate(
+                            tap0,
+                            tap1,
+                            tap2,
+                            tap3,
+                            tap4,
+                            tap5,
+                            tap6,
+                            Unsafe.Add(ref bufferBase, sourceOffset),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 1),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 2),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 3),
+                            Unsafe.Add(ref bufferBase, sourceOffset + 4),
+                            Unsafe.Add(ref bufferBase, sourceOffset + BufferStride),
+                            Unsafe.Add(ref bufferBase, sourceOffset + (2 * BufferStride)));
+
+                        prediction = Vector256.Clamp((prediction + rounding) >> 4, Vector256<int>.Zero, maximumVector);
+                        StoreEightShorts(prediction, ref bufferBase, (row * BufferStride) + column, ((row + 1) * BufferStride) + column);
+                    }
+                }
+            }
+            else if (Vector128.IsHardwareAccelerated)
+            {
+                Vector128<int> tap0Low = CreateTapVector128(ref taps, 0, 0);
+                Vector128<int> tap1Low = CreateTapVector128(ref taps, 1, 0);
+                Vector128<int> tap2Low = CreateTapVector128(ref taps, 2, 0);
+                Vector128<int> tap3Low = CreateTapVector128(ref taps, 3, 0);
+                Vector128<int> tap4Low = CreateTapVector128(ref taps, 4, 0);
+                Vector128<int> tap5Low = CreateTapVector128(ref taps, 5, 0);
+                Vector128<int> tap6Low = CreateTapVector128(ref taps, 6, 0);
+                Vector128<int> tap0High = CreateTapVector128(ref taps, 0, 4);
+                Vector128<int> tap1High = CreateTapVector128(ref taps, 1, 4);
+                Vector128<int> tap2High = CreateTapVector128(ref taps, 2, 4);
+                Vector128<int> tap3High = CreateTapVector128(ref taps, 3, 4);
+                Vector128<int> tap4High = CreateTapVector128(ref taps, 4, 4);
+                Vector128<int> tap5High = CreateTapVector128(ref taps, 5, 4);
+                Vector128<int> tap6High = CreateTapVector128(ref taps, 6, 4);
+                Vector128<int> rounding = Vector128.Create(8);
+                Vector128<int> maximumVector = Vector128.Create(maximum);
+
+                for (int row = 1; row <= height; row += 2)
+                {
+                    for (int column = 1; column <= width; column += 4)
+                    {
+                        int sourceOffset = ((row - 1) * BufferStride) + column - 1;
+                        int p0 = Unsafe.Add(ref bufferBase, sourceOffset);
+                        int p1 = Unsafe.Add(ref bufferBase, sourceOffset + 1);
+                        int p2 = Unsafe.Add(ref bufferBase, sourceOffset + 2);
+                        int p3 = Unsafe.Add(ref bufferBase, sourceOffset + 3);
+                        int p4 = Unsafe.Add(ref bufferBase, sourceOffset + 4);
+                        int p5 = Unsafe.Add(ref bufferBase, sourceOffset + BufferStride);
+                        int p6 = Unsafe.Add(ref bufferBase, sourceOffset + (2 * BufferStride));
+                        Vector128<int> low = Calculate(tap0Low, tap1Low, tap2Low, tap3Low, tap4Low, tap5Low, tap6Low, p0, p1, p2, p3, p4, p5, p6);
+                        Vector128<int> high = Calculate(tap0High, tap1High, tap2High, tap3High, tap4High, tap5High, tap6High, p0, p1, p2, p3, p4, p5, p6);
+                        low = Vector128.Clamp((low + rounding) >> 4, Vector128<int>.Zero, maximumVector);
+                        high = Vector128.Clamp((high + rounding) >> 4, Vector128<int>.Zero, maximumVector);
+                        StoreFourShorts(low, ref bufferBase, (row * BufferStride) + column);
+                        StoreFourShorts(high, ref bufferBase, ((row + 1) * BufferStride) + column);
+                    }
+                }
+            }
+            else
+            {
+                PredictGroupsScalar(buffer, width, height, maximum, ref taps);
+            }
+
+            CopyToDestination(buffer, destination, destinationStride, width, height);
+        }
+
+        /// <inheritdoc/>
+        public override void PredictScalar(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height, Span<byte> scratch)
+        {
+            Span<byte> buffer = scratch[..ScratchLength];
+            ref byte aboveBase = ref MemoryMarshal.GetReference(above);
+            ref sbyte taps = ref MemoryMarshal.GetReference(TOperator.Taps);
+            Initialize(buffer, above, left, width, height, Unsafe.Subtract(ref aboveBase, 1));
+            PredictGroupsScalar(buffer, width, height, 255, ref taps);
+            CopyToDestinationScalar(buffer, destination, destinationStride, width, height);
+        }
+
+        /// <inheritdoc/>
+        public override void PredictScalar(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height, int bitDepth, Span<short> scratch)
+        {
+            Span<short> buffer = scratch[..ScratchLength];
+            ref short aboveBase = ref MemoryMarshal.GetReference(above);
+            ref sbyte taps = ref MemoryMarshal.GetReference(TOperator.Taps);
+            Initialize(buffer, above, left, width, height, Unsafe.Subtract(ref aboveBase, 1));
+            PredictGroupsScalar(buffer, width, height, (1 << bitDepth) - 1, ref taps);
+            CopyToDestinationScalar(buffer, destination, destinationStride, width, height);
+        }
+
+        /// <summary>
+        /// Initializes an 8-bit recursive filter-intra workspace from the prepared top and left references.
+        /// </summary>
+        /// <param name="buffer">The recursive workspace.</param>
+        /// <param name="above">The top reference.</param>
+        /// <param name="left">The left reference.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        /// <param name="topLeft">The shared top-left reference.</param>
+        private static void Initialize(Span<byte> buffer, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height, byte topLeft)
+        {
+            buffer[0] = topLeft;
+            above[..width].CopyTo(buffer[1..]);
+            for (int row = 0; row < height; row++)
+            {
+                buffer[(row + 1) * BufferStride] = left[row];
+            }
+        }
+
+        /// <summary>
+        /// Initializes a high-bit-depth recursive filter-intra workspace from the prepared top and left references.
+        /// </summary>
+        /// <param name="buffer">The recursive workspace.</param>
+        /// <param name="above">The top reference.</param>
+        /// <param name="left">The left reference.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        /// <param name="topLeft">The shared top-left reference.</param>
+        private static void Initialize(Span<short> buffer, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height, short topLeft)
+        {
+            buffer[0] = topLeft;
+            above[..width].CopyTo(buffer[1..]);
+            for (int row = 0; row < height; row++)
+            {
+                buffer[(row + 1) * BufferStride] = left[row];
+            }
+        }
+
+        /// <summary>
+        /// Creates the coefficients for eight output samples at one tap position.
+        /// </summary>
+        /// <param name="taps">The first coefficient in the operator table.</param>
+        /// <param name="tap">The tap position.</param>
+        /// <returns>The coefficient vector.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector256<int> CreateTapVector256(ref sbyte taps, int tap)
+            => Vector256.Create(
+                (int)Unsafe.Add(ref taps, tap),
+                Unsafe.Add(ref taps, 7 + tap),
+                Unsafe.Add(ref taps, 14 + tap),
+                Unsafe.Add(ref taps, 21 + tap),
+                Unsafe.Add(ref taps, 28 + tap),
+                Unsafe.Add(ref taps, 35 + tap),
+                Unsafe.Add(ref taps, 42 + tap),
+                Unsafe.Add(ref taps, 49 + tap));
+
+        /// <summary>
+        /// Creates the coefficients for four output samples at one tap position.
+        /// </summary>
+        /// <param name="taps">The first coefficient in the operator table.</param>
+        /// <param name="tap">The tap position.</param>
+        /// <param name="pixel">The first output sample.</param>
+        /// <returns>The coefficient vector.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector128<int> CreateTapVector128(ref sbyte taps, int tap, int pixel)
+            => Vector128.Create(
+                (int)Unsafe.Add(ref taps, (pixel * 7) + tap),
+                Unsafe.Add(ref taps, ((pixel + 1) * 7) + tap),
+                Unsafe.Add(ref taps, ((pixel + 2) * 7) + tap),
+                Unsafe.Add(ref taps, ((pixel + 3) * 7) + tap));
+
+        /// <summary>
+        /// Calculates eight filtered predictions from seven reconstructed samples.
+        /// </summary>
+        /// <param name="tap0">The first tap coefficients.</param>
+        /// <param name="tap1">The second tap coefficients.</param>
+        /// <param name="tap2">The third tap coefficients.</param>
+        /// <param name="tap3">The fourth tap coefficients.</param>
+        /// <param name="tap4">The fifth tap coefficients.</param>
+        /// <param name="tap5">The sixth tap coefficients.</param>
+        /// <param name="tap6">The seventh tap coefficients.</param>
+        /// <param name="p0">The first reconstructed sample.</param>
+        /// <param name="p1">The second reconstructed sample.</param>
+        /// <param name="p2">The third reconstructed sample.</param>
+        /// <param name="p3">The fourth reconstructed sample.</param>
+        /// <param name="p4">The fifth reconstructed sample.</param>
+        /// <param name="p5">The sixth reconstructed sample.</param>
+        /// <param name="p6">The seventh reconstructed sample.</param>
+        /// <returns>The unrounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector256<int> Calculate(
+            Vector256<int> tap0,
+            Vector256<int> tap1,
+            Vector256<int> tap2,
+            Vector256<int> tap3,
+            Vector256<int> tap4,
+            Vector256<int> tap5,
+            Vector256<int> tap6,
+            int p0,
+            int p1,
+            int p2,
+            int p3,
+            int p4,
+            int p5,
+            int p6)
+            => (tap0 * p0) + (tap1 * p1) + (tap2 * p2) + (tap3 * p3) + (tap4 * p4) + (tap5 * p5) + (tap6 * p6);
+
+        /// <summary>
+        /// Calculates four filtered predictions from seven reconstructed samples.
+        /// </summary>
+        /// <param name="tap0">The first tap coefficients.</param>
+        /// <param name="tap1">The second tap coefficients.</param>
+        /// <param name="tap2">The third tap coefficients.</param>
+        /// <param name="tap3">The fourth tap coefficients.</param>
+        /// <param name="tap4">The fifth tap coefficients.</param>
+        /// <param name="tap5">The sixth tap coefficients.</param>
+        /// <param name="tap6">The seventh tap coefficients.</param>
+        /// <param name="p0">The first reconstructed sample.</param>
+        /// <param name="p1">The second reconstructed sample.</param>
+        /// <param name="p2">The third reconstructed sample.</param>
+        /// <param name="p3">The fourth reconstructed sample.</param>
+        /// <param name="p4">The fifth reconstructed sample.</param>
+        /// <param name="p5">The sixth reconstructed sample.</param>
+        /// <param name="p6">The seventh reconstructed sample.</param>
+        /// <returns>The unrounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector128<int> Calculate(
+            Vector128<int> tap0,
+            Vector128<int> tap1,
+            Vector128<int> tap2,
+            Vector128<int> tap3,
+            Vector128<int> tap4,
+            Vector128<int> tap5,
+            Vector128<int> tap6,
+            int p0,
+            int p1,
+            int p2,
+            int p3,
+            int p4,
+            int p5,
+            int p6)
+            => (tap0 * p0) + (tap1 * p1) + (tap2 * p2) + (tap3 * p3) + (tap4 * p4) + (tap5 * p5) + (tap6 * p6);
+
+        /// <summary>
+        /// Stores eight 8-bit predictions into the two recursive output rows.
+        /// </summary>
+        /// <param name="prediction">The clamped predictions.</param>
+        /// <param name="buffer">The recursive workspace origin.</param>
+        /// <param name="firstRowOffset">The first output-row offset.</param>
+        /// <param name="secondRowOffset">The second output-row offset.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void StoreEightBytes(Vector256<int> prediction, ref byte buffer, int firstRowOffset, int secondRowOffset)
+        {
+            Vector256<ushort> narrowed16 = Vector256.Narrow(prediction.AsUInt32(), Vector256<uint>.Zero);
+            Vector256<byte> narrowed8 = Vector256.Narrow(narrowed16, Vector256<ushort>.Zero);
+            Unsafe.As<byte, uint>(ref Unsafe.Add(ref buffer, firstRowOffset)) = narrowed8.AsUInt32().GetElement(0);
+            Unsafe.As<byte, uint>(ref Unsafe.Add(ref buffer, secondRowOffset)) = narrowed8.AsUInt32().GetElement(1);
+        }
+
+        /// <summary>
+        /// Stores four 8-bit predictions into one recursive output row.
+        /// </summary>
+        /// <param name="prediction">The clamped predictions.</param>
+        /// <param name="buffer">The recursive workspace origin.</param>
+        /// <param name="offset">The output-row offset.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void StoreFourBytes(Vector128<int> prediction, ref byte buffer, int offset)
+        {
+            Vector128<ushort> narrowed16 = Vector128.Narrow(prediction.AsUInt32(), Vector128<uint>.Zero);
+            Vector128<byte> narrowed8 = Vector128.Narrow(narrowed16, Vector128<ushort>.Zero);
+            Unsafe.As<byte, uint>(ref Unsafe.Add(ref buffer, offset)) = narrowed8.AsUInt32().GetElement(0);
+        }
+
+        /// <summary>
+        /// Stores eight high-bit-depth predictions into the two recursive output rows.
+        /// </summary>
+        /// <param name="prediction">The clamped predictions.</param>
+        /// <param name="buffer">The recursive workspace origin.</param>
+        /// <param name="firstRowOffset">The first output-row offset.</param>
+        /// <param name="secondRowOffset">The second output-row offset.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void StoreEightShorts(Vector256<int> prediction, ref short buffer, int firstRowOffset, int secondRowOffset)
+        {
+            Vector256<short> narrowed = Vector256.Narrow(prediction, Vector256<int>.Zero);
+            Unsafe.As<short, ulong>(ref Unsafe.Add(ref buffer, firstRowOffset)) = narrowed.AsUInt64().GetElement(0);
+            Unsafe.As<short, ulong>(ref Unsafe.Add(ref buffer, secondRowOffset)) = narrowed.AsUInt64().GetElement(1);
+        }
+
+        /// <summary>
+        /// Stores four high-bit-depth predictions into one recursive output row.
+        /// </summary>
+        /// <param name="prediction">The clamped predictions.</param>
+        /// <param name="buffer">The recursive workspace origin.</param>
+        /// <param name="offset">The output-row offset.</param>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static void StoreFourShorts(Vector128<int> prediction, ref short buffer, int offset)
+        {
+            Vector128<short> narrowed = Vector128.Narrow(prediction, Vector128<int>.Zero);
+            Unsafe.As<short, ulong>(ref Unsafe.Add(ref buffer, offset)) = narrowed.AsUInt64().GetElement(0);
+        }
+
+        /// <summary>
+        /// Calculates every 8-bit recursive filter group without hardware intrinsics.
+        /// </summary>
+        /// <param name="buffer">The initialized recursive workspace.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        /// <param name="maximum">The maximum reconstructed sample.</param>
+        /// <param name="taps">The first filter coefficient.</param>
+        private static void PredictGroupsScalar(Span<byte> buffer, int width, int height, int maximum, ref sbyte taps)
+        {
+            ref byte bufferBase = ref MemoryMarshal.GetReference(buffer);
+            for (int row = 1; row <= height; row += 2)
+            {
+                for (int column = 1; column <= width; column += 4)
+                {
+                    int sourceOffset = ((row - 1) * BufferStride) + column - 1;
+                    int p0 = Unsafe.Add(ref bufferBase, sourceOffset);
+                    int p1 = Unsafe.Add(ref bufferBase, sourceOffset + 1);
+                    int p2 = Unsafe.Add(ref bufferBase, sourceOffset + 2);
+                    int p3 = Unsafe.Add(ref bufferBase, sourceOffset + 3);
+                    int p4 = Unsafe.Add(ref bufferBase, sourceOffset + 4);
+                    int p5 = Unsafe.Add(ref bufferBase, sourceOffset + BufferStride);
+                    int p6 = Unsafe.Add(ref bufferBase, sourceOffset + (2 * BufferStride));
+                    for (int pixel = 0; pixel < 8; pixel++)
+                    {
+                        int tapOffset = pixel * 7;
+                        int prediction =
+                            (Unsafe.Add(ref taps, tapOffset) * p0)
+                            + (Unsafe.Add(ref taps, tapOffset + 1) * p1)
+                            + (Unsafe.Add(ref taps, tapOffset + 2) * p2)
+                            + (Unsafe.Add(ref taps, tapOffset + 3) * p3)
+                            + (Unsafe.Add(ref taps, tapOffset + 4) * p4)
+                            + (Unsafe.Add(ref taps, tapOffset + 5) * p5)
+                            + (Unsafe.Add(ref taps, tapOffset + 6) * p6);
+
+                        int destinationOffset = ((row + (pixel >> 2)) * BufferStride) + column + (pixel & 3);
+                        Unsafe.Add(ref bufferBase, destinationOffset) = (byte)Math.Clamp((prediction + 8) >> 4, 0, maximum);
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Calculates every high-bit-depth recursive filter group without hardware intrinsics.
+        /// </summary>
+        /// <param name="buffer">The initialized recursive workspace.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        /// <param name="maximum">The maximum reconstructed sample.</param>
+        /// <param name="taps">The first filter coefficient.</param>
+        private static void PredictGroupsScalar(Span<short> buffer, int width, int height, int maximum, ref sbyte taps)
+        {
+            ref short bufferBase = ref MemoryMarshal.GetReference(buffer);
+            for (int row = 1; row <= height; row += 2)
+            {
+                for (int column = 1; column <= width; column += 4)
+                {
+                    int sourceOffset = ((row - 1) * BufferStride) + column - 1;
+                    int p0 = Unsafe.Add(ref bufferBase, sourceOffset);
+                    int p1 = Unsafe.Add(ref bufferBase, sourceOffset + 1);
+                    int p2 = Unsafe.Add(ref bufferBase, sourceOffset + 2);
+                    int p3 = Unsafe.Add(ref bufferBase, sourceOffset + 3);
+                    int p4 = Unsafe.Add(ref bufferBase, sourceOffset + 4);
+                    int p5 = Unsafe.Add(ref bufferBase, sourceOffset + BufferStride);
+                    int p6 = Unsafe.Add(ref bufferBase, sourceOffset + (2 * BufferStride));
+                    for (int pixel = 0; pixel < 8; pixel++)
+                    {
+                        int tapOffset = pixel * 7;
+                        int prediction =
+                            (Unsafe.Add(ref taps, tapOffset) * p0)
+                            + (Unsafe.Add(ref taps, tapOffset + 1) * p1)
+                            + (Unsafe.Add(ref taps, tapOffset + 2) * p2)
+                            + (Unsafe.Add(ref taps, tapOffset + 3) * p3)
+                            + (Unsafe.Add(ref taps, tapOffset + 4) * p4)
+                            + (Unsafe.Add(ref taps, tapOffset + 5) * p5)
+                            + (Unsafe.Add(ref taps, tapOffset + 6) * p6);
+
+                        int destinationOffset = ((row + (pixel >> 2)) * BufferStride) + column + (pixel & 3);
+                        Unsafe.Add(ref bufferBase, destinationOffset) = (short)Math.Clamp((prediction + 8) >> 4, 0, maximum);
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copies an 8-bit recursive workspace into the strided destination.
+        /// </summary>
+        /// <param name="buffer">The completed recursive workspace.</param>
+        /// <param name="destination">The destination block origin.</param>
+        /// <param name="destinationStride">The destination row stride.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        private static void CopyToDestination(ReadOnlySpan<byte> buffer, Span<byte> destination, int destinationStride, int width, int height)
+        {
+            for (int row = 0; row < height; row++)
+            {
+                buffer.Slice(((row + 1) * BufferStride) + 1, width).CopyTo(destination.Slice(row * destinationStride, width));
+            }
+        }
+
+        /// <summary>
+        /// Copies a high-bit-depth recursive workspace into the strided destination.
+        /// </summary>
+        /// <param name="buffer">The completed recursive workspace.</param>
+        /// <param name="destination">The destination block origin.</param>
+        /// <param name="destinationStride">The destination row stride.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        private static void CopyToDestination(ReadOnlySpan<short> buffer, Span<short> destination, int destinationStride, int width, int height)
+        {
+            for (int row = 0; row < height; row++)
+            {
+                buffer.Slice(((row + 1) * BufferStride) + 1, width).CopyTo(destination.Slice(row * destinationStride, width));
+            }
+        }
+
+        /// <summary>
+        /// Copies an 8-bit recursive workspace into the strided destination without vectorized span copying.
+        /// </summary>
+        /// <param name="buffer">The completed recursive workspace.</param>
+        /// <param name="destination">The destination block origin.</param>
+        /// <param name="destinationStride">The destination row stride.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        private static void CopyToDestinationScalar(ReadOnlySpan<byte> buffer, Span<byte> destination, int destinationStride, int width, int height)
+        {
+            for (int row = 0; row < height; row++)
+            {
+                int sourceOffset = ((row + 1) * BufferStride) + 1;
+                int destinationOffset = row * destinationStride;
+                for (int column = 0; column < width; column++)
+                {
+                    destination[destinationOffset + column] = buffer[sourceOffset + column];
+                }
+            }
+        }
+
+        /// <summary>
+        /// Copies a high-bit-depth recursive workspace into the strided destination without vectorized span copying.
+        /// </summary>
+        /// <param name="buffer">The completed recursive workspace.</param>
+        /// <param name="destination">The destination block origin.</param>
+        /// <param name="destinationStride">The destination row stride.</param>
+        /// <param name="width">The block width.</param>
+        /// <param name="height">The block height.</param>
+        private static void CopyToDestinationScalar(ReadOnlySpan<short> buffer, Span<short> destination, int destinationStride, int width, int height)
+        {
+            for (int row = 0; row < height; row++)
+            {
+                int sourceOffset = ((row + 1) * BufferStride) + 1;
+                int destinationOffset = row * destinationStride;
+                for (int column = 0; column < width; column++)
+                {
+                    destination[destinationOffset + column] = buffer[sourceOffset + column];
+                }
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.OperatorContract.cs

@@ -0,0 +1,25 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// Defines the coefficient set for one AV1 filter-intra prediction mode.
+    /// </summary>
+    internal interface IAv1FilterIntraPredictionOperator
+    {
+        /// <summary>
+        /// Gets the filter-intra mode implemented by the operator.
+        /// </summary>
+        public static abstract Av1FilterIntraMode Mode { get; }
+
+        /// <summary>
+        /// Gets the eight seven-tap coefficient rows used by the operator.
+        /// </summary>
+        public static abstract ReadOnlySpan<sbyte> Taps { get; }
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.PaethOperator.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// Defines the AV1 Paeth filter-intra coefficient operator.
+    /// </summary>
+    internal readonly struct PaethOperator : IAv1FilterIntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1FilterIntraMode Mode => Av1FilterIntraMode.Paeth;
+
+        /// <inheritdoc/>
+        public static ReadOnlySpan<sbyte> Taps =>
+        [
+            -12, 14, 0, 0, 0, 14, 0,
+        -10, 0, 14, 0, 0, 12, 0,
+        -9, 0, 0, 14, 0, 11, 0,
+        -8, 0, 0, 0, 14, 10, 0,
+        -10, 12, 0, 0, 0, 0, 14,
+        -9, 1, 12, 0, 0, 0, 12,
+        -8, 0, 0, 12, 0, 1, 11,
+        -7, 0, 0, 1, 12, 1, 9,
+    ];
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.VerticalOperator.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// Defines the AV1 vertical filter-intra coefficient operator.
+    /// </summary>
+    internal readonly struct VerticalOperator : IAv1FilterIntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1FilterIntraMode Mode => Av1FilterIntraMode.Vertical;
+
+        /// <inheritdoc/>
+        public static ReadOnlySpan<sbyte> Taps =>
+        [
+            -10, 16, 0, 0, 0, 10, 0,
+        -6, 0, 16, 0, 0, 6, 0,
+        -4, 0, 0, 16, 0, 4, 0,
+        -2, 0, 0, 0, 16, 2, 0,
+        -10, 16, 0, 0, 0, 0, 10,
+        -6, 0, 16, 0, 0, 0, 6,
+        -4, 0, 0, 16, 0, 0, 4,
+        -2, 0, 0, 0, 16, 0, 2,
+    ];
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictor.cs

@@ -1,191 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using System.Runtime.InteropServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Produces AV1 filter intra predictions from reconstructed neighboring samples.
-/// </summary>
-/// <remarks>
-/// The scalar prediction follows the filter intra prediction process in section 7.11.2.3 of the AV1 specification.
-/// </remarks>
-internal static class Av1FilterIntraPredictor
-{
-    /// <summary>
-    /// The row stride of the temporary prediction buffer.
-    /// </summary>
-    private const int BufferStride = 33;
-
-    /// <summary>
-    /// The number of samples in the temporary prediction buffer.
-    /// </summary>
-    private const int BufferLength = BufferStride * BufferStride;
-
-    /// <summary>
-    /// The number of nonzero filter coefficients used to predict each sample.
-    /// </summary>
-    private const int TapsPerPixel = 7;
-
-    /// <summary>
-    /// The number of samples produced by each filter coefficient group.
-    /// </summary>
-    private const int PixelsPerGroup = 8;
-
-    /// <summary>
-    /// The number of stored coefficients for each filter intra mode.
-    /// </summary>
-    private const int TapsPerMode = TapsPerPixel * PixelsPerGroup;
-
-    /// <summary>
-    /// Gets the filter coefficients for the five AV1 filter intra modes.
-    /// </summary>
-    /// <remarks>
-    /// AV1 defines eight filters per mode over seven nonzero neighboring samples. The eighth coefficient used by
-    /// libaom is always zero, so it is omitted here to keep the scalar coefficient layout aligned with the work performed.
-    /// </remarks>
-    public static readonly sbyte[] Taps =
-    [
-
-        // DC
-        -6, 10, 0, 0, 0, 12, 0,
-        -5, 2, 10, 0, 0, 9, 0,
-        -3, 1, 1, 10, 0, 7, 0,
-        -3, 1, 1, 2, 10, 5, 0,
-        -4, 6, 0, 0, 0, 2, 12,
-        -3, 2, 6, 0, 0, 2, 9,
-        -3, 2, 2, 6, 0, 2, 7,
-        -3, 1, 2, 2, 6, 3, 5,
-
-        // Vertical
-        -10, 16, 0, 0, 0, 10, 0,
-        -6, 0, 16, 0, 0, 6, 0,
-        -4, 0, 0, 16, 0, 4, 0,
-        -2, 0, 0, 0, 16, 2, 0,
-        -10, 16, 0, 0, 0, 0, 10,
-        -6, 0, 16, 0, 0, 0, 6,
-        -4, 0, 0, 16, 0, 0, 4,
-        -2, 0, 0, 0, 16, 0, 2,
-
-        // Horizontal
-        -8, 8, 0, 0, 0, 16, 0,
-        -8, 0, 8, 0, 0, 16, 0,
-        -8, 0, 0, 8, 0, 16, 0,
-        -8, 0, 0, 0, 8, 16, 0,
-        -4, 4, 0, 0, 0, 0, 16,
-        -4, 0, 4, 0, 0, 0, 16,
-        -4, 0, 0, 4, 0, 0, 16,
-        -4, 0, 0, 0, 4, 0, 16,
-
-        // Directional 157 degrees
-        -2, 8, 0, 0, 0, 10, 0,
-        -1, 3, 8, 0, 0, 6, 0,
-        -1, 2, 3, 8, 0, 4, 0,
-        0, 1, 2, 3, 8, 2, 0,
-        -1, 4, 0, 0, 0, 3, 10,
-        -1, 3, 4, 0, 0, 4, 6,
-        -1, 2, 3, 4, 0, 4, 4,
-        -1, 2, 2, 3, 4, 3, 3,
-
-        // Paeth
-        -12, 14, 0, 0, 0, 14, 0,
-        -10, 0, 14, 0, 0, 12, 0,
-        -9, 0, 0, 14, 0, 11, 0,
-        -8, 0, 0, 0, 14, 10, 0,
-        -10, 12, 0, 0, 0, 0, 14,
-        -9, 1, 12, 0, 0, 0, 12,
-        -8, 0, 0, 12, 0, 1, 11,
-        -7, 0, 0, 1, 12, 1, 9,
-    ];
-
-    /// <summary>
-    /// Produces an 8-bit filter intra prediction for a transform block.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="mode">The filter intra mode whose coefficient set is applied.</param>
-    public static void Predict(
-        Span<byte> destination,
-        nuint destinationStride,
-        Av1TransformSize transformSize,
-        Span<byte> above,
-        Span<byte> left,
-        Av1FilterIntraMode mode)
-    {
-        int width = transformSize.GetWidth();
-        int height = transformSize.GetHeight();
-        DebugGuard.MustBeLessThanOrEqualTo(width, 32, nameof(width));
-        DebugGuard.MustBeLessThanOrEqualTo(height, 32, nameof(height));
-        Guard.MustBeGreaterThanOrEqualTo(destinationStride, (nuint)width, nameof(destinationStride));
-        Guard.MustBeSizedAtLeast(destination, (int)destinationStride * height, nameof(destination));
-        Guard.MustBeSizedAtLeast(above, width, nameof(above));
-        Guard.MustBeSizedAtLeast(left, height, nameof(left));
-
-        Span<byte> buffer = stackalloc byte[BufferLength];
-        ref byte bufferRef = ref buffer[0];
-        ref byte aboveRef = ref above[0];
-        ref byte leftRef = ref left[0];
-
-        // Row zero includes the top-left sample followed by the top neighbors.
-        // Column zero stores the left neighbors so each 4-by-2 group can consume the
-        // seven already-reconstructed samples defined by the recursive AV1 process.
-        bufferRef = Unsafe.Subtract(ref aboveRef, 1);
-        above[..width].CopyTo(buffer[1..]);
-        for (int row = 0; row < height; row++)
-        {
-            Unsafe.Add(ref bufferRef, (row + 1) * BufferStride) = Unsafe.Add(ref leftRef, row);
-        }
-
-        int modeOffset = (int)mode * TapsPerMode;
-        ref sbyte tapsRef = ref Taps[modeOffset];
-        for (int row = 1; row <= height; row += 2)
-        {
-            for (int column = 1; column <= width; column += 4)
-            {
-                int sourceOffset = ((row - 1) * BufferStride) + column - 1;
-                int p0 = Unsafe.Add(ref bufferRef, sourceOffset);
-                int p1 = Unsafe.Add(ref bufferRef, sourceOffset + 1);
-                int p2 = Unsafe.Add(ref bufferRef, sourceOffset + 2);
-                int p3 = Unsafe.Add(ref bufferRef, sourceOffset + 3);
-                int p4 = Unsafe.Add(ref bufferRef, sourceOffset + 4);
-                int p5 = Unsafe.Add(ref bufferRef, sourceOffset + BufferStride);
-                int p6 = Unsafe.Add(ref bufferRef, sourceOffset + (2 * BufferStride));
-
-                for (int pixel = 0; pixel < PixelsPerGroup; pixel++)
-                {
-                    int tapOffset = pixel * TapsPerPixel;
-                    int prediction =
-                        (Unsafe.Add(ref tapsRef, tapOffset) * p0)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 1) * p1)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 2) * p2)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 3) * p3)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 4) * p4)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 5) * p5)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 6) * p6);
-
-                    int rowOffset = pixel >> 2;
-                    int columnOffset = pixel & 3;
-                    int destinationOffset = ((row + rowOffset) * BufferStride) + column + columnOffset;
-                    Unsafe.Add(ref bufferRef, destinationOffset) =
-                        (byte)Av1Math.Clamp(Av1Math.RoundPowerOf2(prediction, 4), 0, 255);
-                }
-            }
-        }
-
-        ref byte destinationRef = ref destination[0];
-        for (int row = 0; row < height; row++)
-        {
-            buffer.Slice(((row + 1) * BufferStride) + 1, width).CopyTo(
-                MemoryMarshal.CreateSpan(ref destinationRef, width));
-
-            destinationRef = ref Unsafe.Add(ref destinationRef, destinationStride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1FilterIntraPredictorBase.cs

@@ -0,0 +1,121 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+/// <summary>
+/// Reconstructs AV1 filter-intra prediction blocks from prepared neighboring samples.
+/// </summary>
+/// <remarks>
+/// The implementation follows the recursive filter-intra process in section 7.11.2.3 of the AV1 specification.
+/// </remarks>
+internal abstract partial class Av1FilterIntraPredictorBase
+{
+    /// <summary>
+    /// The row stride of the recursive prediction workspace.
+    /// </summary>
+    public const int BufferStride = 33;
+
+    /// <summary>
+    /// The number of samples in the recursive prediction workspace.
+    /// </summary>
+    public const int ScratchLength = BufferStride * BufferStride;
+
+    /// <summary>
+    /// The DC filter-intra predictor.
+    /// </summary>
+    private static readonly Av1FilterIntraPredictor<DcOperator> DcPredictor = new();
+
+    /// <summary>
+    /// The vertical filter-intra predictor.
+    /// </summary>
+    private static readonly Av1FilterIntraPredictor<VerticalOperator> VerticalPredictor = new();
+
+    /// <summary>
+    /// The horizontal filter-intra predictor.
+    /// </summary>
+    private static readonly Av1FilterIntraPredictor<HorizontalOperator> HorizontalPredictor = new();
+
+    /// <summary>
+    /// The 157-degree directional filter-intra predictor.
+    /// </summary>
+    private static readonly Av1FilterIntraPredictor<Directional157Operator> Directional157Predictor = new();
+
+    /// <summary>
+    /// The Paeth filter-intra predictor.
+    /// </summary>
+    private static readonly Av1FilterIntraPredictor<PaethOperator> PaethPredictor = new();
+
+    /// <summary>
+    /// Gets the filter-intra mode implemented by this predictor.
+    /// </summary>
+    public abstract Av1FilterIntraMode Mode { get; }
+
+    /// <summary>
+    /// Gets the closed predictor for a filter-intra mode.
+    /// </summary>
+    /// <param name="mode">The decoded filter-intra mode.</param>
+    /// <returns>The predictor for <paramref name="mode"/>.</returns>
+    public static Av1FilterIntraPredictorBase GetPredictor(Av1FilterIntraMode mode)
+        => mode switch
+        {
+            Av1FilterIntraMode.DC => DcPredictor,
+            Av1FilterIntraMode.Vertical => VerticalPredictor,
+            Av1FilterIntraMode.Horizontal => HorizontalPredictor,
+            Av1FilterIntraMode.Directional157 => Directional157Predictor,
+            Av1FilterIntraMode.Paeth => PaethPredictor,
+            _ => throw new InvalidImageContentException($"Filter-intra mode {mode} is not defined by AV1."),
+        };
+
+    /// <summary>
+    /// Predicts an 8-bit filter-intra block.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    /// <param name="scratch">The caller-owned recursive prediction workspace.</param>
+    public abstract void Predict(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height, Span<byte> scratch);
+
+    /// <summary>
+    /// Predicts a high-bit-depth filter-intra block.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    /// <param name="bitDepth">The reconstructed sample precision.</param>
+    /// <param name="scratch">The caller-owned recursive prediction workspace.</param>
+    public abstract void Predict(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height, int bitDepth, Span<short> scratch);
+
+    /// <summary>
+    /// Predicts an 8-bit filter-intra block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    /// <param name="scratch">The caller-owned recursive prediction workspace.</param>
+    public abstract void PredictScalar(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height, Span<byte> scratch);
+
+    /// <summary>
+    /// Predicts a high-bit-depth filter-intra block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width.</param>
+    /// <param name="height">The block height.</param>
+    /// <param name="bitDepth">The reconstructed sample precision.</param>
+    /// <param name="scratch">The caller-owned recursive prediction workspace.</param>
+    public abstract void PredictScalar(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height, int bitDepth, Span<short> scratch);
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1HighBitDepthPredictor.cs

@@ -1,602 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Implements AV1 intra prediction for 10-bit and 12-bit sample buffers.
-/// </summary>
-/// <remarks>
-/// Samples are stored in signed 16-bit buffers, but predictions are clamped to the nonnegative range of the signaled bit depth.
-/// </remarks>
-internal static class Av1HighBitDepthPredictor
-{
-    /// <summary>
-    /// The row stride of the temporary filter intra prediction buffer.
-    /// </summary>
-    private const int FilterBufferStride = 33;
-
-    /// <summary>
-    /// The number of samples in the temporary filter intra prediction buffer.
-    /// </summary>
-    private const int FilterBufferLength = FilterBufferStride * FilterBufferStride;
-
-    /// <summary>
-    /// The number of nonzero filter coefficients used to predict each filter intra sample.
-    /// </summary>
-    private const int FilterTapsPerPixel = 7;
-
-    /// <summary>
-    /// The number of samples produced by each filter coefficient group.
-    /// </summary>
-    private const int FilterPixelsPerGroup = 8;
-
-    /// <summary>
-    /// The number of stored coefficients for each filter intra mode.
-    /// </summary>
-    private const int FilterTapsPerMode = FilterTapsPerPixel * FilterPixelsPerGroup;
-
-    /// <summary>
-    /// Produces a high-bit-depth DC intra prediction from the available neighboring samples.
-    /// </summary>
-    /// <param name="hasLeft">A value indicating whether reconstructed left samples are available.</param>
-    /// <param name="hasAbove">A value indicating whether reconstructed top samples are available.</param>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="bitDepth">The number of bits used to represent each sample.</param>
-    public static void DcPredictor(
-        bool hasLeft,
-        bool hasAbove,
-        Av1TransformSize transformSize,
-        Span<short> destination,
-        nuint destinationStride,
-        Span<short> above,
-        Span<short> left,
-        int bitDepth)
-    {
-        int width = transformSize.GetWidth();
-        int height = transformSize.GetHeight();
-        int sum = 0;
-        int count = 0;
-
-        if (hasAbove)
-        {
-            for (int column = 0; column < width; column++)
-            {
-                sum += above[column];
-            }
-
-            count += width;
-        }
-
-        if (hasLeft)
-        {
-            for (int row = 0; row < height; row++)
-            {
-                sum += left[row];
-            }
-
-            count += height;
-        }
-
-        short prediction = count == 0
-            ? (short)(1 << (bitDepth - 1))
-            : (short)((sum + (count >> 1)) / count);
-
-        // The midpoint is normative when neither edge exists; otherwise the half-count bias
-        // rounds the mean of the available top and left samples to the nearest integer.
-        Fill(destination, destinationStride, width, height, prediction);
-    }
-
-    /// <summary>
-    /// Produces a high-bit-depth nondirectional intra prediction.
-    /// </summary>
-    /// <param name="mode">The nondirectional prediction mode to apply.</param>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    public static void GeneralPredictor(
-        Av1PredictionMode mode,
-        Av1TransformSize transformSize,
-        Span<short> destination,
-        nuint destinationStride,
-        Span<short> above,
-        Span<short> left)
-    {
-        int width = transformSize.GetWidth();
-        int height = transformSize.GetHeight();
-
-        switch (mode)
-        {
-            case Av1PredictionMode.Horizontal:
-                PredictHorizontal(destination, destinationStride, left, width, height);
-                break;
-            case Av1PredictionMode.Vertical:
-                PredictVertical(destination, destinationStride, above, width, height);
-                break;
-            case Av1PredictionMode.Paeth:
-                PredictPaeth(destination, destinationStride, above, left, width, height);
-                break;
-            case Av1PredictionMode.Smooth:
-                PredictSmooth(destination, destinationStride, above, left, width, height);
-                break;
-            case Av1PredictionMode.SmoothHorizontal:
-                PredictSmoothHorizontal(destination, destinationStride, above, left, width, height);
-                break;
-            case Av1PredictionMode.SmoothVertical:
-                PredictSmoothVertical(destination, destinationStride, above, left, width, height);
-                break;
-        }
-    }
-
-    /// <summary>
-    /// Produces a high-bit-depth directional intra prediction.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="above">The top reference samples, including any required extension.</param>
-    /// <param name="left">The left reference samples, including any required extension.</param>
-    /// <param name="upsampleAbove">A value indicating whether the top reference samples were upsampled.</param>
-    /// <param name="upsampleLeft">A value indicating whether the left reference samples were upsampled.</param>
-    /// <param name="angle">The prediction angle in degrees.</param>
-    /// <param name="bitDepth">The number of bits used to represent each sample.</param>
-    public static void DirectionalPredictor(
-        Span<short> destination,
-        nuint destinationStride,
-        Av1TransformSize transformSize,
-        Span<short> above,
-        Span<short> left,
-        bool upsampleAbove,
-        bool upsampleLeft,
-        int angle,
-        int bitDepth)
-    {
-        Guard.MustBeBetweenOrEqualTo(angle, 1, 269, nameof(angle));
-        int dx = Av1PredictorFactory.GetDeltaX(angle);
-        int dy = Av1PredictorFactory.GetDeltaY(angle);
-        int width = transformSize.GetWidth();
-        int height = transformSize.GetHeight();
-
-        // Angles on a cardinal axis copy one reference edge directly. Other angles are
-        // separated into the three AV1 projection zones according to the edges they cross.
-        if (angle is > 0 and < 90)
-        {
-            PredictDirectionalZone1(destination, destinationStride, above, upsampleAbove, dx, width, height, bitDepth);
-        }
-        else if (angle is > 90 and < 180)
-        {
-            PredictDirectionalZone2(destination, destinationStride, above, left, upsampleAbove, upsampleLeft, dx, dy, width, height, bitDepth);
-        }
-        else if (angle is > 180 and < 270)
-        {
-            PredictDirectionalZone3(destination, destinationStride, left, upsampleLeft, dx, dy, width, height, bitDepth);
-        }
-        else if (angle == 90)
-        {
-            PredictVertical(destination, destinationStride, above, width, height);
-        }
-        else if (angle == 180)
-        {
-            PredictHorizontal(destination, destinationStride, left, width, height);
-        }
-    }
-
-    /// <summary>
-    /// Produces a high-bit-depth filter intra prediction.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="transformSize">The transform size that determines the prediction block dimensions.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="mode">The filter intra mode whose coefficient set is applied.</param>
-    /// <param name="bitDepth">The number of bits used to represent each sample.</param>
-    public static void FilterIntraPredictor(
-        Span<short> destination,
-        nuint destinationStride,
-        Av1TransformSize transformSize,
-        Span<short> above,
-        Span<short> left,
-        Av1FilterIntraMode mode,
-        int bitDepth)
-    {
-        int width = transformSize.GetWidth();
-        int height = transformSize.GetHeight();
-        int maximum = (1 << bitDepth) - 1;
-        DebugGuard.MustBeLessThanOrEqualTo(width, 32, nameof(width));
-        DebugGuard.MustBeLessThanOrEqualTo(height, 32, nameof(height));
-        Guard.MustBeGreaterThanOrEqualTo(destinationStride, (nuint)width, nameof(destinationStride));
-        Guard.MustBeSizedAtLeast(destination, (int)destinationStride * height, nameof(destination));
-        Guard.MustBeSizedAtLeast(above, width, nameof(above));
-        Guard.MustBeSizedAtLeast(left, height, nameof(left));
-
-        Span<short> buffer = stackalloc short[FilterBufferLength];
-        ref short bufferRef = ref buffer[0];
-        ref short aboveRef = ref above[0];
-        ref short leftRef = ref left[0];
-
-        // Row zero includes the top-left sample followed by the top neighbors.
-        // Column zero stores the left neighbors so each 4-by-2 group can consume the
-        // seven already-reconstructed samples defined by the recursive AV1 process.
-        bufferRef = Unsafe.Subtract(ref aboveRef, 1);
-        above[..width].CopyTo(buffer[1..]);
-        for (int row = 0; row < height; row++)
-        {
-            Unsafe.Add(ref bufferRef, (row + 1) * FilterBufferStride) = Unsafe.Add(ref leftRef, row);
-        }
-
-        int modeOffset = (int)mode * FilterTapsPerMode;
-        ref sbyte tapsRef = ref Av1FilterIntraPredictor.Taps[modeOffset];
-        for (int row = 1; row <= height; row += 2)
-        {
-            for (int column = 1; column <= width; column += 4)
-            {
-                int sourceOffset = ((row - 1) * FilterBufferStride) + column - 1;
-                int p0 = Unsafe.Add(ref bufferRef, sourceOffset);
-                int p1 = Unsafe.Add(ref bufferRef, sourceOffset + 1);
-                int p2 = Unsafe.Add(ref bufferRef, sourceOffset + 2);
-                int p3 = Unsafe.Add(ref bufferRef, sourceOffset + 3);
-                int p4 = Unsafe.Add(ref bufferRef, sourceOffset + 4);
-                int p5 = Unsafe.Add(ref bufferRef, sourceOffset + FilterBufferStride);
-                int p6 = Unsafe.Add(ref bufferRef, sourceOffset + (2 * FilterBufferStride));
-
-                for (int pixel = 0; pixel < FilterPixelsPerGroup; pixel++)
-                {
-                    int tapOffset = pixel * FilterTapsPerPixel;
-                    int prediction =
-                        (Unsafe.Add(ref tapsRef, tapOffset) * p0)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 1) * p1)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 2) * p2)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 3) * p3)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 4) * p4)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 5) * p5)
-                        + (Unsafe.Add(ref tapsRef, tapOffset + 6) * p6);
-
-                    int rowOffset = pixel >> 2;
-                    int columnOffset = pixel & 3;
-                    int destinationOffset = ((row + rowOffset) * FilterBufferStride) + column + columnOffset;
-                    Unsafe.Add(ref bufferRef, destinationOffset) =
-                        (short)Av1Math.Clamp(Av1Math.RoundPowerOf2(prediction, 4), 0, maximum);
-                }
-            }
-        }
-
-        for (int row = 0; row < height; row++)
-        {
-            buffer.Slice(((row + 1) * FilterBufferStride) + 1, width).CopyTo(
-                destination.Slice(row * (int)destinationStride, width));
-        }
-    }
-
-    /// <summary>
-    /// Copies each left reference sample across one destination row.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    private static void PredictHorizontal(Span<short> destination, nuint stride, Span<short> left, int width, int height)
-    {
-        for (int row = 0; row < height; row++)
-        {
-            destination.Slice(row * (int)stride, width).Fill(left[row]);
-        }
-    }
-
-    /// <summary>
-    /// Copies the top reference samples into every destination row.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    private static void PredictVertical(Span<short> destination, nuint stride, Span<short> above, int width, int height)
-    {
-        for (int row = 0; row < height; row++)
-        {
-            above[..width].CopyTo(destination.Slice(row * (int)stride, width));
-        }
-    }
-
-    /// <summary>
-    /// Produces a Paeth prediction from the nearest top, left, and top-left reference sample.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    private static void PredictPaeth(Span<short> destination, nuint stride, Span<short> above, Span<short> left, int width, int height)
-    {
-        int topLeft = Unsafe.Subtract(ref above[0], 1);
-        for (int row = 0; row < height; row++)
-        {
-            Span<short> destinationRow = destination.Slice(row * (int)stride, width);
-            for (int column = 0; column < width; column++)
-            {
-                short leftValue = left[row];
-                short topValue = above[column];
-                int basis = topValue + leftValue - topLeft;
-                int leftDistance = Av1Math.AbsoluteDifference(basis, leftValue);
-                int topDistance = Av1Math.AbsoluteDifference(basis, topValue);
-                int topLeftDistance = Av1Math.AbsoluteDifference(basis, topLeft);
-
-                // The comparison order preserves AV1's left, top, then top-left tie precedence.
-                destinationRow[column] = leftDistance <= topDistance && leftDistance <= topLeftDistance
-                    ? leftValue
-                    : topDistance <= topLeftDistance ? topValue : (short)topLeft;
-            }
-        }
-    }
-
-    /// <summary>
-    /// Produces a two-dimensional smooth prediction from the four terminating edge samples.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    private static void PredictSmooth(Span<short> destination, nuint stride, Span<short> above, Span<short> left, int width, int height)
-    {
-        int below = left[height - 1];
-        int right = above[width - 1];
-        Span<int> widthWeights = Av1SmoothPredictor.Weights.AsSpan(width, width);
-        Span<int> heightWeights = Av1SmoothPredictor.Weights.AsSpan(height, height);
-        int scale = 1 << Av1SmoothPredictor.WeightLog2Scale;
-        int log2Scale = Av1SmoothPredictor.WeightLog2Scale + 1;
-
-        // Horizontal weights follow the block width and vertical weights follow the height.
-        // Keeping those domains separate is required for rectangular transform blocks.
-        for (int row = 0; row < height; row++)
-        {
-            int rowWeight = heightWeights[row];
-            Span<short> destinationRow = destination.Slice(row * (int)stride, width);
-            for (int column = 0; column < width; column++)
-            {
-                int columnWeight = widthWeights[column];
-                int prediction = (above[column] * rowWeight) + (below * (scale - rowWeight));
-                prediction += (left[row] * columnWeight) + (right * (scale - columnWeight));
-                destinationRow[column] = (short)Av1Math.DivideRound(prediction, log2Scale);
-            }
-        }
-    }
-
-    /// <summary>
-    /// Produces a horizontal smooth prediction between the left and right edge samples.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    private static void PredictSmoothHorizontal(Span<short> destination, nuint stride, Span<short> above, Span<short> left, int width, int height)
-    {
-        int right = above[width - 1];
-        Span<int> weights = Av1SmoothPredictor.Weights.AsSpan(width, width);
-        int scale = 1 << Av1SmoothPredictor.WeightLog2Scale;
-
-        for (int row = 0; row < height; row++)
-        {
-            Span<short> destinationRow = destination.Slice(row * (int)stride, width);
-            for (int column = 0; column < width; column++)
-            {
-                int weight = weights[column];
-                int prediction = (left[row] * weight) + (right * (scale - weight));
-                destinationRow[column] = (short)Av1Math.DivideRound(prediction, Av1SmoothPredictor.WeightLog2Scale);
-            }
-        }
-    }
-
-    /// <summary>
-    /// Produces a vertical smooth prediction between the top and bottom edge samples.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The reconstructed top reference samples.</param>
-    /// <param name="left">The reconstructed left reference samples.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    private static void PredictSmoothVertical(Span<short> destination, nuint stride, Span<short> above, Span<short> left, int width, int height)
-    {
-        int below = left[height - 1];
-        Span<int> weights = Av1SmoothPredictor.Weights.AsSpan(height, height);
-        int scale = 1 << Av1SmoothPredictor.WeightLog2Scale;
-
-        for (int row = 0; row < height; row++)
-        {
-            int weight = weights[row];
-            Span<short> destinationRow = destination.Slice(row * (int)stride, width);
-            for (int column = 0; column < width; column++)
-            {
-                int prediction = (above[column] * weight) + (below * (scale - weight));
-                destinationRow[column] = (short)Av1Math.DivideRound(prediction, Av1SmoothPredictor.WeightLog2Scale);
-            }
-        }
-    }
-
-    /// <summary>
-    /// Projects top reference samples into a directional zone 1 prediction block.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top reference samples, including any required extension.</param>
-    /// <param name="upsample">A value indicating whether the top reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative in Q6 precision.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    /// <param name="bitDepth">The number of bits used to represent each sample.</param>
-    private static void PredictDirectionalZone1(Span<short> destination, nuint stride, Span<short> above, bool upsample, int dx, int width, int height, int bitDepth)
-    {
-        int upsampleAbove = upsample ? 1 : 0;
-        int maxBasisX = (width + height - 1) << upsampleAbove;
-        int fractionBitCount = 6 - upsampleAbove;
-        int basisIncrement = 1 << upsampleAbove;
-        int maximum = (1 << bitDepth) - 1;
-        int x = dx;
-        ref short aboveRef = ref above[0];
-
-        for (int row = 0; row < height; row++)
-        {
-            Span<short> destinationRow = destination.Slice(row * (int)stride, width);
-
-            // AV1 retains six fractional projection bits, or five after reference upsampling.
-            // The interpolation weights sum to 32 because the low projection bit is discarded.
-            int basis = x >> fractionBitCount;
-            int shift = ((x << upsampleAbove) & 0x3F) >> 1;
-            for (int column = 0; column < width; column++)
-            {
-                if (basis < maxBasisX)
-                {
-                    int prediction = (Unsafe.Add(ref aboveRef, basis) * (32 - shift)) + (Unsafe.Add(ref aboveRef, basis + 1) * shift);
-                    destinationRow[column] = (short)Av1Math.Clamp(Av1Math.RoundPowerOf2(prediction, 5), 0, maximum);
-                }
-                else
-                {
-                    destinationRow[column] = Unsafe.Add(ref aboveRef, maxBasisX);
-                }
-
-                basis += basisIncrement;
-            }
-
-            x += dx;
-        }
-    }
-
-    /// <summary>
-    /// Projects top and left reference samples into a directional zone 2 prediction block.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top reference samples, including any required extension.</param>
-    /// <param name="left">The left reference samples, including any required extension.</param>
-    /// <param name="doUpsampleAbove">A value indicating whether the top reference samples were upsampled.</param>
-    /// <param name="doUpsampleLeft">A value indicating whether the left reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative in Q6 precision.</param>
-    /// <param name="dy">The vertical projection derivative in Q6 precision.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    /// <param name="bitDepth">The number of bits used to represent each sample.</param>
-    private static void PredictDirectionalZone2(Span<short> destination, nuint stride, Span<short> above, Span<short> left, bool doUpsampleAbove, bool doUpsampleLeft, int dx, int dy, int width, int height, int bitDepth)
-    {
-        int upsampleAbove = doUpsampleAbove ? 1 : 0;
-        int upsampleLeft = doUpsampleLeft ? 1 : 0;
-        int minBasisX = -(1 << upsampleAbove);
-        int fractionBitCountX = 6 - upsampleAbove;
-        int fractionBitCountY = 6 - upsampleLeft;
-        int basisIncrementX = 1 << upsampleAbove;
-        int maximum = (1 << bitDepth) - 1;
-        int x = -dx;
-        ref short aboveRef = ref above[0];
-        ref short leftRef = ref left[0];
-
-        for (int row = 0; row < height; row++)
-        {
-            Span<short> destinationRow = destination.Slice(row * (int)stride, width);
-            int basisX = x >> fractionBitCountX;
-            int y = (row << 6) - dy;
-            for (int column = 0; column < width; column++, basisX += basisIncrementX, y -= dy)
-            {
-                int prediction;
-
-                // A nonnegative top projection uses the above edge. Once the projection crosses
-                // the top-left corner, the same destination sample is projected from the left edge.
-                if (basisX >= minBasisX)
-                {
-                    int shift = ((x * (1 << upsampleAbove)) & 0x3F) >> 1;
-                    prediction = (Unsafe.Add(ref aboveRef, basisX) * (32 - shift)) + (Unsafe.Add(ref aboveRef, basisX + 1) * shift);
-                }
-                else
-                {
-                    int basisY = y >> fractionBitCountY;
-                    int shift = ((y * (1 << upsampleLeft)) & 0x3F) >> 1;
-                    prediction = (Unsafe.Add(ref leftRef, basisY) * (32 - shift)) + (Unsafe.Add(ref leftRef, basisY + 1) * shift);
-                }
-
-                destinationRow[column] = (short)Av1Math.Clamp(Av1Math.RoundPowerOf2(prediction, 5), 0, maximum);
-            }
-
-            x -= dx;
-        }
-    }
-
-    /// <summary>
-    /// Projects left reference samples into a directional zone 3 prediction block.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the predicted samples.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="left">The left reference samples, including any required extension.</param>
-    /// <param name="upsample">A value indicating whether the left reference samples were upsampled.</param>
-    /// <param name="dx">The horizontal projection derivative, which must be one in zone 3.</param>
-    /// <param name="dy">The vertical projection derivative in Q6 precision.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    /// <param name="bitDepth">The number of bits used to represent each sample.</param>
-    private static void PredictDirectionalZone3(Span<short> destination, nuint stride, Span<short> left, bool upsample, int dx, int dy, int width, int height, int bitDepth)
-    {
-        int upsampleLeft = upsample ? 1 : 0;
-        int maxBasisY = (width + height - 1) << upsampleLeft;
-        int fractionBitCount = 6 - upsampleLeft;
-        int basisIncrement = 1 << upsampleLeft;
-        int maximum = (1 << bitDepth) - 1;
-        int y = dy;
-        ref short leftRef = ref left[0];
-        Guard.IsTrue(dx == 1, nameof(dx), "Dx expected to be always equal to 1 for directional Zone 3 prediction.");
-
-        for (int column = 0; column < width; column++)
-        {
-            // Zone 3 is the transpose of zone 1: columns advance along the projected left edge,
-            // while rows advance through the reference samples for each destination column.
-            int basis = y >> fractionBitCount;
-            int shift = ((y << upsampleLeft) & 0x3F) >> 1;
-            for (int row = 0; row < height; row++)
-            {
-                int destinationOffset = (row * (int)stride) + column;
-                if (basis < maxBasisY)
-                {
-                    int prediction = (Unsafe.Add(ref leftRef, basis) * (32 - shift)) + (Unsafe.Add(ref leftRef, basis + 1) * shift);
-                    destination[destinationOffset] = (short)Av1Math.Clamp(Av1Math.RoundPowerOf2(prediction, 5), 0, maximum);
-                }
-                else
-                {
-                    destination[destinationOffset] = Unsafe.Add(ref leftRef, maxBasisY);
-                }
-
-                basis += basisIncrement;
-            }
-
-            y += dy;
-        }
-    }
-
-    /// <summary>
-    /// Fills a rectangular prediction block with one sample value.
-    /// </summary>
-    /// <param name="destination">The buffer that receives the sample value.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="width">The width of the prediction block in samples.</param>
-    /// <param name="height">The height of the prediction block in samples.</param>
-    /// <param name="value">The sample value written to every destination position.</param>
-    private static void Fill(Span<short> destination, nuint stride, int width, int height, short value)
-    {
-        for (int row = 0; row < height; row++)
-        {
-            destination.Slice(row * (int)stride, width).Fill(value);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1HorizontalPredictor.cs

@@ -1,72 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block by extending each left neighboring sample across its destination row.
-/// </summary>
-internal readonly struct Av1HorizontalPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of samples written to each destination row.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The number of left samples consumed and destination rows written.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1HorizontalPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1HorizontalPredictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1HorizontalPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1HorizontalPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block by extending its left edge horizontally.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The unused top-neighbor buffer required by the common predictor signature.</param>
-    /// <param name="left">The left neighboring samples.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1HorizontalPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    /// <remarks>SVT-AV1: <c>highbd_h_predictor</c>.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte leftRef = ref left[0];
-        ref byte destinationRef = ref destination[0];
-        uint width = (uint)this.blockWidth;
-        for (nuint r = 0; r < this.blockHeight; ++r)
-        {
-            Unsafe.InitBlock(ref destinationRef, Unsafe.Add(ref leftRef, r), width);
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.HorizontalOperator.cs

@@ -0,0 +1,54 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Implements AV1 horizontal intra prediction for scalar and SIMD lanes.
+    /// </summary>
+    internal readonly struct HorizontalOperator : IAv1IntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1PredictionMode Mode => Av1PredictionMode.Horizontal;
+
+        /// <inheritdoc/>
+        public static Av1IntraPredictionInputs Inputs => Av1IntraPredictionInputs.Left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte Predict(byte top, byte left, byte topLeft, byte topRight, byte bottomLeft, int columnWeight, int rowWeight) => left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<byte> Predict(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft, Vector128<byte> topRight, Vector128<byte> bottomLeft, ref int columnWeights, int rowWeight) => left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<byte> Predict(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft, Vector256<byte> topRight, Vector256<byte> bottomLeft, ref int columnWeights, int rowWeight) => left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<byte> Predict(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft, Vector512<byte> topRight, Vector512<byte> bottomLeft, ref int columnWeights, int rowWeight) => left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Predict(short top, short left, short topLeft, short topRight, short bottomLeft, int columnWeight, int rowWeight) => left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> Predict(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft, Vector128<short> topRight, Vector128<short> bottomLeft, ref int columnWeights, int rowWeight) => left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<short> Predict(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft, Vector256<short> topRight, Vector256<short> bottomLeft, ref int columnWeights, int rowWeight) => left;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<short> Predict(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft, Vector512<short> topRight, Vector512<short> bottomLeft, ref int columnWeights, int rowWeight) => left;
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.Operator.cs

@@ -0,0 +1,344 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Applies one closed non-directional AV1 prediction operator using the widest available SIMD width.
+    /// </summary>
+    /// <typeparam name="TOperator">The prediction-mode-specific arithmetic.</typeparam>
+    internal sealed class Av1IntraPredictor<TOperator> : Av1IntraPredictorBase
+        where TOperator : struct, IAv1IntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public override Av1PredictionMode Mode => TOperator.Mode;
+
+        /// <inheritdoc/>
+        public override void Predict(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height)
+        {
+            ref byte destinationBase = ref MemoryMarshal.GetReference(destination);
+            ref byte topBase = ref MemoryMarshal.GetReference(above);
+            ref byte leftBase = ref MemoryMarshal.GetReference(left);
+            ref int columnWeightBase = ref MemoryMarshal.GetReference(SmoothWeights[width..]);
+
+            Av1IntraPredictionInputs inputs = TOperator.Inputs;
+            bool usesTop = (inputs & Av1IntraPredictionInputs.Top) != 0;
+            bool usesLeft = (inputs & Av1IntraPredictionInputs.Left) != 0;
+            bool usesTopLeft = (inputs & Av1IntraPredictionInputs.TopLeft) != 0;
+            bool usesTopRight = (inputs & Av1IntraPredictionInputs.TopRight) != 0;
+            bool usesBottomLeft = (inputs & Av1IntraPredictionInputs.BottomLeft) != 0;
+            bool usesColumnWeight = (inputs & Av1IntraPredictionInputs.ColumnWeight) != 0;
+            bool usesRowWeight = (inputs & Av1IntraPredictionInputs.RowWeight) != 0;
+
+            byte topLeft = usesTopLeft ? Unsafe.Subtract(ref topBase, 1) : default;
+            byte topRight = usesTopRight ? Unsafe.Add(ref topBase, width - 1) : default;
+            byte bottomLeft = usesBottomLeft ? Unsafe.Add(ref leftBase, height - 1) : default;
+            int processedColumns = 0;
+
+            if (Vector512.IsHardwareAccelerated)
+            {
+                int vectorizedColumns = width - (width % Vector512<byte>.Count);
+                if (vectorizedColumns > 0)
+                {
+                    Vector512<byte> topLeftVector = usesTopLeft ? Vector512.Create(topLeft) : default;
+                    Vector512<byte> topRightVector = usesTopRight ? Vector512.Create(topRight) : default;
+                    Vector512<byte> bottomLeftVector = usesBottomLeft ? Vector512.Create(bottomLeft) : default;
+
+                    for (int row = 0; row < height; row++)
+                    {
+                        Vector512<byte> leftVector = usesLeft ? Vector512.Create(Unsafe.Add(ref leftBase, row)) : default;
+                        int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                        ref byte destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                        for (int column = 0; column < vectorizedColumns; column += Vector512<byte>.Count)
+                        {
+                            Vector512<byte> top = usesTop ? Vector512.LoadUnsafe(ref topBase, (nuint)column) : default;
+                            ref int columnWeights = ref usesColumnWeight ? ref Unsafe.Add(ref columnWeightBase, column) : ref columnWeightBase;
+                            Vector512<byte> prediction = TOperator.Predict(top, leftVector, topLeftVector, topRightVector, bottomLeftVector, ref columnWeights, rowWeight);
+                            prediction.StoreUnsafe(ref destinationRow, (nuint)column);
+                        }
+                    }
+
+                    processedColumns = vectorizedColumns;
+                }
+            }
+
+            if (Vector256.IsHardwareAccelerated)
+            {
+                int remainingColumns = width - processedColumns;
+                int vectorizedColumns = remainingColumns - (remainingColumns % Vector256<byte>.Count);
+                if (vectorizedColumns > 0)
+                {
+                    Vector256<byte> topLeftVector = usesTopLeft ? Vector256.Create(topLeft) : default;
+                    Vector256<byte> topRightVector = usesTopRight ? Vector256.Create(topRight) : default;
+                    Vector256<byte> bottomLeftVector = usesBottomLeft ? Vector256.Create(bottomLeft) : default;
+                    int endColumn = processedColumns + vectorizedColumns;
+
+                    for (int row = 0; row < height; row++)
+                    {
+                        Vector256<byte> leftVector = usesLeft ? Vector256.Create(Unsafe.Add(ref leftBase, row)) : default;
+                        int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                        ref byte destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                        for (int column = processedColumns; column < endColumn; column += Vector256<byte>.Count)
+                        {
+                            Vector256<byte> top = usesTop ? Vector256.LoadUnsafe(ref topBase, (nuint)column) : default;
+                            ref int columnWeights = ref usesColumnWeight ? ref Unsafe.Add(ref columnWeightBase, column) : ref columnWeightBase;
+                            Vector256<byte> prediction = TOperator.Predict(top, leftVector, topLeftVector, topRightVector, bottomLeftVector, ref columnWeights, rowWeight);
+                            prediction.StoreUnsafe(ref destinationRow, (nuint)column);
+                        }
+                    }
+
+                    processedColumns = endColumn;
+                }
+            }
+
+            if (Vector128.IsHardwareAccelerated)
+            {
+                int remainingColumns = width - processedColumns;
+                int vectorizedColumns = remainingColumns - (remainingColumns % Vector128<byte>.Count);
+                if (vectorizedColumns > 0)
+                {
+                    Vector128<byte> topLeftVector = usesTopLeft ? Vector128.Create(topLeft) : default;
+                    Vector128<byte> topRightVector = usesTopRight ? Vector128.Create(topRight) : default;
+                    Vector128<byte> bottomLeftVector = usesBottomLeft ? Vector128.Create(bottomLeft) : default;
+                    int endColumn = processedColumns + vectorizedColumns;
+
+                    for (int row = 0; row < height; row++)
+                    {
+                        Vector128<byte> leftVector = usesLeft ? Vector128.Create(Unsafe.Add(ref leftBase, row)) : default;
+                        int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                        ref byte destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                        for (int column = processedColumns; column < endColumn; column += Vector128<byte>.Count)
+                        {
+                            Vector128<byte> top = usesTop ? Vector128.LoadUnsafe(ref topBase, (nuint)column) : default;
+                            ref int columnWeights = ref usesColumnWeight ? ref Unsafe.Add(ref columnWeightBase, column) : ref columnWeightBase;
+                            Vector128<byte> prediction = TOperator.Predict(top, leftVector, topLeftVector, topRightVector, bottomLeftVector, ref columnWeights, rowWeight);
+                            prediction.StoreUnsafe(ref destinationRow, (nuint)column);
+                        }
+                    }
+
+                    processedColumns = endColumn;
+                }
+            }
+
+            // AV1 dimensions are multiples of four. The tail is normally zero on SIMD hardware, but retaining the
+            // scalar continuation keeps the traversal correct when intrinsics are disabled by FeatureTestRunner.
+            for (int row = 0; row < height; row++)
+            {
+                byte leftSample = usesLeft ? Unsafe.Add(ref leftBase, row) : default;
+                int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                ref byte destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                for (int column = processedColumns; column < width; column++)
+                {
+                    byte top = usesTop ? Unsafe.Add(ref topBase, column) : default;
+                    int columnWeight = usesColumnWeight ? Unsafe.Add(ref columnWeightBase, column) : 0;
+                    Unsafe.Add(ref destinationRow, column) = TOperator.Predict(top, leftSample, topLeft, topRight, bottomLeft, columnWeight, rowWeight);
+                }
+            }
+        }
+
+        /// <inheritdoc/>
+        public override void Predict(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height)
+        {
+            ref short destinationBase = ref MemoryMarshal.GetReference(destination);
+            ref short topBase = ref MemoryMarshal.GetReference(above);
+            ref short leftBase = ref MemoryMarshal.GetReference(left);
+            ref int columnWeightBase = ref MemoryMarshal.GetReference(SmoothWeights[width..]);
+
+            Av1IntraPredictionInputs inputs = TOperator.Inputs;
+            bool usesTop = (inputs & Av1IntraPredictionInputs.Top) != 0;
+            bool usesLeft = (inputs & Av1IntraPredictionInputs.Left) != 0;
+            bool usesTopLeft = (inputs & Av1IntraPredictionInputs.TopLeft) != 0;
+            bool usesTopRight = (inputs & Av1IntraPredictionInputs.TopRight) != 0;
+            bool usesBottomLeft = (inputs & Av1IntraPredictionInputs.BottomLeft) != 0;
+            bool usesColumnWeight = (inputs & Av1IntraPredictionInputs.ColumnWeight) != 0;
+            bool usesRowWeight = (inputs & Av1IntraPredictionInputs.RowWeight) != 0;
+
+            short topLeft = usesTopLeft ? Unsafe.Subtract(ref topBase, 1) : default;
+            short topRight = usesTopRight ? Unsafe.Add(ref topBase, width - 1) : default;
+            short bottomLeft = usesBottomLeft ? Unsafe.Add(ref leftBase, height - 1) : default;
+            int processedColumns = 0;
+
+            if (Vector512.IsHardwareAccelerated)
+            {
+                int vectorizedColumns = width - (width % Vector512<short>.Count);
+                if (vectorizedColumns > 0)
+                {
+                    Vector512<short> topLeftVector = usesTopLeft ? Vector512.Create(topLeft) : default;
+                    Vector512<short> topRightVector = usesTopRight ? Vector512.Create(topRight) : default;
+                    Vector512<short> bottomLeftVector = usesBottomLeft ? Vector512.Create(bottomLeft) : default;
+
+                    for (int row = 0; row < height; row++)
+                    {
+                        Vector512<short> leftVector = usesLeft ? Vector512.Create(Unsafe.Add(ref leftBase, row)) : default;
+                        int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                        ref short destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                        for (int column = 0; column < vectorizedColumns; column += Vector512<short>.Count)
+                        {
+                            Vector512<short> top = usesTop ? Vector512.LoadUnsafe(ref topBase, (nuint)column) : default;
+                            ref int columnWeights = ref usesColumnWeight ? ref Unsafe.Add(ref columnWeightBase, column) : ref columnWeightBase;
+                            Vector512<short> prediction = TOperator.Predict(top, leftVector, topLeftVector, topRightVector, bottomLeftVector, ref columnWeights, rowWeight);
+                            prediction.StoreUnsafe(ref destinationRow, (nuint)column);
+                        }
+                    }
+
+                    processedColumns = vectorizedColumns;
+                }
+            }
+
+            if (Vector256.IsHardwareAccelerated)
+            {
+                int remainingColumns = width - processedColumns;
+                int vectorizedColumns = remainingColumns - (remainingColumns % Vector256<short>.Count);
+                if (vectorizedColumns > 0)
+                {
+                    Vector256<short> topLeftVector = usesTopLeft ? Vector256.Create(topLeft) : default;
+                    Vector256<short> topRightVector = usesTopRight ? Vector256.Create(topRight) : default;
+                    Vector256<short> bottomLeftVector = usesBottomLeft ? Vector256.Create(bottomLeft) : default;
+                    int endColumn = processedColumns + vectorizedColumns;
+
+                    for (int row = 0; row < height; row++)
+                    {
+                        Vector256<short> leftVector = usesLeft ? Vector256.Create(Unsafe.Add(ref leftBase, row)) : default;
+                        int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                        ref short destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                        for (int column = processedColumns; column < endColumn; column += Vector256<short>.Count)
+                        {
+                            Vector256<short> top = usesTop ? Vector256.LoadUnsafe(ref topBase, (nuint)column) : default;
+                            ref int columnWeights = ref usesColumnWeight ? ref Unsafe.Add(ref columnWeightBase, column) : ref columnWeightBase;
+                            Vector256<short> prediction = TOperator.Predict(top, leftVector, topLeftVector, topRightVector, bottomLeftVector, ref columnWeights, rowWeight);
+                            prediction.StoreUnsafe(ref destinationRow, (nuint)column);
+                        }
+                    }
+
+                    processedColumns = endColumn;
+                }
+            }
+
+            if (Vector128.IsHardwareAccelerated)
+            {
+                int remainingColumns = width - processedColumns;
+                int vectorizedColumns = remainingColumns - (remainingColumns % Vector128<short>.Count);
+                if (vectorizedColumns > 0)
+                {
+                    Vector128<short> topLeftVector = usesTopLeft ? Vector128.Create(topLeft) : default;
+                    Vector128<short> topRightVector = usesTopRight ? Vector128.Create(topRight) : default;
+                    Vector128<short> bottomLeftVector = usesBottomLeft ? Vector128.Create(bottomLeft) : default;
+                    int endColumn = processedColumns + vectorizedColumns;
+
+                    for (int row = 0; row < height; row++)
+                    {
+                        Vector128<short> leftVector = usesLeft ? Vector128.Create(Unsafe.Add(ref leftBase, row)) : default;
+                        int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                        ref short destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                        for (int column = processedColumns; column < endColumn; column += Vector128<short>.Count)
+                        {
+                            Vector128<short> top = usesTop ? Vector128.LoadUnsafe(ref topBase, (nuint)column) : default;
+                            ref int columnWeights = ref usesColumnWeight ? ref Unsafe.Add(ref columnWeightBase, column) : ref columnWeightBase;
+                            Vector128<short> prediction = TOperator.Predict(top, leftVector, topLeftVector, topRightVector, bottomLeftVector, ref columnWeights, rowWeight);
+                            prediction.StoreUnsafe(ref destinationRow, (nuint)column);
+                        }
+                    }
+
+                    processedColumns = endColumn;
+                }
+            }
+
+            for (int row = 0; row < height; row++)
+            {
+                short leftSample = usesLeft ? Unsafe.Add(ref leftBase, row) : default;
+                int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                ref short destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                for (int column = processedColumns; column < width; column++)
+                {
+                    short top = usesTop ? Unsafe.Add(ref topBase, column) : default;
+                    int columnWeight = usesColumnWeight ? Unsafe.Add(ref columnWeightBase, column) : 0;
+                    Unsafe.Add(ref destinationRow, column) = TOperator.Predict(top, leftSample, topLeft, topRight, bottomLeft, columnWeight, rowWeight);
+                }
+            }
+        }
+
+        /// <inheritdoc/>
+        public override void PredictScalar(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height)
+        {
+            ref byte destinationBase = ref MemoryMarshal.GetReference(destination);
+            ref byte topBase = ref MemoryMarshal.GetReference(above);
+            ref byte leftBase = ref MemoryMarshal.GetReference(left);
+            ref int columnWeightBase = ref MemoryMarshal.GetReference(SmoothWeights[width..]);
+
+            Av1IntraPredictionInputs inputs = TOperator.Inputs;
+            bool usesTop = (inputs & Av1IntraPredictionInputs.Top) != 0;
+            bool usesLeft = (inputs & Av1IntraPredictionInputs.Left) != 0;
+            bool usesTopLeft = (inputs & Av1IntraPredictionInputs.TopLeft) != 0;
+            bool usesTopRight = (inputs & Av1IntraPredictionInputs.TopRight) != 0;
+            bool usesBottomLeft = (inputs & Av1IntraPredictionInputs.BottomLeft) != 0;
+            bool usesColumnWeight = (inputs & Av1IntraPredictionInputs.ColumnWeight) != 0;
+            bool usesRowWeight = (inputs & Av1IntraPredictionInputs.RowWeight) != 0;
+            byte topLeft = usesTopLeft ? Unsafe.Subtract(ref topBase, 1) : default;
+            byte topRight = usesTopRight ? Unsafe.Add(ref topBase, width - 1) : default;
+            byte bottomLeft = usesBottomLeft ? Unsafe.Add(ref leftBase, height - 1) : default;
+
+            for (int row = 0; row < height; row++)
+            {
+                byte leftSample = usesLeft ? Unsafe.Add(ref leftBase, row) : default;
+                int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                ref byte destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                for (int column = 0; column < width; column++)
+                {
+                    byte top = usesTop ? Unsafe.Add(ref topBase, column) : default;
+                    int columnWeight = usesColumnWeight ? Unsafe.Add(ref columnWeightBase, column) : 0;
+                    Unsafe.Add(ref destinationRow, column) = TOperator.Predict(top, leftSample, topLeft, topRight, bottomLeft, columnWeight, rowWeight);
+                }
+            }
+        }
+
+        /// <inheritdoc/>
+        public override void PredictScalar(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height)
+        {
+            ref short destinationBase = ref MemoryMarshal.GetReference(destination);
+            ref short topBase = ref MemoryMarshal.GetReference(above);
+            ref short leftBase = ref MemoryMarshal.GetReference(left);
+            ref int columnWeightBase = ref MemoryMarshal.GetReference(SmoothWeights[width..]);
+
+            Av1IntraPredictionInputs inputs = TOperator.Inputs;
+            bool usesTop = (inputs & Av1IntraPredictionInputs.Top) != 0;
+            bool usesLeft = (inputs & Av1IntraPredictionInputs.Left) != 0;
+            bool usesTopLeft = (inputs & Av1IntraPredictionInputs.TopLeft) != 0;
+            bool usesTopRight = (inputs & Av1IntraPredictionInputs.TopRight) != 0;
+            bool usesBottomLeft = (inputs & Av1IntraPredictionInputs.BottomLeft) != 0;
+            bool usesColumnWeight = (inputs & Av1IntraPredictionInputs.ColumnWeight) != 0;
+            bool usesRowWeight = (inputs & Av1IntraPredictionInputs.RowWeight) != 0;
+            short topLeft = usesTopLeft ? Unsafe.Subtract(ref topBase, 1) : default;
+            short topRight = usesTopRight ? Unsafe.Add(ref topBase, width - 1) : default;
+            short bottomLeft = usesBottomLeft ? Unsafe.Add(ref leftBase, height - 1) : default;
+
+            for (int row = 0; row < height; row++)
+            {
+                short leftSample = usesLeft ? Unsafe.Add(ref leftBase, row) : default;
+                int rowWeight = usesRowWeight ? SmoothWeights[height + row] : 0;
+                ref short destinationRow = ref Unsafe.Add(ref destinationBase, row * destinationStride);
+
+                for (int column = 0; column < width; column++)
+                {
+                    short top = usesTop ? Unsafe.Add(ref topBase, column) : default;
+                    int columnWeight = usesColumnWeight ? Unsafe.Add(ref columnWeightBase, column) : 0;
+                    Unsafe.Add(ref destinationRow, column) = TOperator.Predict(top, leftSample, topLeft, topRight, bottomLeft, columnWeight, rowWeight);
+                }
+            }
+        }
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.OperatorContract.cs

@@ -0,0 +1,180 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Identifies the neighboring inputs consumed by an AV1 intra-prediction operator.
+    /// </summary>
+    [Flags]
+    internal enum Av1IntraPredictionInputs
+    {
+        /// <summary>
+        /// The operator does not consume neighboring samples.
+        /// </summary>
+        None = 0,
+
+        /// <summary>
+        /// The operator consumes samples from the top reference.
+        /// </summary>
+        Top = 1,
+
+        /// <summary>
+        /// The operator consumes samples from the left reference.
+        /// </summary>
+        Left = 2,
+
+        /// <summary>
+        /// The operator consumes the shared top-left reference.
+        /// </summary>
+        TopLeft = 4,
+
+        /// <summary>
+        /// The operator consumes the final top reference.
+        /// </summary>
+        TopRight = 8,
+
+        /// <summary>
+        /// The operator consumes the final left reference.
+        /// </summary>
+        BottomLeft = 16,
+
+        /// <summary>
+        /// The operator consumes the horizontal smooth weights.
+        /// </summary>
+        ColumnWeight = 32,
+
+        /// <summary>
+        /// The operator consumes the vertical smooth weights.
+        /// </summary>
+        RowWeight = 64,
+    }
+
+    /// <summary>
+    /// Defines the scalar and SIMD arithmetic for one non-directional AV1 intra-prediction mode.
+    /// </summary>
+    /// <remarks>
+    /// Each overload performs the same lane-wise operation. The generic predictor traversal selects the widest
+    /// available overload, and the JIT specializes each static interface call for the closed operator type.
+    /// </remarks>
+    internal interface IAv1IntraPredictionOperator
+    {
+        /// <summary>
+        /// Gets the prediction mode implemented by the operator.
+        /// </summary>
+        public static abstract Av1PredictionMode Mode { get; }
+
+        /// <summary>
+        /// Gets the neighboring inputs consumed by the operator.
+        /// </summary>
+        public static abstract Av1IntraPredictionInputs Inputs { get; }
+
+        /// <summary>
+        /// Predicts one 8-bit sample when hardware vectorization is unavailable.
+        /// </summary>
+        /// <param name="top">The top reference sample.</param>
+        /// <param name="left">The left reference sample.</param>
+        /// <param name="topLeft">The shared top-left reference sample.</param>
+        /// <param name="topRight">The final top reference sample.</param>
+        /// <param name="bottomLeft">The final left reference sample.</param>
+        /// <param name="columnWeight">The horizontal Q8 smooth weight.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted sample.</returns>
+        public static abstract byte Predict(byte top, byte left, byte topLeft, byte topRight, byte bottomLeft, int columnWeight, int rowWeight);
+
+        /// <summary>
+        /// Predicts sixteen 8-bit samples in parallel.
+        /// </summary>
+        /// <param name="top">The top reference samples.</param>
+        /// <param name="left">The left reference sample in every lane.</param>
+        /// <param name="topLeft">The shared top-left reference sample in every lane.</param>
+        /// <param name="topRight">The final top reference sample in every lane.</param>
+        /// <param name="bottomLeft">The final left reference sample in every lane.</param>
+        /// <param name="columnWeights">The first horizontal Q8 smooth weight for these lanes.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted samples.</returns>
+        public static abstract Vector128<byte> Predict(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft, Vector128<byte> topRight, Vector128<byte> bottomLeft, ref int columnWeights, int rowWeight);
+
+        /// <summary>
+        /// Predicts thirty-two 8-bit samples in parallel.
+        /// </summary>
+        /// <param name="top">The top reference samples.</param>
+        /// <param name="left">The left reference sample in every lane.</param>
+        /// <param name="topLeft">The shared top-left reference sample in every lane.</param>
+        /// <param name="topRight">The final top reference sample in every lane.</param>
+        /// <param name="bottomLeft">The final left reference sample in every lane.</param>
+        /// <param name="columnWeights">The first horizontal Q8 smooth weight for these lanes.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted samples.</returns>
+        public static abstract Vector256<byte> Predict(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft, Vector256<byte> topRight, Vector256<byte> bottomLeft, ref int columnWeights, int rowWeight);
+
+        /// <summary>
+        /// Predicts sixty-four 8-bit samples in parallel.
+        /// </summary>
+        /// <param name="top">The top reference samples.</param>
+        /// <param name="left">The left reference sample in every lane.</param>
+        /// <param name="topLeft">The shared top-left reference sample in every lane.</param>
+        /// <param name="topRight">The final top reference sample in every lane.</param>
+        /// <param name="bottomLeft">The final left reference sample in every lane.</param>
+        /// <param name="columnWeights">The first horizontal Q8 smooth weight for these lanes.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted samples.</returns>
+        public static abstract Vector512<byte> Predict(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft, Vector512<byte> topRight, Vector512<byte> bottomLeft, ref int columnWeights, int rowWeight);
+
+        /// <summary>
+        /// Predicts one high-bit-depth sample when hardware vectorization is unavailable.
+        /// </summary>
+        /// <param name="top">The top reference sample.</param>
+        /// <param name="left">The left reference sample.</param>
+        /// <param name="topLeft">The shared top-left reference sample.</param>
+        /// <param name="topRight">The final top reference sample.</param>
+        /// <param name="bottomLeft">The final left reference sample.</param>
+        /// <param name="columnWeight">The horizontal Q8 smooth weight.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted sample.</returns>
+        public static abstract short Predict(short top, short left, short topLeft, short topRight, short bottomLeft, int columnWeight, int rowWeight);
+
+        /// <summary>
+        /// Predicts eight high-bit-depth samples in parallel.
+        /// </summary>
+        /// <param name="top">The top reference samples.</param>
+        /// <param name="left">The left reference sample in every lane.</param>
+        /// <param name="topLeft">The shared top-left reference sample in every lane.</param>
+        /// <param name="topRight">The final top reference sample in every lane.</param>
+        /// <param name="bottomLeft">The final left reference sample in every lane.</param>
+        /// <param name="columnWeights">The first horizontal Q8 smooth weight for these lanes.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted samples.</returns>
+        public static abstract Vector128<short> Predict(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft, Vector128<short> topRight, Vector128<short> bottomLeft, ref int columnWeights, int rowWeight);
+
+        /// <summary>
+        /// Predicts sixteen high-bit-depth samples in parallel.
+        /// </summary>
+        /// <param name="top">The top reference samples.</param>
+        /// <param name="left">The left reference sample in every lane.</param>
+        /// <param name="topLeft">The shared top-left reference sample in every lane.</param>
+        /// <param name="topRight">The final top reference sample in every lane.</param>
+        /// <param name="bottomLeft">The final left reference sample in every lane.</param>
+        /// <param name="columnWeights">The first horizontal Q8 smooth weight for these lanes.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted samples.</returns>
+        public static abstract Vector256<short> Predict(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft, Vector256<short> topRight, Vector256<short> bottomLeft, ref int columnWeights, int rowWeight);
+
+        /// <summary>
+        /// Predicts thirty-two high-bit-depth samples in parallel.
+        /// </summary>
+        /// <param name="top">The top reference samples.</param>
+        /// <param name="left">The left reference sample in every lane.</param>
+        /// <param name="topLeft">The shared top-left reference sample in every lane.</param>
+        /// <param name="topRight">The final top reference sample in every lane.</param>
+        /// <param name="bottomLeft">The final left reference sample in every lane.</param>
+        /// <param name="columnWeights">The first horizontal Q8 smooth weight for these lanes.</param>
+        /// <param name="rowWeight">The vertical Q8 smooth weight.</param>
+        /// <returns>The predicted samples.</returns>
+        public static abstract Vector512<short> Predict(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft, Vector512<short> topRight, Vector512<short> bottomLeft, ref int columnWeights, int rowWeight);
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.Packing.cs

@@ -0,0 +1,166 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+/// <summary>
+/// Widens AV1 sample vectors for fixed-point prediction arithmetic and narrows completed results.
+/// </summary>
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Widens sixteen 8-bit samples into four 32-bit vectors.
+    /// </summary>
+    /// <param name="source">The packed samples.</param>
+    /// <param name="result0">The first four widened samples.</param>
+    /// <param name="result1">The second four widened samples.</param>
+    /// <param name="result2">The third four widened samples.</param>
+    /// <param name="result3">The fourth four widened samples.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void Widen(Vector128<byte> source, out Vector128<int> result0, out Vector128<int> result1, out Vector128<int> result2, out Vector128<int> result3)
+    {
+        (Vector128<ushort> low, Vector128<ushort> high) = Vector128.Widen(source);
+        (Vector128<uint> low0, Vector128<uint> low1) = Vector128.Widen(low);
+        (Vector128<uint> high0, Vector128<uint> high1) = Vector128.Widen(high);
+        result0 = low0.AsInt32();
+        result1 = low1.AsInt32();
+        result2 = high0.AsInt32();
+        result3 = high1.AsInt32();
+    }
+
+    /// <summary>
+    /// Widens thirty-two 8-bit samples into four 32-bit vectors.
+    /// </summary>
+    /// <param name="source">The packed samples.</param>
+    /// <param name="result0">The first eight widened samples.</param>
+    /// <param name="result1">The second eight widened samples.</param>
+    /// <param name="result2">The third eight widened samples.</param>
+    /// <param name="result3">The fourth eight widened samples.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void Widen(Vector256<byte> source, out Vector256<int> result0, out Vector256<int> result1, out Vector256<int> result2, out Vector256<int> result3)
+    {
+        (Vector256<ushort> low, Vector256<ushort> high) = Vector256.Widen(source);
+        (Vector256<uint> low0, Vector256<uint> low1) = Vector256.Widen(low);
+        (Vector256<uint> high0, Vector256<uint> high1) = Vector256.Widen(high);
+        result0 = low0.AsInt32();
+        result1 = low1.AsInt32();
+        result2 = high0.AsInt32();
+        result3 = high1.AsInt32();
+    }
+
+    /// <summary>
+    /// Widens sixty-four 8-bit samples into four 32-bit vectors.
+    /// </summary>
+    /// <param name="source">The packed samples.</param>
+    /// <param name="result0">The first sixteen widened samples.</param>
+    /// <param name="result1">The second sixteen widened samples.</param>
+    /// <param name="result2">The third sixteen widened samples.</param>
+    /// <param name="result3">The fourth sixteen widened samples.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void Widen(Vector512<byte> source, out Vector512<int> result0, out Vector512<int> result1, out Vector512<int> result2, out Vector512<int> result3)
+    {
+        (Vector512<ushort> low, Vector512<ushort> high) = Vector512.Widen(source);
+        (Vector512<uint> low0, Vector512<uint> low1) = Vector512.Widen(low);
+        (Vector512<uint> high0, Vector512<uint> high1) = Vector512.Widen(high);
+        result0 = low0.AsInt32();
+        result1 = low1.AsInt32();
+        result2 = high0.AsInt32();
+        result3 = high1.AsInt32();
+    }
+
+    /// <summary>
+    /// Widens eight high-bit-depth samples into two 32-bit vectors.
+    /// </summary>
+    /// <param name="source">The packed samples.</param>
+    /// <param name="result0">The first four widened samples.</param>
+    /// <param name="result1">The second four widened samples.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void Widen(Vector128<short> source, out Vector128<int> result0, out Vector128<int> result1)
+        => (result0, result1) = Vector128.Widen(source);
+
+    /// <summary>
+    /// Widens sixteen high-bit-depth samples into two 32-bit vectors.
+    /// </summary>
+    /// <param name="source">The packed samples.</param>
+    /// <param name="result0">The first eight widened samples.</param>
+    /// <param name="result1">The second eight widened samples.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void Widen(Vector256<short> source, out Vector256<int> result0, out Vector256<int> result1)
+        => (result0, result1) = Vector256.Widen(source);
+
+    /// <summary>
+    /// Widens thirty-two high-bit-depth samples into two 32-bit vectors.
+    /// </summary>
+    /// <param name="source">The packed samples.</param>
+    /// <param name="result0">The first sixteen widened samples.</param>
+    /// <param name="result1">The second sixteen widened samples.</param>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static void Widen(Vector512<short> source, out Vector512<int> result0, out Vector512<int> result1)
+        => (result0, result1) = Vector512.Widen(source);
+
+    /// <summary>
+    /// Narrows four 32-bit vectors into sixteen 8-bit samples.
+    /// </summary>
+    /// <param name="source0">The first four samples.</param>
+    /// <param name="source1">The second four samples.</param>
+    /// <param name="source2">The third four samples.</param>
+    /// <param name="source3">The fourth four samples.</param>
+    /// <returns>The packed samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector128<byte> Narrow(Vector128<int> source0, Vector128<int> source1, Vector128<int> source2, Vector128<int> source3)
+        => Vector128.Narrow(Vector128.Narrow(source0.AsUInt32(), source1.AsUInt32()), Vector128.Narrow(source2.AsUInt32(), source3.AsUInt32()));
+
+    /// <summary>
+    /// Narrows four 32-bit vectors into thirty-two 8-bit samples.
+    /// </summary>
+    /// <param name="source0">The first eight samples.</param>
+    /// <param name="source1">The second eight samples.</param>
+    /// <param name="source2">The third eight samples.</param>
+    /// <param name="source3">The fourth eight samples.</param>
+    /// <returns>The packed samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector256<byte> Narrow(Vector256<int> source0, Vector256<int> source1, Vector256<int> source2, Vector256<int> source3)
+        => Vector256.Narrow(Vector256.Narrow(source0.AsUInt32(), source1.AsUInt32()), Vector256.Narrow(source2.AsUInt32(), source3.AsUInt32()));
+
+    /// <summary>
+    /// Narrows four 32-bit vectors into sixty-four 8-bit samples.
+    /// </summary>
+    /// <param name="source0">The first sixteen samples.</param>
+    /// <param name="source1">The second sixteen samples.</param>
+    /// <param name="source2">The third sixteen samples.</param>
+    /// <param name="source3">The fourth sixteen samples.</param>
+    /// <returns>The packed samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector512<byte> Narrow(Vector512<int> source0, Vector512<int> source1, Vector512<int> source2, Vector512<int> source3)
+        => Vector512.Narrow(Vector512.Narrow(source0.AsUInt32(), source1.AsUInt32()), Vector512.Narrow(source2.AsUInt32(), source3.AsUInt32()));
+
+    /// <summary>
+    /// Narrows two 32-bit vectors into eight high-bit-depth samples.
+    /// </summary>
+    /// <param name="source0">The first four samples.</param>
+    /// <param name="source1">The second four samples.</param>
+    /// <returns>The packed samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector128<short> Narrow(Vector128<int> source0, Vector128<int> source1) => Vector128.Narrow(source0, source1);
+
+    /// <summary>
+    /// Narrows two 32-bit vectors into sixteen high-bit-depth samples.
+    /// </summary>
+    /// <param name="source0">The first eight samples.</param>
+    /// <param name="source1">The second eight samples.</param>
+    /// <returns>The packed samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector256<short> Narrow(Vector256<int> source0, Vector256<int> source1) => Vector256.Narrow(source0, source1);
+
+    /// <summary>
+    /// Narrows two 32-bit vectors into thirty-two high-bit-depth samples.
+    /// </summary>
+    /// <param name="source0">The first sixteen samples.</param>
+    /// <param name="source1">The second sixteen samples.</param>
+    /// <returns>The packed samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Vector512<short> Narrow(Vector512<int> source0, Vector512<int> source1) => Vector512.Narrow(source0, source1);
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.PaethOperator.cs

@@ -0,0 +1,209 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Implements AV1 Paeth intra prediction for scalar and SIMD lanes.
+    /// </summary>
+    internal readonly struct PaethOperator : IAv1IntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1PredictionMode Mode => Av1PredictionMode.Paeth;
+
+        /// <inheritdoc/>
+        public static Av1IntraPredictionInputs Inputs
+            => Av1IntraPredictionInputs.Top | Av1IntraPredictionInputs.Left | Av1IntraPredictionInputs.TopLeft;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte Predict(byte top, byte left, byte topLeft, byte topRight, byte bottomLeft, int columnWeight, int rowWeight)
+        {
+            int basis = top + left - topLeft;
+            int distanceLeft = Math.Abs(basis - left);
+            int distanceTop = Math.Abs(basis - top);
+            int distanceTopLeft = Math.Abs(basis - topLeft);
+
+            // AV1 resolves equal distances in left, top, top-left order.
+            return distanceLeft <= distanceTop && distanceLeft <= distanceTopLeft ? left : distanceTop <= distanceTopLeft ? top : topLeft;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<byte> Predict(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft, Vector128<byte> topRight, Vector128<byte> bottomLeft, ref int columnWeights, int rowWeight)
+            => PredictPaeth(top, left, topLeft);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<byte> Predict(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft, Vector256<byte> topRight, Vector256<byte> bottomLeft, ref int columnWeights, int rowWeight)
+            => PredictPaeth(top, left, topLeft);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<byte> Predict(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft, Vector512<byte> topRight, Vector512<byte> bottomLeft, ref int columnWeights, int rowWeight)
+            => PredictPaeth(top, left, topLeft);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Predict(short top, short left, short topLeft, short topRight, short bottomLeft, int columnWeight, int rowWeight)
+        {
+            int basis = top + left - topLeft;
+            int distanceLeft = Math.Abs(basis - left);
+            int distanceTop = Math.Abs(basis - top);
+            int distanceTopLeft = Math.Abs(basis - topLeft);
+
+            // High-bit-depth prediction has the same tie order as the 8-bit process.
+            return distanceLeft <= distanceTop && distanceLeft <= distanceTopLeft ? left : distanceTop <= distanceTopLeft ? top : topLeft;
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> Predict(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft, Vector128<short> topRight, Vector128<short> bottomLeft, ref int columnWeights, int rowWeight)
+            => PredictPaeth(top, left, topLeft);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<short> Predict(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft, Vector256<short> topRight, Vector256<short> bottomLeft, ref int columnWeights, int rowWeight)
+            => PredictPaeth(top, left, topLeft);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<short> Predict(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft, Vector512<short> topRight, Vector512<short> bottomLeft, ref int columnWeights, int rowWeight)
+            => PredictPaeth(top, left, topLeft);
+
+        /// <summary>
+        /// Selects the nearest Paeth reference for sixteen 8-bit lanes.
+        /// </summary>
+        /// <param name="top">The top candidates.</param>
+        /// <param name="left">The left candidates.</param>
+        /// <param name="topLeft">The top-left candidates.</param>
+        /// <returns>The selected candidates.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector128<byte> PredictPaeth(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft)
+        {
+            // The Paeth distances to left and top simplify to |top - topLeft| and |left - topLeft|. The established
+            // PNG predictor uses the same byte-lane identity, avoiding four widening stages for every sixteen samples.
+            Vector128<byte> topMinusTopLeft = Vector128.SubtractSaturate(top, topLeft);
+            Vector128<byte> leftMinusTopLeft = Vector128.SubtractSaturate(left, topLeft);
+            Vector128<byte> distanceLeft = Vector128.SubtractSaturate(topLeft, top) | topMinusTopLeft;
+            Vector128<byte> distanceTop = Vector128.SubtractSaturate(topLeft, left) | leftMinusTopLeft;
+            Vector128<byte> sameDirection = Vector128.Equals(Vector128.Equals(topMinusTopLeft, Vector128<byte>.Zero), Vector128.Equals(leftMinusTopLeft, Vector128<byte>.Zero));
+            Vector128<byte> distanceTopLeft = sameDirection | Vector128.SubtractSaturate(distanceTop, distanceLeft) | Vector128.SubtractSaturate(distanceLeft, distanceTop);
+            Vector128<byte> minimumTopTopLeft = Vector128.Min(distanceTopLeft, distanceTop);
+            Vector128<byte> topOrTopLeft = Vector128.ConditionalSelect(Vector128.Equals(minimumTopTopLeft, distanceTop), top, topLeft);
+            return Vector128.ConditionalSelect(Vector128.Equals(Vector128.Min(minimumTopTopLeft, distanceLeft), distanceLeft), left, topOrTopLeft);
+        }
+
+        /// <summary>
+        /// Selects the nearest Paeth reference for thirty-two 8-bit lanes.
+        /// </summary>
+        /// <param name="top">The top candidates.</param>
+        /// <param name="left">The left candidates.</param>
+        /// <param name="topLeft">The top-left candidates.</param>
+        /// <returns>The selected candidates.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector256<byte> PredictPaeth(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft)
+        {
+            Vector256<byte> topMinusTopLeft = Vector256.SubtractSaturate(top, topLeft);
+            Vector256<byte> leftMinusTopLeft = Vector256.SubtractSaturate(left, topLeft);
+            Vector256<byte> distanceLeft = Vector256.SubtractSaturate(topLeft, top) | topMinusTopLeft;
+            Vector256<byte> distanceTop = Vector256.SubtractSaturate(topLeft, left) | leftMinusTopLeft;
+            Vector256<byte> sameDirection = Vector256.Equals(Vector256.Equals(topMinusTopLeft, Vector256<byte>.Zero), Vector256.Equals(leftMinusTopLeft, Vector256<byte>.Zero));
+            Vector256<byte> distanceTopLeft = sameDirection | Vector256.SubtractSaturate(distanceTop, distanceLeft) | Vector256.SubtractSaturate(distanceLeft, distanceTop);
+            Vector256<byte> minimumTopTopLeft = Vector256.Min(distanceTopLeft, distanceTop);
+            Vector256<byte> topOrTopLeft = Vector256.ConditionalSelect(Vector256.Equals(minimumTopTopLeft, distanceTop), top, topLeft);
+            return Vector256.ConditionalSelect(Vector256.Equals(Vector256.Min(minimumTopTopLeft, distanceLeft), distanceLeft), left, topOrTopLeft);
+        }
+
+        /// <summary>
+        /// Selects the nearest Paeth reference for sixty-four 8-bit lanes.
+        /// </summary>
+        /// <param name="top">The top candidates.</param>
+        /// <param name="left">The left candidates.</param>
+        /// <param name="topLeft">The top-left candidates.</param>
+        /// <returns>The selected candidates.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector512<byte> PredictPaeth(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft)
+        {
+            Vector512<byte> topMinusTopLeft = Vector512.SubtractSaturate(top, topLeft);
+            Vector512<byte> leftMinusTopLeft = Vector512.SubtractSaturate(left, topLeft);
+            Vector512<byte> distanceLeft = Vector512.SubtractSaturate(topLeft, top) | topMinusTopLeft;
+            Vector512<byte> distanceTop = Vector512.SubtractSaturate(topLeft, left) | leftMinusTopLeft;
+            Vector512<byte> sameDirection = Vector512.Equals(Vector512.Equals(topMinusTopLeft, Vector512<byte>.Zero), Vector512.Equals(leftMinusTopLeft, Vector512<byte>.Zero));
+            Vector512<byte> distanceTopLeft = sameDirection | Vector512.SubtractSaturate(distanceTop, distanceLeft) | Vector512.SubtractSaturate(distanceLeft, distanceTop);
+            Vector512<byte> minimumTopTopLeft = Vector512.Min(distanceTopLeft, distanceTop);
+            Vector512<byte> topOrTopLeft = Vector512.ConditionalSelect(Vector512.Equals(minimumTopTopLeft, distanceTop), top, topLeft);
+            return Vector512.ConditionalSelect(Vector512.Equals(Vector512.Min(minimumTopTopLeft, distanceLeft), distanceLeft), left, topOrTopLeft);
+        }
+
+        /// <summary>
+        /// Selects the nearest Paeth reference for eight high-bit-depth lanes.
+        /// </summary>
+        /// <param name="top">The top candidates.</param>
+        /// <param name="left">The left candidates.</param>
+        /// <param name="topLeft">The top-left candidates.</param>
+        /// <returns>The selected candidates.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector128<short> PredictPaeth(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft)
+        {
+            // AV1 samples are at most twelve bits. Both signed differences and their sum are therefore bounded by
+            // 8190, allowing the exact Paeth distances to stay in signed 16-bit lanes without widening.
+            Vector128<short> topDelta = top - topLeft;
+            Vector128<short> leftDelta = left - topLeft;
+            Vector128<short> distanceLeft = Vector128.Abs(topDelta);
+            Vector128<short> distanceTop = Vector128.Abs(leftDelta);
+            Vector128<short> distanceTopLeft = Vector128.Abs(topDelta + leftDelta);
+
+            Vector128<short> minimumTopTopLeft = Vector128.Min(distanceTopLeft, distanceTop);
+            Vector128<short> topOrTopLeft = Vector128.ConditionalSelect(Vector128.Equals(minimumTopTopLeft, distanceTop), top, topLeft);
+            return Vector128.ConditionalSelect(Vector128.Equals(Vector128.Min(minimumTopTopLeft, distanceLeft), distanceLeft), left, topOrTopLeft);
+        }
+
+        /// <summary>
+        /// Selects the nearest Paeth reference for sixteen high-bit-depth lanes.
+        /// </summary>
+        /// <param name="top">The top candidates.</param>
+        /// <param name="left">The left candidates.</param>
+        /// <param name="topLeft">The top-left candidates.</param>
+        /// <returns>The selected candidates.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector256<short> PredictPaeth(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft)
+        {
+            Vector256<short> topDelta = top - topLeft;
+            Vector256<short> leftDelta = left - topLeft;
+            Vector256<short> distanceLeft = Vector256.Abs(topDelta);
+            Vector256<short> distanceTop = Vector256.Abs(leftDelta);
+            Vector256<short> distanceTopLeft = Vector256.Abs(topDelta + leftDelta);
+
+            Vector256<short> minimumTopTopLeft = Vector256.Min(distanceTopLeft, distanceTop);
+            Vector256<short> topOrTopLeft = Vector256.ConditionalSelect(Vector256.Equals(minimumTopTopLeft, distanceTop), top, topLeft);
+            return Vector256.ConditionalSelect(Vector256.Equals(Vector256.Min(minimumTopTopLeft, distanceLeft), distanceLeft), left, topOrTopLeft);
+        }
+
+        /// <summary>
+        /// Selects the nearest Paeth reference for thirty-two high-bit-depth lanes.
+        /// </summary>
+        /// <param name="top">The top candidates.</param>
+        /// <param name="left">The left candidates.</param>
+        /// <param name="topLeft">The top-left candidates.</param>
+        /// <returns>The selected candidates.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector512<short> PredictPaeth(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft)
+        {
+            Vector512<short> topDelta = top - topLeft;
+            Vector512<short> leftDelta = left - topLeft;
+            Vector512<short> distanceLeft = Vector512.Abs(topDelta);
+            Vector512<short> distanceTop = Vector512.Abs(leftDelta);
+            Vector512<short> distanceTopLeft = Vector512.Abs(topDelta + leftDelta);
+
+            Vector512<short> minimumTopTopLeft = Vector512.Min(distanceTopLeft, distanceTop);
+            Vector512<short> topOrTopLeft = Vector512.ConditionalSelect(Vector512.Equals(minimumTopTopLeft, distanceTop), top, topLeft);
+            return Vector512.ConditionalSelect(Vector512.Equals(Vector512.Min(minimumTopTopLeft, distanceLeft), distanceLeft), left, topOrTopLeft);
+        }
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.SmoothHorizontalOperator.cs

@@ -0,0 +1,161 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Implements horizontal AV1 smooth intra prediction for scalar and SIMD lanes.
+    /// </summary>
+    internal readonly struct SmoothHorizontalOperator : IAv1IntraPredictionOperator
+    {
+        /// <summary>
+        /// The Q8 scale used by the smooth surface.
+        /// </summary>
+        private const int WeightScale = 256;
+
+        /// <inheritdoc/>
+        public static Av1PredictionMode Mode => Av1PredictionMode.SmoothHorizontal;
+
+        /// <inheritdoc/>
+        public static Av1IntraPredictionInputs Inputs
+            => Av1IntraPredictionInputs.Left | Av1IntraPredictionInputs.TopRight | Av1IntraPredictionInputs.ColumnWeight;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte Predict(byte top, byte left, byte topLeft, byte topRight, byte bottomLeft, int columnWeight, int rowWeight)
+            => (byte)(((left * columnWeight) + (topRight * (WeightScale - columnWeight)) + (WeightScale >> 1)) >> 8);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<byte> Predict(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft, Vector128<byte> topRight, Vector128<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector128<int> endpointBias = Vector128.Create((topRightSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(Vector128.LoadUnsafe(ref columnWeights), horizontalDelta, endpointBias),
+                Calculate(Vector128.LoadUnsafe(ref columnWeights, (nuint)Vector128<int>.Count), horizontalDelta, endpointBias),
+                Calculate(Vector128.LoadUnsafe(ref columnWeights, (nuint)(2 * Vector128<int>.Count)), horizontalDelta, endpointBias),
+                Calculate(Vector128.LoadUnsafe(ref columnWeights, (nuint)(3 * Vector128<int>.Count)), horizontalDelta, endpointBias));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<byte> Predict(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft, Vector256<byte> topRight, Vector256<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector256<int> endpointBias = Vector256.Create((topRightSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(Vector256.LoadUnsafe(ref columnWeights), horizontalDelta, endpointBias),
+                Calculate(Vector256.LoadUnsafe(ref columnWeights, (nuint)Vector256<int>.Count), horizontalDelta, endpointBias),
+                Calculate(Vector256.LoadUnsafe(ref columnWeights, (nuint)(2 * Vector256<int>.Count)), horizontalDelta, endpointBias),
+                Calculate(Vector256.LoadUnsafe(ref columnWeights, (nuint)(3 * Vector256<int>.Count)), horizontalDelta, endpointBias));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<byte> Predict(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft, Vector512<byte> topRight, Vector512<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector512<int> endpointBias = Vector512.Create((topRightSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(Vector512.LoadUnsafe(ref columnWeights), horizontalDelta, endpointBias),
+                Calculate(Vector512.LoadUnsafe(ref columnWeights, (nuint)Vector512<int>.Count), horizontalDelta, endpointBias),
+                Calculate(Vector512.LoadUnsafe(ref columnWeights, (nuint)(2 * Vector512<int>.Count)), horizontalDelta, endpointBias),
+                Calculate(Vector512.LoadUnsafe(ref columnWeights, (nuint)(3 * Vector512<int>.Count)), horizontalDelta, endpointBias));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Predict(short top, short left, short topLeft, short topRight, short bottomLeft, int columnWeight, int rowWeight)
+            => (short)(((left * columnWeight) + (topRight * (WeightScale - columnWeight)) + (WeightScale >> 1)) >> 8);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> Predict(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft, Vector128<short> topRight, Vector128<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector128<int> endpointBias = Vector128.Create((topRightSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(Vector128.LoadUnsafe(ref columnWeights), horizontalDelta, endpointBias),
+                Calculate(Vector128.LoadUnsafe(ref columnWeights, (nuint)Vector128<int>.Count), horizontalDelta, endpointBias));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<short> Predict(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft, Vector256<short> topRight, Vector256<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector256<int> endpointBias = Vector256.Create((topRightSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(Vector256.LoadUnsafe(ref columnWeights), horizontalDelta, endpointBias),
+                Calculate(Vector256.LoadUnsafe(ref columnWeights, (nuint)Vector256<int>.Count), horizontalDelta, endpointBias));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<short> Predict(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft, Vector512<short> topRight, Vector512<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector512<int> endpointBias = Vector512.Create((topRightSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(Vector512.LoadUnsafe(ref columnWeights), horizontalDelta, endpointBias),
+                Calculate(Vector512.LoadUnsafe(ref columnWeights, (nuint)Vector512<int>.Count), horizontalDelta, endpointBias));
+        }
+
+        /// <summary>
+        /// Calculates four horizontal smooth predictions.
+        /// </summary>
+        /// <param name="columnWeights">The horizontal Q8 weights.</param>
+        /// <param name="horizontalDelta">The difference between the left sample and top-right endpoint.</param>
+        /// <param name="endpointBias">The top-right endpoint and rounding bias in every lane.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector128<int> Calculate(Vector128<int> columnWeights, int horizontalDelta, Vector128<int> endpointBias)
+            => ((columnWeights * horizontalDelta) + endpointBias) >> 8;
+
+        /// <summary>
+        /// Calculates eight horizontal smooth predictions.
+        /// </summary>
+        /// <param name="columnWeights">The horizontal Q8 weights.</param>
+        /// <param name="horizontalDelta">The difference between the left sample and top-right endpoint.</param>
+        /// <param name="endpointBias">The top-right endpoint and rounding bias in every lane.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector256<int> Calculate(Vector256<int> columnWeights, int horizontalDelta, Vector256<int> endpointBias)
+            => ((columnWeights * horizontalDelta) + endpointBias) >> 8;
+
+        /// <summary>
+        /// Calculates sixteen horizontal smooth predictions.
+        /// </summary>
+        /// <param name="columnWeights">The horizontal Q8 weights.</param>
+        /// <param name="horizontalDelta">The difference between the left sample and top-right endpoint.</param>
+        /// <param name="endpointBias">The top-right endpoint and rounding bias in every lane.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector512<int> Calculate(Vector512<int> columnWeights, int horizontalDelta, Vector512<int> endpointBias)
+            => ((columnWeights * horizontalDelta) + endpointBias) >> 8;
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.SmoothOperator.cs

@@ -0,0 +1,241 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Implements two-dimensional AV1 smooth intra prediction for scalar and SIMD lanes.
+    /// </summary>
+    internal readonly struct SmoothOperator : IAv1IntraPredictionOperator
+    {
+        /// <summary>
+        /// The Q8 scale used by each smooth surface.
+        /// </summary>
+        private const int WeightScale = 256;
+
+        /// <inheritdoc/>
+        public static Av1PredictionMode Mode => Av1PredictionMode.Smooth;
+
+        /// <inheritdoc/>
+        public static Av1IntraPredictionInputs Inputs
+            => Av1IntraPredictionInputs.Top
+            | Av1IntraPredictionInputs.Left
+            | Av1IntraPredictionInputs.TopRight
+            | Av1IntraPredictionInputs.BottomLeft
+            | Av1IntraPredictionInputs.ColumnWeight
+            | Av1IntraPredictionInputs.RowWeight;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte Predict(byte top, byte left, byte topLeft, byte topRight, byte bottomLeft, int columnWeight, int rowWeight)
+        {
+            int prediction = (top * rowWeight) + (bottomLeft * (WeightScale - rowWeight));
+            prediction += (left * columnWeight) + (topRight * (WeightScale - columnWeight));
+            return (byte)((prediction + WeightScale) >> 9);
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<byte> Predict(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft, Vector128<byte> topRight, Vector128<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector128<int> top0, out Vector128<int> top1, out Vector128<int> top2, out Vector128<int> top3);
+            Vector128<int> weight0 = Vector128.LoadUnsafe(ref columnWeights);
+            Vector128<int> weight1 = Vector128.LoadUnsafe(ref columnWeights, (nuint)Vector128<int>.Count);
+            Vector128<int> weight2 = Vector128.LoadUnsafe(ref columnWeights, (nuint)(2 * Vector128<int>.Count));
+            Vector128<int> weight3 = Vector128.LoadUnsafe(ref columnWeights, (nuint)(3 * Vector128<int>.Count));
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector128<int> bottomLeftVector = Vector128.Create(bottomLeftSample);
+            Vector128<int> endpointBias = Vector128.Create(((bottomLeftSample + topRightSample) * WeightScale) + WeightScale);
+
+            return Narrow(
+                Calculate(top0, weight0, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top1, weight1, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top2, weight2, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top3, weight3, bottomLeftVector, horizontalDelta, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<byte> Predict(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft, Vector256<byte> topRight, Vector256<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector256<int> top0, out Vector256<int> top1, out Vector256<int> top2, out Vector256<int> top3);
+            Vector256<int> weight0 = Vector256.LoadUnsafe(ref columnWeights);
+            Vector256<int> weight1 = Vector256.LoadUnsafe(ref columnWeights, (nuint)Vector256<int>.Count);
+            Vector256<int> weight2 = Vector256.LoadUnsafe(ref columnWeights, (nuint)(2 * Vector256<int>.Count));
+            Vector256<int> weight3 = Vector256.LoadUnsafe(ref columnWeights, (nuint)(3 * Vector256<int>.Count));
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector256<int> bottomLeftVector = Vector256.Create(bottomLeftSample);
+            Vector256<int> endpointBias = Vector256.Create(((bottomLeftSample + topRightSample) * WeightScale) + WeightScale);
+
+            return Narrow(
+                Calculate(top0, weight0, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top1, weight1, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top2, weight2, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top3, weight3, bottomLeftVector, horizontalDelta, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<byte> Predict(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft, Vector512<byte> topRight, Vector512<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector512<int> top0, out Vector512<int> top1, out Vector512<int> top2, out Vector512<int> top3);
+            Vector512<int> weight0 = Vector512.LoadUnsafe(ref columnWeights);
+            Vector512<int> weight1 = Vector512.LoadUnsafe(ref columnWeights, (nuint)Vector512<int>.Count);
+            Vector512<int> weight2 = Vector512.LoadUnsafe(ref columnWeights, (nuint)(2 * Vector512<int>.Count));
+            Vector512<int> weight3 = Vector512.LoadUnsafe(ref columnWeights, (nuint)(3 * Vector512<int>.Count));
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector512<int> bottomLeftVector = Vector512.Create(bottomLeftSample);
+            Vector512<int> endpointBias = Vector512.Create(((bottomLeftSample + topRightSample) * WeightScale) + WeightScale);
+
+            return Narrow(
+                Calculate(top0, weight0, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top1, weight1, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top2, weight2, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top3, weight3, bottomLeftVector, horizontalDelta, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Predict(short top, short left, short topLeft, short topRight, short bottomLeft, int columnWeight, int rowWeight)
+        {
+            int prediction = (top * rowWeight) + (bottomLeft * (WeightScale - rowWeight));
+            prediction += (left * columnWeight) + (topRight * (WeightScale - columnWeight));
+            return (short)((prediction + WeightScale) >> 9);
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> Predict(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft, Vector128<short> topRight, Vector128<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector128<int> top0, out Vector128<int> top1);
+            Vector128<int> weight0 = Vector128.LoadUnsafe(ref columnWeights);
+            Vector128<int> weight1 = Vector128.LoadUnsafe(ref columnWeights, (nuint)Vector128<int>.Count);
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector128<int> bottomLeftVector = Vector128.Create(bottomLeftSample);
+            Vector128<int> endpointBias = Vector128.Create(((bottomLeftSample + topRightSample) * WeightScale) + WeightScale);
+
+            return Narrow(
+                Calculate(top0, weight0, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top1, weight1, bottomLeftVector, horizontalDelta, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<short> Predict(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft, Vector256<short> topRight, Vector256<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector256<int> top0, out Vector256<int> top1);
+            Vector256<int> weight0 = Vector256.LoadUnsafe(ref columnWeights);
+            Vector256<int> weight1 = Vector256.LoadUnsafe(ref columnWeights, (nuint)Vector256<int>.Count);
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector256<int> bottomLeftVector = Vector256.Create(bottomLeftSample);
+            Vector256<int> endpointBias = Vector256.Create(((bottomLeftSample + topRightSample) * WeightScale) + WeightScale);
+
+            return Narrow(
+                Calculate(top0, weight0, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top1, weight1, bottomLeftVector, horizontalDelta, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<short> Predict(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft, Vector512<short> topRight, Vector512<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector512<int> top0, out Vector512<int> top1);
+            Vector512<int> weight0 = Vector512.LoadUnsafe(ref columnWeights);
+            Vector512<int> weight1 = Vector512.LoadUnsafe(ref columnWeights, (nuint)Vector512<int>.Count);
+            int leftSample = left.GetElement(0);
+            int topRightSample = topRight.GetElement(0);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            int horizontalDelta = leftSample - topRightSample;
+            Vector512<int> bottomLeftVector = Vector512.Create(bottomLeftSample);
+            Vector512<int> endpointBias = Vector512.Create(((bottomLeftSample + topRightSample) * WeightScale) + WeightScale);
+
+            return Narrow(
+                Calculate(top0, weight0, bottomLeftVector, horizontalDelta, endpointBias, rowWeight),
+                Calculate(top1, weight1, bottomLeftVector, horizontalDelta, endpointBias, rowWeight));
+        }
+
+        /// <summary>
+        /// Calculates four two-dimensional smooth predictions.
+        /// </summary>
+        /// <param name="top">The widened top samples.</param>
+        /// <param name="columnWeights">The horizontal Q8 weights.</param>
+        /// <param name="bottomLeft">The bottom-left endpoint in every lane.</param>
+        /// <param name="horizontalDelta">The difference between the left sample and top-right endpoint.</param>
+        /// <param name="endpointBias">The combined endpoint and rounding bias in every lane.</param>
+        /// <param name="rowWeight">The vertical Q8 weight.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector128<int> Calculate(
+            Vector128<int> top,
+            Vector128<int> columnWeights,
+            Vector128<int> bottomLeft,
+            int horizontalDelta,
+            Vector128<int> endpointBias,
+            int rowWeight)
+        {
+            // Expanding the complementary weights gives the exact normative sum while reducing it to two vector
+            // multiplications: (top - bottom) * rowWeight + (left - right) * columnWeight + the endpoint bias.
+            return (((top - bottomLeft) * rowWeight) + (columnWeights * horizontalDelta) + endpointBias) >> 9;
+        }
+
+        /// <summary>
+        /// Calculates eight two-dimensional smooth predictions.
+        /// </summary>
+        /// <param name="top">The widened top samples.</param>
+        /// <param name="columnWeights">The horizontal Q8 weights.</param>
+        /// <param name="bottomLeft">The bottom-left endpoint in every lane.</param>
+        /// <param name="horizontalDelta">The difference between the left sample and top-right endpoint.</param>
+        /// <param name="endpointBias">The combined endpoint and rounding bias in every lane.</param>
+        /// <param name="rowWeight">The vertical Q8 weight.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector256<int> Calculate(
+            Vector256<int> top,
+            Vector256<int> columnWeights,
+            Vector256<int> bottomLeft,
+            int horizontalDelta,
+            Vector256<int> endpointBias,
+            int rowWeight)
+            => (((top - bottomLeft) * rowWeight) + (columnWeights * horizontalDelta) + endpointBias) >> 9;
+
+        /// <summary>
+        /// Calculates sixteen two-dimensional smooth predictions.
+        /// </summary>
+        /// <param name="top">The widened top samples.</param>
+        /// <param name="columnWeights">The horizontal Q8 weights.</param>
+        /// <param name="bottomLeft">The bottom-left endpoint in every lane.</param>
+        /// <param name="horizontalDelta">The difference between the left sample and top-right endpoint.</param>
+        /// <param name="endpointBias">The combined endpoint and rounding bias in every lane.</param>
+        /// <param name="rowWeight">The vertical Q8 weight.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector512<int> Calculate(
+            Vector512<int> top,
+            Vector512<int> columnWeights,
+            Vector512<int> bottomLeft,
+            int horizontalDelta,
+            Vector512<int> endpointBias,
+            int rowWeight)
+            => (((top - bottomLeft) * rowWeight) + (columnWeights * horizontalDelta) + endpointBias) >> 9;
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.SmoothVerticalOperator.cs

@@ -0,0 +1,164 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Implements vertical AV1 smooth intra prediction for scalar and SIMD lanes.
+    /// </summary>
+    internal readonly struct SmoothVerticalOperator : IAv1IntraPredictionOperator
+    {
+        /// <summary>
+        /// The Q8 scale used by the smooth surface.
+        /// </summary>
+        private const int WeightScale = 256;
+
+        /// <inheritdoc/>
+        public static Av1PredictionMode Mode => Av1PredictionMode.SmoothVertical;
+
+        /// <inheritdoc/>
+        public static Av1IntraPredictionInputs Inputs
+            => Av1IntraPredictionInputs.Top | Av1IntraPredictionInputs.BottomLeft | Av1IntraPredictionInputs.RowWeight;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte Predict(byte top, byte left, byte topLeft, byte topRight, byte bottomLeft, int columnWeight, int rowWeight)
+            => (byte)(((top * rowWeight) + (bottomLeft * (WeightScale - rowWeight)) + (WeightScale >> 1)) >> 8);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<byte> Predict(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft, Vector128<byte> topRight, Vector128<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector128<int> top0, out Vector128<int> top1, out Vector128<int> top2, out Vector128<int> top3);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            Vector128<int> bottomLeftVector = Vector128.Create(bottomLeftSample);
+            Vector128<int> endpointBias = Vector128.Create((bottomLeftSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(top0, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top1, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top2, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top3, bottomLeftVector, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<byte> Predict(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft, Vector256<byte> topRight, Vector256<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector256<int> top0, out Vector256<int> top1, out Vector256<int> top2, out Vector256<int> top3);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            Vector256<int> bottomLeftVector = Vector256.Create(bottomLeftSample);
+            Vector256<int> endpointBias = Vector256.Create((bottomLeftSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(top0, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top1, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top2, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top3, bottomLeftVector, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<byte> Predict(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft, Vector512<byte> topRight, Vector512<byte> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector512<int> top0, out Vector512<int> top1, out Vector512<int> top2, out Vector512<int> top3);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            Vector512<int> bottomLeftVector = Vector512.Create(bottomLeftSample);
+            Vector512<int> endpointBias = Vector512.Create((bottomLeftSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(top0, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top1, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top2, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top3, bottomLeftVector, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Predict(short top, short left, short topLeft, short topRight, short bottomLeft, int columnWeight, int rowWeight)
+            => (short)(((top * rowWeight) + (bottomLeft * (WeightScale - rowWeight)) + (WeightScale >> 1)) >> 8);
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> Predict(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft, Vector128<short> topRight, Vector128<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector128<int> top0, out Vector128<int> top1);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            Vector128<int> bottomLeftVector = Vector128.Create(bottomLeftSample);
+            Vector128<int> endpointBias = Vector128.Create((bottomLeftSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(top0, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top1, bottomLeftVector, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<short> Predict(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft, Vector256<short> topRight, Vector256<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector256<int> top0, out Vector256<int> top1);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            Vector256<int> bottomLeftVector = Vector256.Create(bottomLeftSample);
+            Vector256<int> endpointBias = Vector256.Create((bottomLeftSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(top0, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top1, bottomLeftVector, endpointBias, rowWeight));
+        }
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<short> Predict(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft, Vector512<short> topRight, Vector512<short> bottomLeft, ref int columnWeights, int rowWeight)
+        {
+            Widen(top, out Vector512<int> top0, out Vector512<int> top1);
+            int bottomLeftSample = bottomLeft.GetElement(0);
+            Vector512<int> bottomLeftVector = Vector512.Create(bottomLeftSample);
+            Vector512<int> endpointBias = Vector512.Create((bottomLeftSample * WeightScale) + (WeightScale >> 1));
+
+            return Narrow(
+                Calculate(top0, bottomLeftVector, endpointBias, rowWeight),
+                Calculate(top1, bottomLeftVector, endpointBias, rowWeight));
+        }
+
+        /// <summary>
+        /// Calculates four vertical smooth predictions.
+        /// </summary>
+        /// <param name="top">The widened top samples.</param>
+        /// <param name="bottomLeft">The bottom-left endpoint in every lane.</param>
+        /// <param name="endpointBias">The bottom-left endpoint and rounding bias in every lane.</param>
+        /// <param name="rowWeight">The vertical Q8 weight.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector128<int> Calculate(Vector128<int> top, Vector128<int> bottomLeft, Vector128<int> endpointBias, int rowWeight)
+            => (((top - bottomLeft) * rowWeight) + endpointBias) >> 8;
+
+        /// <summary>
+        /// Calculates eight vertical smooth predictions.
+        /// </summary>
+        /// <param name="top">The widened top samples.</param>
+        /// <param name="bottomLeft">The bottom-left endpoint in every lane.</param>
+        /// <param name="endpointBias">The bottom-left endpoint and rounding bias in every lane.</param>
+        /// <param name="rowWeight">The vertical Q8 weight.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector256<int> Calculate(Vector256<int> top, Vector256<int> bottomLeft, Vector256<int> endpointBias, int rowWeight)
+            => (((top - bottomLeft) * rowWeight) + endpointBias) >> 8;
+
+        /// <summary>
+        /// Calculates sixteen vertical smooth predictions.
+        /// </summary>
+        /// <param name="top">The widened top samples.</param>
+        /// <param name="bottomLeft">The bottom-left endpoint in every lane.</param>
+        /// <param name="endpointBias">The bottom-left endpoint and rounding bias in every lane.</param>
+        /// <param name="rowWeight">The vertical Q8 weight.</param>
+        /// <returns>The rounded predictions.</returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private static Vector512<int> Calculate(Vector512<int> top, Vector512<int> bottomLeft, Vector512<int> endpointBias, int rowWeight)
+            => (((top - bottomLeft) * rowWeight) + endpointBias) >> 8;
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictor.VerticalOperator.cs

@@ -0,0 +1,54 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+using System.Runtime.CompilerServices;
+using System.Runtime.Intrinsics;
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// Implements AV1 vertical intra prediction for scalar and SIMD lanes.
+    /// </summary>
+    internal readonly struct VerticalOperator : IAv1IntraPredictionOperator
+    {
+        /// <inheritdoc/>
+        public static Av1PredictionMode Mode => Av1PredictionMode.Vertical;
+
+        /// <inheritdoc/>
+        public static Av1IntraPredictionInputs Inputs => Av1IntraPredictionInputs.Top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static byte Predict(byte top, byte left, byte topLeft, byte topRight, byte bottomLeft, int columnWeight, int rowWeight) => top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<byte> Predict(Vector128<byte> top, Vector128<byte> left, Vector128<byte> topLeft, Vector128<byte> topRight, Vector128<byte> bottomLeft, ref int columnWeights, int rowWeight) => top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<byte> Predict(Vector256<byte> top, Vector256<byte> left, Vector256<byte> topLeft, Vector256<byte> topRight, Vector256<byte> bottomLeft, ref int columnWeights, int rowWeight) => top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<byte> Predict(Vector512<byte> top, Vector512<byte> left, Vector512<byte> topLeft, Vector512<byte> topRight, Vector512<byte> bottomLeft, ref int columnWeights, int rowWeight) => top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static short Predict(short top, short left, short topLeft, short topRight, short bottomLeft, int columnWeight, int rowWeight) => top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector128<short> Predict(Vector128<short> top, Vector128<short> left, Vector128<short> topLeft, Vector128<short> topRight, Vector128<short> bottomLeft, ref int columnWeights, int rowWeight) => top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector256<short> Predict(Vector256<short> top, Vector256<short> left, Vector256<short> topLeft, Vector256<short> topRight, Vector256<short> bottomLeft, ref int columnWeights, int rowWeight) => top;
+
+        /// <inheritdoc/>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static Vector512<short> Predict(Vector512<short> top, Vector512<short> left, Vector512<short> topLeft, Vector512<short> topRight, Vector512<short> bottomLeft, ref int columnWeights, int rowWeight) => top;
+    }
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1IntraPredictorBase.cs

@@ -0,0 +1,129 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
+
+/// <summary>
+/// Reconstructs non-directional AV1 intra-prediction blocks from prepared neighboring samples.
+/// </summary>
+/// <remarks>
+/// The implementation covers the non-directional prediction processes in section 7.11.2 of the AV1 specification.
+/// </remarks>
+internal abstract partial class Av1IntraPredictorBase
+{
+    /// <summary>
+    /// The horizontal prediction operator.
+    /// </summary>
+    private static readonly Av1IntraPredictor<HorizontalOperator> HorizontalPredictor = new();
+
+    /// <summary>
+    /// The vertical prediction operator.
+    /// </summary>
+    private static readonly Av1IntraPredictor<VerticalOperator> VerticalPredictor = new();
+
+    /// <summary>
+    /// The Paeth prediction operator.
+    /// </summary>
+    private static readonly Av1IntraPredictor<PaethOperator> PaethPredictor = new();
+
+    /// <summary>
+    /// The two-dimensional smooth prediction operator.
+    /// </summary>
+    private static readonly Av1IntraPredictor<SmoothOperator> SmoothPredictor = new();
+
+    /// <summary>
+    /// The horizontal smooth prediction operator.
+    /// </summary>
+    private static readonly Av1IntraPredictor<SmoothHorizontalOperator> SmoothHorizontalPredictor = new();
+
+    /// <summary>
+    /// The vertical smooth prediction operator.
+    /// </summary>
+    private static readonly Av1IntraPredictor<SmoothVerticalOperator> SmoothVerticalPredictor = new();
+
+    /// <summary>
+    /// Gets the Q8 smooth weights for every supported block dimension.
+    /// </summary>
+    private static ReadOnlySpan<int> SmoothWeights =>
+    [
+
+        // The first two entries are unused because the smallest AV1 prediction dimension is four samples.
+        0, 0,
+        255, 128,
+        255, 149, 85, 64,
+        255, 197, 146, 105, 73, 50, 37, 32,
+        255, 225, 196, 170, 145, 123, 102, 84, 68, 54, 43, 33, 26, 20, 17, 16,
+        255, 240, 225, 210, 196, 182, 169, 157, 145, 133, 122, 111, 101, 92, 83, 74,
+        66, 59, 52, 45, 39, 34, 29, 25, 21, 17, 14, 12, 10, 9, 8, 8,
+        255, 248, 240, 233, 225, 218, 210, 203, 196, 189, 182, 176, 169, 163, 156,
+        150, 144, 138, 133, 127, 121, 116, 111, 106, 101, 96, 91, 86, 82, 77, 73, 69,
+        65, 61, 57, 54, 50, 47, 44, 41, 38, 35, 32, 29, 27, 25, 22, 20, 18, 16, 15,
+        13, 12, 10, 9, 8, 7, 6, 6, 5, 5, 4, 4, 4,
+    ];
+
+    /// <summary>
+    /// Gets the prediction mode implemented by this predictor.
+    /// </summary>
+    public abstract Av1PredictionMode Mode { get; }
+
+    /// <summary>
+    /// Gets the closed predictor for a non-directional AV1 prediction mode.
+    /// </summary>
+    /// <param name="mode">The decoded non-directional prediction mode.</param>
+    /// <returns>The predictor for <paramref name="mode"/>.</returns>
+    public static Av1IntraPredictorBase GetPredictor(Av1PredictionMode mode)
+        => mode switch
+        {
+            Av1PredictionMode.Horizontal => HorizontalPredictor,
+            Av1PredictionMode.Vertical => VerticalPredictor,
+            Av1PredictionMode.Paeth => PaethPredictor,
+            Av1PredictionMode.Smooth => SmoothPredictor,
+            Av1PredictionMode.SmoothHorizontal => SmoothHorizontalPredictor,
+            Av1PredictionMode.SmoothVertical => SmoothVerticalPredictor,
+            _ => throw new InvalidImageContentException($"Prediction mode {mode} is not a non-directional AV1 mode."),
+        };
+
+    /// <summary>
+    /// Predicts an 8-bit block.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    public abstract void Predict(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height);
+
+    /// <summary>
+    /// Predicts a high-bit-depth block.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    public abstract void Predict(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height);
+
+    /// <summary>
+    /// Predicts an 8-bit block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    public abstract void PredictScalar(Span<byte> destination, int destinationStride, ReadOnlySpan<byte> above, ReadOnlySpan<byte> left, int width, int height);
+
+    /// <summary>
+    /// Predicts a high-bit-depth block without hardware intrinsics.
+    /// </summary>
+    /// <param name="destination">The destination block origin.</param>
+    /// <param name="destinationStride">The destination row stride in samples.</param>
+    /// <param name="above">The prepared top reference, preceded in memory by the top-left sample.</param>
+    /// <param name="left">The prepared left reference.</param>
+    /// <param name="width">The block width in samples.</param>
+    /// <param name="height">The block height in samples.</param>
+    public abstract void PredictScalar(Span<short> destination, int destinationStride, ReadOnlySpan<short> above, ReadOnlySpan<short> left, int width, int height);
+}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1PaethPredictor.cs

@@ -1,99 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block by selecting the top, left, or top-left neighbor with the smallest local gradient.
-/// </summary>
-internal readonly struct Av1PaethPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of top samples consumed and samples written to each destination row.
-    /// </summary>
-    private readonly uint blockWidth;
-
-    /// <summary>
-    /// The number of left samples consumed and destination rows written.
-    /// </summary>
-    private readonly uint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1PaethPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1PaethPredictor(Size blockSize)
-    {
-        this.blockWidth = (uint)blockSize.Width;
-        this.blockHeight = (uint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1PaethPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1PaethPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (uint)transformSize.GetWidth();
-        this.blockHeight = (uint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block using the Paeth gradient selector.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top neighboring samples, preceded in memory by the top-left sample.</param>
-    /// <param name="left">The left neighboring samples.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1PaethPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte leftRef = ref left[0];
-        ref byte aboveRef = ref above[0];
-
-        // The caller preserves the top-left sample immediately before the top row.
-        int yTopLeft = Unsafe.Subtract(ref aboveRef, 1);
-        ref byte destinationRef = ref destination[0];
-        for (nuint r = 0; r < this.blockHeight; r++)
-        {
-            for (nuint c = 0; c < this.blockWidth; c++)
-            {
-                Unsafe.Add(ref destinationRef, c) = PredictSingle(
-                    Unsafe.Add(ref leftRef, r),
-                    Unsafe.Add(ref aboveRef, c),
-                    yTopLeft);
-            }
-
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-
-    /// <summary>
-    /// Selects the reference sample nearest to the planar estimate <paramref name="top"/> + <paramref name="left"/> - <paramref name="topLeft"/>.
-    /// </summary>
-    /// <param name="left">The left reference sample.</param>
-    /// <param name="top">The top reference sample.</param>
-    /// <param name="topLeft">The shared top-left reference sample.</param>
-    /// <returns>The reference sample with the smallest absolute distance from the planar estimate.</returns>
-    private static byte PredictSingle(byte left, byte top, int topLeft)
-    {
-        int basis = top + left - topLeft;
-        int pLeft = Av1Math.AbsoluteDifference(basis, left);
-        int pTop = Av1Math.AbsoluteDifference(basis, top);
-        int pTopLeft = Av1Math.AbsoluteDifference(basis, topLeft);
-
-        // Ties prefer left, then top, matching AV1's normative Paeth selection order.
-        return (byte)((pLeft <= pTop && pLeft <= pTopLeft) ? left : (pTop <= pTopLeft) ? top : topLeft);
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1PredictionDecoder.cs

@@ -4,6 +4,8 @@
 using System.Numerics;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
+using System.Runtime.Intrinsics;
+using SixLabors.ImageSharp.Common.Helpers;
 using SixLabors.ImageSharp.Formats.Heif.Av1.OpenBitstreamUnit;
 using SixLabors.ImageSharp.Formats.Heif.Av1.Prediction.ChromaFromLuma;
 using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
@@ -24,6 +26,21 @@ internal class Av1PredictionDecoder
     /// </summary>
     private const int MaxUpsampleSize = 16;
 
+    /// <summary>
+    /// The number of samples reserved for one prepared AV1 intra-prediction edge.
+    /// </summary>
+    private const int ReferenceBufferLength = (Av1Constants.MaxTransformSize * 2) + 32;
+
+    /// <summary>
+    /// The padded sample count required by the widest intra-edge SIMD loads.
+    /// </summary>
+    private const int EdgeScratchLength = 160;
+
+    /// <summary>
+    /// The number of high-bit-depth samples required by the reusable prediction workspace.
+    /// </summary>
+    public const int ScratchLength = Av1DirectionalIntraPredictor.ScratchLength + (2 * ReferenceBufferLength) + EdgeScratchLength;
+
     /// <summary>
     /// The sequence-level syntax that controls chroma sampling, bit depth, superblock size, and intra-edge filtering.
     /// </summary>
@@ -34,15 +51,22 @@ internal class Av1PredictionDecoder
     /// </summary>
     private readonly ObuFrameHeader frameHeader;
 
+    /// <summary>
+    /// The frame-owned workspace shared by directional and filter-intra predictors.
+    /// </summary>
+    private readonly Memory<short> predictorScratch;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="Av1PredictionDecoder"/> class.
     /// </summary>
     /// <param name="sequenceHeader">The decoded sequence header for the current image.</param>
     /// <param name="frameHeader">The decoded frame header for the current image.</param>
-    public Av1PredictionDecoder(ObuSequenceHeader sequenceHeader, ObuFrameHeader frameHeader)
+    /// <param name="predictorScratch">The reusable predictor workspace owned by the containing block decoder.</param>
+    public Av1PredictionDecoder(ObuSequenceHeader sequenceHeader, ObuFrameHeader frameHeader, Memory<short> predictorScratch)
     {
         this.sequenceHeader = sequenceHeader;
         this.frameHeader = frameHeader;
+        this.predictorScratch = predictorScratch;
     }
 
     /// <summary>
@@ -791,10 +815,15 @@ internal class Av1PredictionDecoder
     {
         int baseValue = 128 << (bitDepth - 8);
 
+        // The frame-owned allocation is sized in high-bit-depth samples. Reinterpreting it as T gives the byte
+        // path additional capacity while preserving the same sample offsets for the larger short representation.
+        Span<T> scratch = MemoryMarshal.Cast<short, T>(this.predictorScratch.Span);
+        Span<T> aboveData = scratch.Slice(Av1DirectionalIntraPredictor.ScratchLength, ReferenceBufferLength);
+        Span<T> leftData = scratch.Slice(Av1DirectionalIntraPredictor.ScratchLength + ReferenceBufferLength, ReferenceBufferLength);
+        Span<T> edgeScratch = scratch.Slice(Av1DirectionalIntraPredictor.ScratchLength + (2 * ReferenceBufferLength), EdgeScratchLength);
+
         // Prefix storage is required because AV1 addresses the shared top-left sample at -1
         // and writes upsampled edge samples as far back as -2.
-        Span<T> aboveData = stackalloc T[(Av1Constants.MaxTransformSize * 2) + 32];
-        Span<T> leftData = stackalloc T[(Av1Constants.MaxTransformSize * 2) + 32];
         aboveData.Fill(T.CreateChecked(baseValue - 1));
         leftData.Fill(T.CreateChecked(baseValue + 1));
         Span<T> aboveRow = aboveData[16..];
@@ -989,7 +1018,7 @@ internal class Av1PredictionDecoder
 
         if (useFilterIntra)
         {
-            FilterIntraPredictor(destination, destinationStride, transformSize, aboveRow, leftColumn, filterIntraMode, bitDepth);
+            this.FilterIntraPredictor(destination, destinationStride, transformSize, aboveRow, leftColumn, filterIntraMode, bitDepth);
             return;
         }
 
@@ -1016,14 +1045,14 @@ internal class Av1PredictionDecoder
                     {
                         int strength = IntraEdgeFilterStrength(transformWidth, transformHeight, angle - 90, filterType);
                         int pixelCount = topPixelCount + ab_le + (needRight ? transformHeight : 0);
-                        FilterIntraEdge(ref Unsafe.Subtract(ref aboveRow[0], ab_le), pixelCount, strength);
+                        FilterIntraEdge(ref Unsafe.Subtract(ref aboveRow[0], ab_le), pixelCount, strength, edgeScratch);
                     }
 
                     if (needLeft && leftPixelCount > 0)
                     {
                         int strength = IntraEdgeFilterStrength(transformHeight, transformWidth, angle - 180, filterType);
                         int pixelCount = leftPixelCount + ab_le + (needBottom ? transformWidth : 0);
-                        FilterIntraEdge(ref Unsafe.Subtract(ref leftColumn[0], ab_le), pixelCount, strength);
+                        FilterIntraEdge(ref Unsafe.Subtract(ref leftColumn[0], ab_le), pixelCount, strength, edgeScratch);
                     }
                 }
 
@@ -1032,7 +1061,7 @@ internal class Av1PredictionDecoder
                 {
                     int pixelCount = transformWidth + (needRight ? transformHeight : 0);
 
-                    UpsampleIntraEdge(aboveRow, pixelCount, bitDepth);
+                    UpsampleIntraEdge(aboveRow, pixelCount, bitDepth, edgeScratch);
                 }
 
                 upsampleLeft = UseIntraEdgeUpsample(transformHeight, transformWidth, angle - 180, filterType);
@@ -1040,11 +1069,11 @@ internal class Av1PredictionDecoder
                 {
                     int pixelCount = transformHeight + (needBottom ? transformWidth : 0);
 
-                    UpsampleIntraEdge(leftColumn, pixelCount, bitDepth);
+                    UpsampleIntraEdge(leftColumn, pixelCount, bitDepth, edgeScratch);
                 }
             }
 
-            DirectionalPredictor(destination, destinationStride, transformSize, aboveRow, leftColumn, upsampleAbove, upsampleLeft, angle, bitDepth);
+            this.DirectionalPredictor(destination, destinationStride, transformSize, aboveRow, leftColumn, upsampleAbove, upsampleLeft, angle);
             return;
         }
 
@@ -1073,29 +1102,34 @@ internal class Av1PredictionDecoder
     private static void DcPredictor<T>(bool hasLeft, bool hasAbove, Av1TransformSize transformSize, Span<T> destination, nuint destinationStride, Span<T> above, Span<T> left, int bitDepth)
         where T : unmanaged
     {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+
         // DecodeCore is reachable only through byte and short overloads, so this type
         // dispatch permits shared reference preparation without boxing or allocating.
         if (typeof(T) == typeof(byte))
         {
-            Av1PredictorFactory.DcPredictor(
+            Av1DcIntraPredictor.Predict(
                 hasLeft,
                 hasAbove,
-                transformSize,
                 MemoryMarshal.Cast<T, byte>(destination),
-                destinationStride,
+                (int)destinationStride,
                 MemoryMarshal.Cast<T, byte>(above),
-                MemoryMarshal.Cast<T, byte>(left));
+                MemoryMarshal.Cast<T, byte>(left),
+                width,
+                height);
         }
         else
         {
-            Av1PredictorFactory.DcPredictor(
+            Av1DcIntraPredictor.Predict(
                 hasLeft,
                 hasAbove,
-                transformSize,
                 MemoryMarshal.Cast<T, short>(destination),
-                destinationStride,
+                (int)destinationStride,
                 MemoryMarshal.Cast<T, short>(above),
                 MemoryMarshal.Cast<T, short>(left),
+                width,
+                height,
                 bitDepth);
         }
     }
@@ -1113,25 +1147,29 @@ internal class Av1PredictionDecoder
     private static void GeneralPredictor<T>(Av1PredictionMode mode, Av1TransformSize transformSize, Span<T> destination, nuint destinationStride, Span<T> above, Span<T> left)
         where T : unmanaged
     {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+        Av1IntraPredictorBase predictor = Av1IntraPredictorBase.GetPredictor(mode);
+
         if (typeof(T) == typeof(byte))
         {
-            Av1PredictorFactory.GeneralPredictor(
+            predictor.Predict(
-                mode,
-                transformSize,
                 MemoryMarshal.Cast<T, byte>(destination),
-                destinationStride,
+                (int)destinationStride,
                 MemoryMarshal.Cast<T, byte>(above),
-                MemoryMarshal.Cast<T, byte>(left));
+                MemoryMarshal.Cast<T, byte>(left),
+                width,
+                height);
         }
         else
         {
-            Av1PredictorFactory.GeneralPredictor(
+            predictor.Predict(
-                mode,
-                transformSize,
                 MemoryMarshal.Cast<T, short>(destination),
-                destinationStride,
+                (int)destinationStride,
                 MemoryMarshal.Cast<T, short>(above),
-                MemoryMarshal.Cast<T, short>(left));
+                MemoryMarshal.Cast<T, short>(left),
+                width,
+                height);
         }
     }
 
@@ -1147,34 +1185,35 @@ internal class Av1PredictionDecoder
     /// <param name="upsampleAbove">A value indicating whether the top edge was upsampled.</param>
     /// <param name="upsampleLeft">A value indicating whether the left edge was upsampled.</param>
     /// <param name="angle">The adjusted prediction angle in degrees.</param>
-    /// <param name="bitDepth">The number of bits used to represent each sample.</param>
+    private void DirectionalPredictor<T>(Span<T> destination, nuint destinationStride, Av1TransformSize transformSize, Span<T> above, Span<T> left, bool upsampleAbove, bool upsampleLeft, int angle)
-    private static void DirectionalPredictor<T>(Span<T> destination, nuint destinationStride, Av1TransformSize transformSize, Span<T> above, Span<T> left, bool upsampleAbove, bool upsampleLeft, int angle, int bitDepth)
         where T : unmanaged
     {
         if (typeof(T) == typeof(byte))
         {
-            Av1PredictorFactory.DirectionalPredictor(
+            Span<byte> scratch = MemoryMarshal.AsBytes(this.predictorScratch.Span)[..Av1DirectionalIntraPredictor.ScratchLength];
+            Av1DirectionalIntraPredictor.Predict(
                 MemoryMarshal.Cast<T, byte>(destination),
-                destinationStride,
+                (int)destinationStride,
                 transformSize,
                 MemoryMarshal.Cast<T, byte>(above),
                 MemoryMarshal.Cast<T, byte>(left),
                 upsampleAbove,
                 upsampleLeft,
-                angle);
+                angle,
+                scratch);
         }
         else
         {
-            Av1PredictorFactory.DirectionalPredictor(
+            Av1DirectionalIntraPredictor.Predict(
                 MemoryMarshal.Cast<T, short>(destination),
-                destinationStride,
+                (int)destinationStride,
                 transformSize,
                 MemoryMarshal.Cast<T, short>(above),
                 MemoryMarshal.Cast<T, short>(left),
                 upsampleAbove,
                 upsampleLeft,
                 angle,
-                bitDepth);
+                this.predictorScratch.Span);
         }
     }
 
@@ -1189,29 +1228,36 @@ internal class Av1PredictionDecoder
     /// <param name="left">The prepared left reference samples.</param>
     /// <param name="mode">The filter intra mode whose coefficient set is applied.</param>
     /// <param name="bitDepth">The number of bits used to represent each sample.</param>
-    private static void FilterIntraPredictor<T>(Span<T> destination, nuint destinationStride, Av1TransformSize transformSize, Span<T> above, Span<T> left, Av1FilterIntraMode mode, int bitDepth)
+    private void FilterIntraPredictor<T>(Span<T> destination, nuint destinationStride, Av1TransformSize transformSize, Span<T> above, Span<T> left, Av1FilterIntraMode mode, int bitDepth)
         where T : unmanaged
     {
+        int width = transformSize.GetWidth();
+        int height = transformSize.GetHeight();
+        Av1FilterIntraPredictorBase predictor = Av1FilterIntraPredictorBase.GetPredictor(mode);
+
         if (typeof(T) == typeof(byte))
         {
-            Av1PredictorFactory.FilterIntraPredictor(
+            Span<byte> scratch = MemoryMarshal.AsBytes(this.predictorScratch.Span)[..Av1FilterIntraPredictorBase.ScratchLength];
+            predictor.Predict(
                 MemoryMarshal.Cast<T, byte>(destination),
-                destinationStride,
+                (int)destinationStride,
-                transformSize,
                 MemoryMarshal.Cast<T, byte>(above),
                 MemoryMarshal.Cast<T, byte>(left),
-                mode);
+                width,
+                height,
+                scratch);
         }
         else
         {
-            Av1PredictorFactory.FilterIntraPredictor(
+            predictor.Predict(
                 MemoryMarshal.Cast<T, short>(destination),
-                destinationStride,
+                (int)destinationStride,
-                transformSize,
                 MemoryMarshal.Cast<T, short>(above),
                 MemoryMarshal.Cast<T, short>(left),
-                mode,
+                width,
-                bitDepth);
+                height,
+                bitDepth,
+                this.predictorScratch.Span[..Av1FilterIntraPredictorBase.ScratchLength]);
         }
     }
 
@@ -1222,36 +1268,199 @@ internal class Av1PredictionDecoder
     /// <param name="buffer">The edge buffer, including writable prefix storage at indices -2 and -1.</param>
     /// <param name="count">The number of original edge samples to upsample.</param>
     /// <param name="bitDepth">The number of bits used to clamp interpolated samples.</param>
-    private static void UpsampleIntraEdge<T>(Span<T> buffer, int count, int bitDepth)
+    /// <param name="scratch">The reusable padded source workspace.</param>
+    private static void UpsampleIntraEdge<T>(Span<T> buffer, int count, int bitDepth, Span<T> scratch)
         where T : unmanaged, IBinaryInteger<T>
     {
-        // TODO: Consider creating SIMD version
         DebugGuard.MustBeLessThanOrEqualTo(count, MaxUpsampleSize, nameof(count));
 
-        Span<T> input = stackalloc T[MaxUpsampleSize + 3];
+        // DecodeBuildIntraPredictors is closed only over byte and short. Keeping that dispatch outside the
-        T beforeBuffer = Unsafe.Subtract(ref buffer[0], 1);
+        // kernels gives the JIT concrete vector element types and removes generic arithmetic from their loops.
+        if (typeof(T) == typeof(byte))
+        {
+            UpsampleIntraEdge(MemoryMarshal.Cast<T, byte>(buffer), count, MemoryMarshal.Cast<T, byte>(scratch));
+        }
+        else
+        {
+            UpsampleIntraEdge(MemoryMarshal.Cast<T, short>(buffer), count, bitDepth, MemoryMarshal.Cast<T, short>(scratch));
+        }
+    }
+
+    /// <summary>
+    /// Inserts half-sample positions into an 8-bit intra-prediction edge.
+    /// </summary>
+    /// <param name="buffer">The edge buffer, including writable prefix storage at indices -2 and -1.</param>
+    /// <param name="count">The number of original edge samples to upsample.</param>
+    /// <param name="scratch">The reusable padded source workspace.</param>
+    public static void UpsampleIntraEdge(Span<byte> buffer, int count, Span<byte> scratch)
+    {
+        ref byte bufferBase = ref MemoryMarshal.GetReference(buffer);
+        ref byte inputBase = ref MemoryMarshal.GetReference(scratch);
+        byte beforeBuffer = Unsafe.Subtract(ref bufferBase, 1);
+        byte finalSample = Unsafe.Add(ref bufferBase, count - 1);
+
+        // Vector loads intentionally extend past the logical edge. Initializing the complete load window with
+        // the final sample provides the AV1 endpoint extension and keeps every unaligned read inside scratch.
+        scratch[..32].Fill(finalSample);
+        inputBase = beforeBuffer;
+        Unsafe.Add(ref inputBase, 1) = beforeBuffer;
+        buffer[..count].CopyTo(scratch[2..]);
+        Unsafe.Subtract(ref bufferBase, 2) = beforeBuffer;
+
+        int i = 0;
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int eightSamplesFromEnd = count - 8;
+            for (; i <= eightSamplesFromEnd; i += 8)
+            {
+                Vector128<byte> interpolated = InterpolateEightBytes(ref inputBase, i);
+                Vector128<byte> originals = Vector128.LoadUnsafe(ref inputBase, (nuint)(i + 2));
+                Vector128<byte> interleaved = Vector128_.UnpackLow(interpolated, originals);
+                interleaved.StoreUnsafe(ref Unsafe.Add(ref bufferBase, (2 * i) - 1));
+            }
+
+            // AV1 upsampled edges are normally multiples of four. A half-vector store handles that common
+            // remainder without overwriting the prepared extension beyond the logical output edge.
+            if (i <= count - 4)
+            {
+                Vector128<byte> interpolated = InterpolateEightBytes(ref inputBase, i);
+                Vector128<byte> originals = Vector128.LoadUnsafe(ref inputBase, (nuint)(i + 2));
+                Vector128<byte> interleaved = Vector128_.UnpackLow(interpolated, originals);
+                Unsafe.As<byte, ulong>(ref Unsafe.Add(ref bufferBase, (2 * i) - 1)) = interleaved.AsUInt64().GetElement(0);
+                i += 4;
+            }
+        }
 
-        // Duplicate both endpoints so the four-tap interpolation kernel can run at
+        UpsampleIntraEdgeScalar(ref bufferBase, ref inputBase, i, count, 255);
-        // the edge without a separate boundary branch for its outer samples.
+    }
-        input[0] = beforeBuffer;
+
-        input[1] = beforeBuffer;
+    /// <summary>
-        for (int i = 0; i < count; i++)
+    /// Inserts half-sample positions into a high-bit-depth intra-prediction edge.
+    /// </summary>
+    /// <param name="buffer">The edge buffer, including writable prefix storage at indices -2 and -1.</param>
+    /// <param name="count">The number of original edge samples to upsample.</param>
+    /// <param name="bitDepth">The number of bits used to clamp interpolated samples.</param>
+    /// <param name="scratch">The reusable padded source workspace.</param>
+    public static void UpsampleIntraEdge(Span<short> buffer, int count, int bitDepth, Span<short> scratch)
+    {
+        ref short bufferBase = ref MemoryMarshal.GetReference(buffer);
+        ref short inputBase = ref MemoryMarshal.GetReference(scratch);
+        short beforeBuffer = Unsafe.Subtract(ref bufferBase, 1);
+        short finalSample = Unsafe.Add(ref bufferBase, count - 1);
+
+        // The same padded layout is used for 10- and 12-bit edges. Arithmetic widens to Int32 before applying
+        // the four-tap kernel because the 12-bit intermediate exceeds the unsigned 16-bit range.
+        scratch[..32].Fill(finalSample);
+        inputBase = beforeBuffer;
+        Unsafe.Add(ref inputBase, 1) = beforeBuffer;
+        buffer[..count].CopyTo(scratch[2..]);
+        Unsafe.Subtract(ref bufferBase, 2) = beforeBuffer;
+
+        int maximum = (1 << bitDepth) - 1;
+        int i = 0;
+        if (Vector128.IsHardwareAccelerated)
         {
-            input[i + 2] = buffer[i];
+            int eightSamplesFromEnd = count - 8;
+            for (; i <= eightSamplesFromEnd; i += 8)
+            {
+                Vector128<short> interpolated = InterpolateEightHighBitDepthSamples(ref inputBase, i, maximum);
+                Vector128<short> originals = Vector128.LoadUnsafe(ref inputBase, (nuint)(i + 2));
+                Vector128<short> interleavedLow = Vector128_.UnpackLow(interpolated, originals);
+                Vector128<short> interleavedHigh = Vector128_.UnpackHigh(interpolated, originals);
+                ref short destination = ref Unsafe.Add(ref bufferBase, (2 * i) - 1);
+
+                interleavedLow.StoreUnsafe(ref destination);
+                interleavedHigh.StoreUnsafe(ref destination, (nuint)Vector128<short>.Count);
+            }
+
+            if (i <= count - 4)
+            {
+                Vector128<short> interpolated = InterpolateEightHighBitDepthSamples(ref inputBase, i, maximum);
+                Vector128<short> originals = Vector128.LoadUnsafe(ref inputBase, (nuint)(i + 2));
+                Vector128<short> interleaved = Vector128_.UnpackLow(interpolated, originals);
+                interleaved.StoreUnsafe(ref Unsafe.Add(ref bufferBase, (2 * i) - 1));
+                i += 4;
+            }
         }
 
-        input[count + 2] = buffer[count - 1];
+        UpsampleIntraEdgeScalar(ref bufferBase, ref inputBase, i, count, maximum);
+    }
+
+    /// <summary>
+    /// Calculates eight 8-bit half-sample values in parallel.
+    /// </summary>
+    /// <param name="input">The first padded input sample.</param>
+    /// <param name="offset">The first output sample index.</param>
+    /// <returns>The interpolated samples in the lower eight lanes.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<byte> InterpolateEightBytes(ref byte input, int offset)
+    {
+        Vector128<byte> source0 = Vector128.LoadUnsafe(ref input, (nuint)offset);
+        Vector128<byte> source1 = Vector128.LoadUnsafe(ref input, (nuint)(offset + 1));
+        Vector128<byte> source2 = Vector128.LoadUnsafe(ref input, (nuint)(offset + 2));
+        Vector128<byte> source3 = Vector128.LoadUnsafe(ref input, (nuint)(offset + 3));
+        (Vector128<ushort> source0Low, _) = Vector128.Widen(source0);
+        (Vector128<ushort> source1Low, _) = Vector128.Widen(source1);
+        (Vector128<ushort> source2Low, _) = Vector128.Widen(source2);
+        (Vector128<ushort> source3Low, _) = Vector128.Widen(source3);
+        Vector128<short> interpolation = (((source1Low + source2Low) * Vector128.Create((ushort)9)) - (source0Low + source3Low)).AsInt16();
+
+        interpolation = Vector128.Clamp((interpolation + Vector128.Create((short)8)) >> 4, Vector128<short>.Zero, Vector128.Create((short)255));
+        return Vector128.Narrow(interpolation.AsUInt16(), Vector128<ushort>.Zero);
+    }
+
+    /// <summary>
+    /// Calculates eight high-bit-depth half-sample values in parallel.
+    /// </summary>
+    /// <param name="input">The first padded input sample.</param>
+    /// <param name="offset">The first output sample index.</param>
+    /// <param name="maximum">The maximum reconstructed sample value.</param>
+    /// <returns>The interpolated samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<short> InterpolateEightHighBitDepthSamples(ref short input, int offset, int maximum)
+    {
+        Vector128<short> source0 = Vector128.LoadUnsafe(ref input, (nuint)offset);
+        Vector128<short> source1 = Vector128.LoadUnsafe(ref input, (nuint)(offset + 1));
+        Vector128<short> source2 = Vector128.LoadUnsafe(ref input, (nuint)(offset + 2));
+        Vector128<short> source3 = Vector128.LoadUnsafe(ref input, (nuint)(offset + 3));
+        (Vector128<int> source0Low, Vector128<int> source0High) = Vector128.Widen(source0);
+        (Vector128<int> source1Low, Vector128<int> source1High) = Vector128.Widen(source1);
+        (Vector128<int> source2Low, Vector128<int> source2High) = Vector128.Widen(source2);
+        (Vector128<int> source3Low, Vector128<int> source3High) = Vector128.Widen(source3);
+        Vector128<int> coefficient = Vector128.Create(9);
+        Vector128<int> rounding = Vector128.Create(8);
+        Vector128<int> maximumVector = Vector128.Create(maximum);
+        Vector128<int> low = ((((source1Low + source2Low) * coefficient) - (source0Low + source3Low)) + rounding) >> 4;
+        Vector128<int> high = ((((source1High + source2High) * coefficient) - (source0High + source3High)) + rounding) >> 4;
+
+        low = Vector128.Clamp(low, Vector128<int>.Zero, maximumVector);
+        high = Vector128.Clamp(high, Vector128<int>.Zero, maximumVector);
+        return Vector128.Narrow(low, high);
+    }
 
-        Unsafe.Subtract(ref buffer[0], 2) = input[0];
+    /// <summary>
-        ref T output = ref buffer[0];
+    /// Inserts the scalar remainder of an intra-edge upsample operation.
-        for (int i = 0; i < count; i++)
+    /// </summary>
+    /// <typeparam name="T">The byte or 16-bit sample type.</typeparam>
+    /// <param name="buffer">The first original edge sample.</param>
+    /// <param name="input">The first padded input sample.</param>
+    /// <param name="start">The first sample not processed by SIMD.</param>
+    /// <param name="count">The number of original edge samples.</param>
+    /// <param name="maximum">The maximum reconstructed sample value.</param>
+    private static void UpsampleIntraEdgeScalar<T>(ref T buffer, ref T input, int start, int count, int maximum)
+        where T : unmanaged, IBinaryInteger<T>
+    {
+        for (int i = start; i < count; i++)
         {
-            int s = -int.CreateChecked(input[i]) + (9 * int.CreateChecked(input[i + 1])) + (9 * int.CreateChecked(input[i + 2])) - int.CreateChecked(input[i + 3]);
+            int interpolation = -int.CreateChecked(Unsafe.Add(ref input, i))
-            s = Av1Math.Clamp((s + 8) >> 4, 0, (1 << bitDepth) - 1);
+                + (9 * int.CreateChecked(Unsafe.Add(ref input, i + 1)))
+                + (9 * int.CreateChecked(Unsafe.Add(ref input, i + 2)))
+                - int.CreateChecked(Unsafe.Add(ref input, i + 3));
+
+            interpolation = Av1Math.Clamp((interpolation + 8) >> 4, 0, maximum);
 
-            // The AOM edge buffer reserves prefix storage for the samples at indices -2 and -1.
+            Unsafe.Add(ref buffer, (2 * i) - 1) = T.CreateChecked(interpolation);
-            Unsafe.Add(ref output, (2 * i) - 1) = T.CreateChecked(s);
+            Unsafe.Add(ref buffer, 2 * i) = Unsafe.Add(ref input, i + 2);
-            Unsafe.Add(ref output, 2 * i) = input[i + 2];
         }
     }
 
@@ -1283,38 +1492,261 @@ internal class Av1PredictionDecoder
     /// <param name="buffer">A reference to the first edge sample to filter.</param>
     /// <param name="count">The number of edge samples.</param>
     /// <param name="strength">The AV1 filter-strength index from zero through three.</param>
+    /// <param name="scratch">The reusable padded source workspace.</param>
     /// <remarks>Corresponds to <c>svt_av1_filter_intra_edge_c</c> in SVT-AV1.</remarks>
-    private static void FilterIntraEdge<T>(ref T buffer, int count, int strength)
+    private static void FilterIntraEdge<T>(ref T buffer, int count, int strength, Span<T> scratch)
         where T : unmanaged, IBinaryInteger<T>
     {
-        // TODO: Consider creating SIMD version
         if (strength == 0)
         {
             return;
         }
 
-        int[][] kernel = [
+        // As with edge upsampling, closing the kernel over a concrete sample type keeps vector arithmetic
-            [0, 4, 8, 4, 0], [0, 5, 6, 5, 0], [2, 4, 4, 4, 2]
+        // outside the generic decoder while the valid strength-zero no-op remains at the owning boundary.
-        ];
+        if (typeof(T) == typeof(byte))
-        int filt = strength - 1;
+        {
-        Span<T> edge = stackalloc T[129];
+            FilterIntraEdge(ref Unsafe.As<T, byte>(ref buffer), count, strength, MemoryMarshal.Cast<T, byte>(scratch));
+        }
+        else
+        {
+            FilterIntraEdge(ref Unsafe.As<T, short>(ref buffer), count, strength, MemoryMarshal.Cast<T, short>(scratch));
+        }
+    }
 
-        // Filtering must read the original edge throughout the convolution, so retain
+    /// <summary>
-        // a scratch copy rather than feeding earlier filtered samples into later outputs.
+    /// Applies an AV1 intra-edge smoothing kernel to 8-bit samples.
-        MemoryMarshal.CreateSpan(ref buffer, count).CopyTo(edge);
+    /// </summary>
-        for (int i = 1; i < count; i++)
+    /// <param name="buffer">A reference to the first edge sample to filter.</param>
+    /// <param name="count">The number of edge samples.</param>
+    /// <param name="strength">The AV1 filter-strength index from one through three.</param>
+    /// <param name="scratch">The reusable padded source workspace.</param>
+    public static void FilterIntraEdge(ref byte buffer, int count, int strength, Span<byte> scratch)
+    {
+        byte finalSample = Unsafe.Add(ref buffer, count - 1);
+
+        // The original edge is retained because each convolution window must observe unfiltered neighbors.
+        // Padding both endpoints also makes every complete vector use the same contiguous load pattern.
+        scratch[..EdgeScratchLength].Fill(finalSample);
+        scratch[0] = buffer;
+        MemoryMarshal.CreateReadOnlySpan(ref buffer, count).CopyTo(scratch[1..]);
+
+        ref byte edge = ref MemoryMarshal.GetReference(scratch);
+        int outputCount = count - 1;
+        int processed = 0;
+        if (Vector128.IsHardwareAccelerated)
         {
-            int s = 0;
+            int eightSamplesFromEnd = outputCount - 8;
-            for (int j = 0; j < 5; j++)
+            switch (strength)
             {
-                int k = i - 2 + j;
+                case 1:
-                k = (k < 0) ? 0 : k;
+                    for (; processed <= eightSamplesFromEnd; processed += 8)
-                k = (k > count - 1) ? count - 1 : k;
+                    {
-                s += int.CreateChecked(edge[k]) * kernel[filt][j];
+                        Vector128<ushort> source0 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 1)));
+                        Vector128<ushort> source1 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 2)));
+                        Vector128<ushort> source2 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 3)));
+                        Vector128<byte> result = Vector128.Narrow(FilterEdgeStrength1(source0, source1, source2), Vector128<ushort>.Zero);
+                        Unsafe.As<byte, ulong>(ref Unsafe.Add(ref buffer, processed + 1)) = result.AsUInt64().GetElement(0);
+                    }
+
+                    break;
+                case 2:
+                    for (; processed <= eightSamplesFromEnd; processed += 8)
+                    {
+                        Vector128<ushort> source0 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 1)));
+                        Vector128<ushort> source1 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 2)));
+                        Vector128<ushort> source2 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 3)));
+                        Vector128<byte> result = Vector128.Narrow(FilterEdgeStrength2(source0, source1, source2), Vector128<ushort>.Zero);
+                        Unsafe.As<byte, ulong>(ref Unsafe.Add(ref buffer, processed + 1)) = result.AsUInt64().GetElement(0);
+                    }
+
+                    break;
+                default:
+                    for (; processed <= eightSamplesFromEnd; processed += 8)
+                    {
+                        Vector128<ushort> source0 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)processed));
+                        Vector128<ushort> source1 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 1)));
+                        Vector128<ushort> source2 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 2)));
+                        Vector128<ushort> source3 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 3)));
+                        Vector128<ushort> source4 = WidenLower(Vector128.LoadUnsafe(ref edge, (nuint)(processed + 4)));
+                        Vector128<byte> result = Vector128.Narrow(FilterEdgeStrength3(source0, source1, source2, source3, source4), Vector128<ushort>.Zero);
+                        Unsafe.As<byte, ulong>(ref Unsafe.Add(ref buffer, processed + 1)) = result.AsUInt64().GetElement(0);
+                    }
+
+                    break;
             }
+        }
+
+        FilterIntraEdgeScalar(ref buffer, ref edge, processed, outputCount, strength);
+    }
 
-            s = (s + 8) >> 4;
+    /// <summary>
-            Unsafe.Add(ref buffer, i) = T.CreateChecked(s);
+    /// Applies an AV1 intra-edge smoothing kernel to high-bit-depth samples.
+    /// </summary>
+    /// <param name="buffer">A reference to the first edge sample to filter.</param>
+    /// <param name="count">The number of edge samples.</param>
+    /// <param name="strength">The AV1 filter-strength index from one through three.</param>
+    /// <param name="scratch">The reusable padded source workspace.</param>
+    public static void FilterIntraEdge(ref short buffer, int count, int strength, Span<short> scratch)
+    {
+        short finalSample = Unsafe.Add(ref buffer, count - 1);
+
+        scratch[..EdgeScratchLength].Fill(finalSample);
+        scratch[0] = buffer;
+        MemoryMarshal.CreateReadOnlySpan(ref buffer, count).CopyTo(scratch[1..]);
+
+        ref short edge = ref MemoryMarshal.GetReference(scratch);
+        int outputCount = count - 1;
+        int processed = 0;
+
+        // The largest 12-bit weighted sum is 65520; the greatest rounding bias raises that only to 65528.
+        // Unsigned 16-bit lanes therefore preserve every normative strength without widening to 32-bit vectors.
+        if (Vector128.IsHardwareAccelerated)
+        {
+            int eightSamplesFromEnd = outputCount - Vector128<short>.Count;
+            switch (strength)
+            {
+                case 1:
+                    for (; processed <= eightSamplesFromEnd; processed += Vector128<short>.Count)
+                    {
+                        Vector128<ushort> source0 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 1)).AsUInt16();
+                        Vector128<ushort> source1 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 2)).AsUInt16();
+                        Vector128<ushort> source2 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 3)).AsUInt16();
+                        FilterEdgeStrength1(source0, source1, source2).AsInt16().StoreUnsafe(ref buffer, (nuint)(processed + 1));
+                    }
+
+                    break;
+                case 2:
+                    for (; processed <= eightSamplesFromEnd; processed += Vector128<short>.Count)
+                    {
+                        Vector128<ushort> source0 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 1)).AsUInt16();
+                        Vector128<ushort> source1 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 2)).AsUInt16();
+                        Vector128<ushort> source2 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 3)).AsUInt16();
+                        FilterEdgeStrength2(source0, source1, source2).AsInt16().StoreUnsafe(ref buffer, (nuint)(processed + 1));
+                    }
+
+                    break;
+                default:
+                    for (; processed <= eightSamplesFromEnd; processed += Vector128<short>.Count)
+                    {
+                        Vector128<ushort> source0 = Vector128.LoadUnsafe(ref edge, (nuint)processed).AsUInt16();
+                        Vector128<ushort> source1 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 1)).AsUInt16();
+                        Vector128<ushort> source2 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 2)).AsUInt16();
+                        Vector128<ushort> source3 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 3)).AsUInt16();
+                        Vector128<ushort> source4 = Vector128.LoadUnsafe(ref edge, (nuint)(processed + 4)).AsUInt16();
+                        FilterEdgeStrength3(source0, source1, source2, source3, source4).AsInt16().StoreUnsafe(ref buffer, (nuint)(processed + 1));
+                    }
+
+                    break;
+            }
+        }
+
+        FilterIntraEdgeScalar(ref buffer, ref edge, processed, outputCount, strength);
+    }
+
+    /// <summary>
+    /// Widens the lower eight lanes of a byte vector for edge-filter arithmetic.
+    /// </summary>
+    /// <param name="source">The packed source samples.</param>
+    /// <returns>The widened samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<ushort> WidenLower(Vector128<byte> source)
+    {
+        (Vector128<ushort> lower, _) = Vector128.Widen(source);
+        return lower;
+    }
+
+    /// <summary>
+    /// Applies the strength-one three-tap edge filter to eight samples.
+    /// </summary>
+    /// <param name="source0">The preceding samples.</param>
+    /// <param name="source1">The centered samples.</param>
+    /// <param name="source2">The following samples.</param>
+    /// <returns>The filtered samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<ushort> FilterEdgeStrength1(Vector128<ushort> source0, Vector128<ushort> source1, Vector128<ushort> source2)
+        => (source0 + (source1 << 1) + source2 + Vector128.Create((ushort)2)) >> 2;
+
+    /// <summary>
+    /// Applies the strength-two three-tap edge filter to eight samples.
+    /// </summary>
+    /// <param name="source0">The preceding samples.</param>
+    /// <param name="source1">The centered samples.</param>
+    /// <param name="source2">The following samples.</param>
+    /// <returns>The filtered samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<ushort> FilterEdgeStrength2(Vector128<ushort> source0, Vector128<ushort> source1, Vector128<ushort> source2)
+        => (((source0 + source2) * Vector128.Create((ushort)5)) + (source1 * Vector128.Create((ushort)6)) + Vector128.Create((ushort)8)) >> 4;
+
+    /// <summary>
+    /// Applies the strength-three five-tap edge filter to eight samples.
+    /// </summary>
+    /// <param name="source0">The samples two positions before each output.</param>
+    /// <param name="source1">The preceding samples.</param>
+    /// <param name="source2">The centered samples.</param>
+    /// <param name="source3">The following samples.</param>
+    /// <param name="source4">The samples two positions after each output.</param>
+    /// <returns>The filtered samples.</returns>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    private static Vector128<ushort> FilterEdgeStrength3(
+        Vector128<ushort> source0,
+        Vector128<ushort> source1,
+        Vector128<ushort> source2,
+        Vector128<ushort> source3,
+        Vector128<ushort> source4)
+        => (source0 + ((source1 + source2 + source3) << 1) + source4 + Vector128.Create((ushort)4)) >> 3;
+
+    /// <summary>
+    /// Applies an AV1 edge filter to samples not consumed by the vector loop.
+    /// </summary>
+    /// <typeparam name="T">The byte or 16-bit sample type.</typeparam>
+    /// <param name="buffer">The first destination sample.</param>
+    /// <param name="edge">The first padded source sample.</param>
+    /// <param name="start">The first output index not processed by SIMD.</param>
+    /// <param name="count">The number of filtered outputs following the preserved first sample.</param>
+    /// <param name="strength">The AV1 filter-strength index.</param>
+    private static void FilterIntraEdgeScalar<T>(ref T buffer, ref T edge, int start, int count, int strength)
+        where T : unmanaged, IBinaryInteger<T>
+    {
+        switch (strength)
+        {
+            case 1:
+                for (int i = start; i < count; i++)
+                {
+                    int sourceOffset = i + 1;
+                    int value = int.CreateChecked(Unsafe.Add(ref edge, sourceOffset))
+                        + (2 * int.CreateChecked(Unsafe.Add(ref edge, sourceOffset + 1)))
+                        + int.CreateChecked(Unsafe.Add(ref edge, sourceOffset + 2));
+
+                    Unsafe.Add(ref buffer, i + 1) = T.CreateChecked((value + 2) >> 2);
+                }
+
+                break;
+            case 2:
+                for (int i = start; i < count; i++)
+                {
+                    int sourceOffset = i + 1;
+                    int value = (5 * int.CreateChecked(Unsafe.Add(ref edge, sourceOffset)))
+                        + (6 * int.CreateChecked(Unsafe.Add(ref edge, sourceOffset + 1)))
+                        + (5 * int.CreateChecked(Unsafe.Add(ref edge, sourceOffset + 2)));
+
+                    Unsafe.Add(ref buffer, i + 1) = T.CreateChecked((value + 8) >> 4);
+                }
+
+                break;
+            default:
+                for (int i = start; i < count; i++)
+                {
+                    int value = int.CreateChecked(Unsafe.Add(ref edge, i))
+                        + (2 * (int.CreateChecked(Unsafe.Add(ref edge, i + 1))
+                            + int.CreateChecked(Unsafe.Add(ref edge, i + 2))
+                            + int.CreateChecked(Unsafe.Add(ref edge, i + 3))))
+                        + int.CreateChecked(Unsafe.Add(ref edge, i + 4));
+
+                    Unsafe.Add(ref buffer, i + 1) = T.CreateChecked((value + 4) >> 3);
+                }
+
+                break;
         }
     }
 

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1PredictorFactory.cs

@@ -1,275 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using SixLabors.ImageSharp.Formats.Heif.Av1.Tiling;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Selects the scalar 8-bit or high-bit-depth AV1 intra predictor for a decoded prediction mode.
-/// </summary>
-internal class Av1PredictorFactory
-{
-    /// <summary>
-    /// The Q8 directional derivatives indexed by acute angle in degrees; zero entries represent angles AV1 does not signal.
-    /// </summary>
-    private static readonly int[] DirectionalIntraDerivative = [
-
-        // More evenly spread out angles and limited to 10-bit
-        // Values that are 0 will never be used
-        //                    Approx angle
-        0,    0, 0,        // 0
-        1023, 0, 0,        // 3, ...
-        547,  0, 0,        // 6, ...
-        372,  0, 0, 0, 0,  // 9, ...
-        273,  0, 0,        // 14, ...
-        215,  0, 0,        // 17, ...
-        178,  0, 0,        // 20, ...
-        151,  0, 0,        // 23, ... (113 & 203 are base angles)
-        132,  0, 0,        // 26, ...
-        116,  0, 0,        // 29, ...
-        102,  0, 0, 0,     // 32, ...
-        90,   0, 0,        // 36, ...
-        80,   0, 0,        // 39, ...
-        71,   0, 0,        // 42, ...
-        64,   0, 0,        // 45, ... (45 & 135 are base angles)
-        57,   0, 0,        // 48, ...
-        51,   0, 0,        // 51, ...
-        45,   0, 0, 0,     // 54, ...
-        40,   0, 0,        // 58, ...
-        35,   0, 0,        // 61, ...
-        31,   0, 0,        // 64, ...
-        27,   0, 0,        // 67, ... (67 & 157 are base angles)
-        23,   0, 0,        // 70, ...
-        19,   0, 0,        // 73, ...
-        15,   0, 0, 0, 0,  // 76, ...
-        11,   0, 0,        // 81, ...
-        7,    0, 0,        // 84, ...
-        3,    0, 0,        // 87, ...
-    ];
-
-    /// <summary>
-    /// Predicts an 8-bit block from the average of whichever top and left neighbor edges are available.
-    /// </summary>
-    /// <param name="hasLeft">Whether the left neighboring column is available.</param>
-    /// <param name="hasAbove">Whether the top neighboring row is available.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="aboveRow">The top neighboring samples.</param>
-    /// <param name="leftColumn">The left neighboring samples.</param>
-    public static void DcPredictor(bool hasLeft, bool hasAbove, Av1TransformSize transformSize, Span<byte> destination, nuint destinationStride, Span<byte> aboveRow, Span<byte> leftColumn)
-    {
-        if (hasLeft)
-        {
-            if (hasAbove)
-            {
-                Av1DcPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-            }
-            else
-            {
-                Av1DcLeftPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-            }
-        }
-        else
-        {
-            if (hasAbove)
-            {
-                Av1DcTopPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-            }
-            else
-            {
-                Av1DcFillPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-            }
-        }
-    }
-
-    /// <summary>
-    /// Predicts a high-bit-depth block from the average of whichever top and left neighbor edges are available.
-    /// </summary>
-    /// <param name="hasLeft">Whether the left neighboring column is available.</param>
-    /// <param name="hasAbove">Whether the top neighboring row is available.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="aboveRow">The top neighboring samples.</param>
-    /// <param name="leftColumn">The left neighboring samples.</param>
-    /// <param name="bitDepth">The coded sample bit depth used to select the midpoint when no edge is available.</param>
-    public static void DcPredictor(bool hasLeft, bool hasAbove, Av1TransformSize transformSize, Span<short> destination, nuint destinationStride, Span<short> aboveRow, Span<short> leftColumn, int bitDepth)
-        => Av1HighBitDepthPredictor.DcPredictor(hasLeft, hasAbove, transformSize, destination, destinationStride, aboveRow, leftColumn, bitDepth);
-
-    /// <summary>
-    /// Predicts an 8-bit block by projecting reference-edge samples along a directional angle.
-    /// </summary>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="aboveRow">The top and top-right reference samples.</param>
-    /// <param name="leftColumn">The left and bottom-left reference samples.</param>
-    /// <param name="upsampleAbove">Whether the top reference edge is stored at half-sample intervals.</param>
-    /// <param name="upsampleLeft">Whether the left reference edge is stored at half-sample intervals.</param>
-    /// <param name="angle">The prediction angle in degrees from 1 through 269.</param>
-    /// <remarks>SVT-AV1: <c>svt_aom_highbd_dr_predictor</c>.</remarks>
-    public static void DirectionalPredictor(Span<byte> destination, nuint stride, Av1TransformSize transformSize, Span<byte> aboveRow, Span<byte> leftColumn, bool upsampleAbove, bool upsampleLeft, int angle)
-    {
-        int dx = GetDeltaX(angle);
-        int dy = GetDeltaY(angle);
-        int bw = transformSize.GetWidth();
-        int bh = transformSize.GetHeight();
-        Guard.MustBeBetweenOrEqualTo(angle, 1, 269, nameof(angle));
-
-        // The three open quadrants select which reference edge or edge pair the projected ray intersects.
-        // Exact 90- and 180-degree modes reduce to copying the top row or left column without interpolation.
-        if (angle is > 0 and < 90)
-        {
-            Av1DirectionalZone1Predictor.PredictScalar(transformSize, destination, stride, aboveRow, upsampleAbove, dx);
-        }
-        else if (angle is > 90 and < 180)
-        {
-            Av1DirectionalZone2Predictor.PredictScalar(transformSize, destination, stride, aboveRow, leftColumn, upsampleAbove, upsampleLeft, dx, dy);
-        }
-        else if (angle is > 180 and < 270)
-        {
-            Av1DirectionalZone3Predictor.PredictScalar(transformSize, destination, stride, leftColumn, upsampleLeft, dx, dy);
-        }
-        else if (angle == 90)
-        {
-            Av1VerticalPredictor.PredictScalar(transformSize, destination, stride, aboveRow, leftColumn);
-        }
-        else if (angle == 180)
-        {
-            Av1HorizontalPredictor.PredictScalar(transformSize, destination, stride, aboveRow, leftColumn);
-        }
-    }
-
-    /// <summary>
-    /// Predicts a high-bit-depth block by projecting reference-edge samples along a directional angle.
-    /// </summary>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="aboveRow">The top and top-right reference samples.</param>
-    /// <param name="leftColumn">The left and bottom-left reference samples.</param>
-    /// <param name="upsampleAbove">Whether the top reference edge is stored at half-sample intervals.</param>
-    /// <param name="upsampleLeft">Whether the left reference edge is stored at half-sample intervals.</param>
-    /// <param name="angle">The prediction angle in degrees from 1 through 269.</param>
-    /// <param name="bitDepth">The coded sample bit depth used to clamp interpolated values.</param>
-    public static void DirectionalPredictor(Span<short> destination, nuint stride, Av1TransformSize transformSize, Span<short> aboveRow, Span<short> leftColumn, bool upsampleAbove, bool upsampleLeft, int angle, int bitDepth)
-        => Av1HighBitDepthPredictor.DirectionalPredictor(destination, stride, transformSize, aboveRow, leftColumn, upsampleAbove, upsampleLeft, angle, bitDepth);
-
-    /// <summary>
-    /// Predicts an 8-bit block using the selected AV1 filter-intra kernel.
-    /// </summary>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="aboveRow">The top neighboring samples.</param>
-    /// <param name="leftColumn">The left neighboring samples.</param>
-    /// <param name="filterIntraMode">The filter-intra coefficient set.</param>
-    public static void FilterIntraPredictor(Span<byte> destination, nuint destinationStride, Av1TransformSize transformSize, Span<byte> aboveRow, Span<byte> leftColumn, Av1FilterIntraMode filterIntraMode)
-        => Av1FilterIntraPredictor.Predict(destination, destinationStride, transformSize, aboveRow, leftColumn, filterIntraMode);
-
-    /// <summary>
-    /// Predicts a high-bit-depth block using the selected AV1 filter-intra kernel.
-    /// </summary>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="aboveRow">The top neighboring samples.</param>
-    /// <param name="leftColumn">The left neighboring samples.</param>
-    /// <param name="filterIntraMode">The filter-intra coefficient set.</param>
-    /// <param name="bitDepth">The coded sample bit depth used to clamp filtered values.</param>
-    public static void FilterIntraPredictor(Span<short> destination, nuint destinationStride, Av1TransformSize transformSize, Span<short> aboveRow, Span<short> leftColumn, Av1FilterIntraMode filterIntraMode, int bitDepth)
-        => Av1HighBitDepthPredictor.FilterIntraPredictor(destination, destinationStride, transformSize, aboveRow, leftColumn, filterIntraMode, bitDepth);
-
-    /// <summary>
-    /// Selects an 8-bit horizontal, vertical, Paeth, or smooth predictor for a non-directional mode.
-    /// </summary>
-    /// <param name="mode">The non-directional prediction mode.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="aboveRow">The top neighboring samples.</param>
-    /// <param name="leftColumn">The left neighboring samples.</param>
-    public static void GeneralPredictor(Av1PredictionMode mode, Av1TransformSize transformSize, Span<byte> destination, nuint destinationStride, Span<byte> aboveRow, Span<byte> leftColumn)
-    {
-        switch (mode)
-        {
-            case Av1PredictionMode.Horizontal:
-                Av1HorizontalPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-                break;
-            case Av1PredictionMode.Vertical:
-                Av1VerticalPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-                break;
-            case Av1PredictionMode.Paeth:
-                Av1PaethPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-                break;
-            case Av1PredictionMode.Smooth:
-                Av1SmoothPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-                break;
-            case Av1PredictionMode.SmoothHorizontal:
-                Av1SmoothHorizontalPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-                break;
-            case Av1PredictionMode.SmoothVertical:
-                Av1SmoothVerticalPredictor.PredictScalar(transformSize, destination, destinationStride, aboveRow, leftColumn);
-                break;
-        }
-    }
-
-    /// <summary>
-    /// Selects a high-bit-depth horizontal, vertical, Paeth, or smooth predictor for a non-directional mode.
-    /// </summary>
-    /// <param name="mode">The non-directional prediction mode.</param>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="destinationStride">The distance, in samples, between destination rows.</param>
-    /// <param name="aboveRow">The top neighboring samples.</param>
-    /// <param name="leftColumn">The left neighboring samples.</param>
-    public static void GeneralPredictor(Av1PredictionMode mode, Av1TransformSize transformSize, Span<short> destination, nuint destinationStride, Span<short> aboveRow, Span<short> leftColumn)
-        => Av1HighBitDepthPredictor.GeneralPredictor(mode, transformSize, destination, destinationStride, aboveRow, leftColumn);
-
-    /// <summary>
-    /// Gets the Q8 vertical displacement per unit horizontal displacement for a directional angle.
-    /// </summary>
-    /// <param name="angle">The prediction angle in degrees.</param>
-    /// <returns>The Q8 vertical derivative, or one when the selected directional zone does not consume it.</returns>
-    public static int GetDeltaY(int angle)
-    {
-        if (angle is > 90 and < 180)
-        {
-            return DirectionalIntraDerivative[angle - 90];
-        }
-        else if (angle is > 180 and < 270)
-        {
-            return DirectionalIntraDerivative[270 - angle];
-        }
-        else
-        {
-            // Zones one and the exact horizontal/vertical modes never consume dy; one avoids a zero placeholder.
-            return 1;
-        }
-    }
-
-    /// <summary>
-    /// Gets the Q8 horizontal displacement per unit vertical displacement for a directional angle.
-    /// </summary>
-    /// <param name="angle">The prediction angle in degrees.</param>
-    /// <returns>The Q8 horizontal derivative, or one when the selected directional zone does not consume it.</returns>
-    public static int GetDeltaX(int angle)
-    {
-        if (angle is > 0 and < 90)
-        {
-            return DirectionalIntraDerivative[angle];
-        }
-        else if (angle is > 90 and < 180)
-        {
-            return DirectionalIntraDerivative[180 - angle];
-        }
-        else
-        {
-            // Zone three and the exact horizontal/vertical modes never consume dx; one avoids a zero placeholder.
-            return 1;
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1SmoothHorizontalPredictor.cs

@@ -1,89 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block by smoothly blending each left neighbor toward the top-right reference sample.
-/// </summary>
-internal readonly struct Av1SmoothHorizontalPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of interpolation weights and samples written to each destination row.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The number of left samples consumed and destination rows written.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1SmoothHorizontalPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1SmoothHorizontalPredictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1SmoothHorizontalPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1SmoothHorizontalPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block using horizontal smooth interpolation.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top neighboring samples whose final value supplies the right endpoint.</param>
-    /// <param name="left">The left neighboring samples.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1SmoothHorizontalPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    /// <remarks>SVT-AV1: <c>highbd_smooth_h_predictor</c>.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte leftRef = ref left[0];
-        ref byte aboveRef = ref above[0];
-        ref byte destinationRef = ref destination[0];
-        int rightPrediction = Unsafe.Add(ref aboveRef, this.blockWidth - 1); // estimated by top-right pixel
-        ref int weights = ref Av1SmoothPredictor.Weights[(int)this.blockWidth];
-
-        int log2Scale = Av1SmoothPredictor.WeightLog2Scale;
-        int scale = 1 << Av1SmoothPredictor.WeightLog2Scale;
-
-        // sm_weights_sanity_checks(sm_weights_w, sm_weights_h, scale, log2_scale + 2);
-        for (nuint r = 0; r < this.blockHeight; ++r)
-        {
-            for (nuint c = 0; c < this.blockWidth; ++c)
-            {
-                int columnWeight = Unsafe.Add(ref weights, c);
-                Guard.MustBeGreaterThanOrEqualTo(scale, columnWeight, nameof(scale));
-
-                // The Q8 weight decreases toward the right edge, shifting influence from left to top-right.
-                int thisPredition = Unsafe.Add(ref leftRef, r) * columnWeight;
-                thisPredition += rightPrediction * (scale - columnWeight);
-                Unsafe.Add(ref destinationRef, c) = (byte)Av1Math.DivideRound(thisPredition, log2Scale);
-            }
-
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1SmoothPredictor.cs

@@ -1,135 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block by blending top-to-bottom and left-to-right smooth interpolation surfaces.
-/// </summary>
-internal readonly struct Av1SmoothPredictor : IAv1Predictor
-{
-    // Weights are quadratic from '1' to '1 / BlockSize', scaled by
-    // 2^sm_weight_log2_scale.
-
-    /// <summary>
-    /// The number of fractional bits in the normative smooth-prediction weights.
-    /// </summary>
-    internal static readonly int WeightLog2Scale = 8;
-
-    /// <summary>
-    /// The concatenated smooth-weight sequences, addressed by using the block dimension as the sequence offset.
-    /// </summary>
-    internal static readonly int[] Weights = [
-
-        // Unused, because we always offset by bs, which is at least 2.
-        0, 0,
-
-        // bs = 2
-        255, 128,
-
-        // bs = 4
-        255, 149, 85, 64,
-
-        // bs = 8
-        255, 197, 146, 105, 73, 50, 37, 32,
-
-        // bs = 16
-        255, 225, 196, 170, 145, 123, 102, 84, 68, 54, 43, 33, 26, 20, 17, 16,
-
-        // bs = 32
-        255, 240, 225, 210, 196, 182, 169, 157, 145, 133, 122, 111, 101, 92, 83, 74,
-        66, 59, 52, 45, 39, 34, 29, 25, 21, 17, 14, 12, 10, 9, 8, 8,
-
-        // bs = 64
-        255, 248, 240, 233, 225, 218, 210, 203, 196, 189, 182, 176, 169, 163, 156,
-        150, 144, 138, 133, 127, 121, 116, 111, 106, 101, 96, 91, 86, 82, 77, 73, 69,
-        65, 61, 57, 54, 50, 47, 44, 41, 38, 35, 32, 29, 27, 25, 22, 20, 18, 16, 15,
-        13, 12, 10, 9, 8, 7, 6, 6, 5, 5, 4, 4, 4,
-    ];
-
-    /// <summary>
-    /// The number of top samples consumed and samples written to each destination row.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The number of left samples consumed and destination rows written.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1SmoothPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1SmoothPredictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1SmoothPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1SmoothPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block by combining horizontal and vertical smooth interpolation.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top neighboring samples.</param>
-    /// <param name="left">The left neighboring samples.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1SmoothPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    /// <remarks>SVT-AV1: <c>highbd_smooth_predictor</c>.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte leftRef = ref left[0];
-        ref byte aboveRef = ref above[0];
-        ref byte destinationRef = ref destination[0];
-        int belowPrediction = Unsafe.Add(ref leftRef, this.blockHeight - 1); // estimated by bottom-left pixel
-        int rightPrediction = Unsafe.Add(ref aboveRef, this.blockWidth - 1); // estimated by top-right pixel
-        ref int heightWeights = ref Weights[(int)this.blockHeight];
-        ref int widthWeights = ref Weights[(int)this.blockWidth];
-
-        // The two independent interpolation surfaces each use Q8 weights, so their combined sum has one extra scale bit.
-        int log2Scale = 1 + WeightLog2Scale;
-        int scale = 1 << WeightLog2Scale;
-
-        // sm_weights_sanity_checks(sm_weights_w, sm_weights_h, scale, log2_scale + 2);
-        for (nuint r = 0; r < this.blockHeight; ++r)
-        {
-            int rowWeight = Unsafe.Add(ref heightWeights, r);
-            Guard.MustBeGreaterThanOrEqualTo(scale, rowWeight, nameof(scale));
-            for (nuint c = 0; c < this.blockWidth; ++c)
-            {
-                int columnWeight = Unsafe.Add(ref widthWeights, c);
-                Guard.MustBeGreaterThanOrEqualTo(scale, columnWeight, nameof(scale));
-
-                // Blend top toward bottom-left and left toward top-right, then normalize their combined Q8 contributions.
-                int thisPredition = Unsafe.Add(ref aboveRef, c) * rowWeight;
-                thisPredition += belowPrediction * (scale - rowWeight);
-                thisPredition += Unsafe.Add(ref leftRef, r) * columnWeight;
-                thisPredition += rightPrediction * (scale - columnWeight);
-                Unsafe.Add(ref destinationRef, c) = (byte)Av1Math.DivideRound(thisPredition, log2Scale);
-            }
-
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1SmoothVerticalPredictor.cs

@@ -1,87 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block by smoothly blending each top neighbor toward the bottom-left reference sample.
-/// </summary>
-internal readonly struct Av1SmoothVerticalPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of top samples consumed and samples written to each destination row.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The number of interpolation weights, left samples consumed, and destination rows written.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1SmoothVerticalPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1SmoothVerticalPredictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1SmoothVerticalPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1SmoothVerticalPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block using vertical smooth interpolation.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top neighboring samples.</param>
-    /// <param name="left">The left neighboring samples whose final value supplies the bottom endpoint.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1SmoothVerticalPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    /// <remarks>SVT-AV1: <c>highbd_smooth_v_predictor</c>.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte leftRef = ref left[0];
-        ref byte aboveRef = ref above[0];
-        ref byte destinationRef = ref destination[0];
-        int belowPrediction = Unsafe.Add(ref leftRef, this.blockHeight - 1); // estimated by bottom-left pixel
-        ref int weights = ref Av1SmoothPredictor.Weights[(int)this.blockHeight];
-
-        int log2Scale = Av1SmoothPredictor.WeightLog2Scale;
-        int scale = 1 << Av1SmoothPredictor.WeightLog2Scale;
-
-        // sm_weights_sanity_checks(sm_weights_w, sm_weights_h, scale, log2_scale + 2);
-        for (nuint r = 0; r < this.blockHeight; ++r)
-        {
-            int rowWeight = Unsafe.Add(ref weights, r);
-            for (nuint c = 0; c < this.blockWidth; ++c)
-            {
-                // The Q8 weight decreases toward the bottom edge, shifting influence from top to bottom-left.
-                int thisPredition = Unsafe.Add(ref aboveRef, c) * rowWeight;
-                thisPredition += belowPrediction * (scale - rowWeight);
-                Unsafe.Add(ref destinationRef, c) = (byte)Av1Math.DivideRound(thisPredition, log2Scale);
-            }
-
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/Av1VerticalPredictor.cs

@@ -1,72 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-using System.Runtime.CompilerServices;
-using SixLabors.ImageSharp.Formats.Heif.Av1.Transform;
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Predicts an 8-bit AV1 block by copying the top neighboring samples into every destination row.
-/// </summary>
-internal readonly struct Av1VerticalPredictor : IAv1Predictor
-{
-    /// <summary>
-    /// The number of top samples consumed and samples written to each destination row.
-    /// </summary>
-    private readonly nuint blockWidth;
-
-    /// <summary>
-    /// The number of destination rows.
-    /// </summary>
-    private readonly nuint blockHeight;
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1VerticalPredictor"/> struct for explicit block dimensions.
-    /// </summary>
-    /// <param name="blockSize">The predicted block dimensions in samples.</param>
-    public Av1VerticalPredictor(Size blockSize)
-    {
-        this.blockWidth = (nuint)blockSize.Width;
-        this.blockHeight = (nuint)blockSize.Height;
-    }
-
-    /// <summary>
-    /// Initializes a new instance of the <see cref="Av1VerticalPredictor"/> struct for a transform size.
-    /// </summary>
-    /// <param name="transformSize">The transform size whose dimensions define the predicted block.</param>
-    public Av1VerticalPredictor(Av1TransformSize transformSize)
-    {
-        this.blockWidth = (nuint)transformSize.GetWidth();
-        this.blockHeight = (nuint)transformSize.GetHeight();
-    }
-
-    /// <summary>
-    /// Predicts a transform block by extending its top edge vertically.
-    /// </summary>
-    /// <param name="transformSize">The predicted block dimensions.</param>
-    /// <param name="destination">The destination block.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The top neighboring samples.</param>
-    /// <param name="left">The unused left-neighbor buffer required by the common predictor signature.</param>
-    public static void PredictScalar(Av1TransformSize transformSize, Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-        => new Av1VerticalPredictor(transformSize).PredictScalar(destination, stride, above, left);
-
-    /// <inheritdoc/>
-    /// <remarks>SVT-AV1: <c>highbd_v_predictor</c>.</remarks>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left)
-    {
-        Guard.MustBeGreaterThanOrEqualTo(stride, this.blockWidth, nameof(stride));
-        Guard.MustBeSizedAtLeast(left, (int)this.blockHeight, nameof(left));
-        Guard.MustBeSizedAtLeast(above, (int)this.blockWidth, nameof(above));
-        Guard.MustBeSizedAtLeast(destination, (int)this.blockHeight * (int)stride, nameof(destination));
-        ref byte aboveRef = ref above[0];
-        ref byte destinationRef = ref destination[0];
-        uint width = (uint)this.blockWidth;
-        for (nuint r = 0; r < this.blockHeight; ++r)
-        {
-            Unsafe.CopyBlock(ref destinationRef, ref aboveRef, width);
-            destinationRef = ref Unsafe.Add(ref destinationRef, stride);
-        }
-    }
-}

src/ImageSharp/Formats/Heif/Av1/Prediction/IAv1Predictor.cs

@@ -1,19 +0,0 @@
-// Copyright (c) Six Labors.
-// Licensed under the Six Labors Split License.
-
-namespace SixLabors.ImageSharp.Formats.Heif.Av1.Prediction;
-
-/// <summary>
-/// Defines scalar reconstruction of an 8-bit AV1 intra-prediction block from its neighboring samples.
-/// </summary>
-internal interface IAv1Predictor
-{
-    /// <summary>
-    /// Writes the predicted block using scalar 8-bit arithmetic.
-    /// </summary>
-    /// <param name="destination">The destination block, starting at its top-left sample.</param>
-    /// <param name="stride">The distance, in samples, between destination rows.</param>
-    /// <param name="above">The neighboring samples immediately above the block.</param>
-    /// <param name="left">The neighboring samples immediately left of the block.</param>
-    public void PredictScalar(Span<byte> destination, nuint stride, Span<byte> above, Span<byte> left);
-}

src/ImageSharp/Formats/Heif/Av1/Transform/Av1BlockDecoder.cs

@@ -52,6 +52,16 @@ internal sealed class Av1BlockDecoder : IDisposable
     /// </summary>
     private readonly IMemoryOwner<int> transformWorkspaceOwner;
 
+    /// <summary>
+    /// Owns the reusable directional and filter-intra prediction workspace.
+    /// </summary>
+    private readonly IMemoryOwner<short> predictionScratchOwner;
+
+    /// <summary>
+    /// Reconstructs intra-predicted blocks using the frame-owned prediction workspace.
+    /// </summary>
+    private readonly Av1PredictionDecoder predictionDecoder;
+
     /// <summary>
     /// Indicates whether transform traversal must also populate loop-filter parameters.
     /// </summary>
@@ -97,6 +107,8 @@ internal sealed class Av1BlockDecoder : IDisposable
 
         this.inverseQuantizationOwner = this.frameBuffer.MemoryAllocator.Allocate<int>(inverseQuantizationSize);
         this.transformWorkspaceOwner = this.frameBuffer.MemoryAllocator.Allocate<int>(Av1TransformWorkspace.MaximumLength);
+        this.predictionScratchOwner = this.frameBuffer.MemoryAllocator.Allocate<short>(Av1PredictionDecoder.ScratchLength);
+        this.predictionDecoder = new(sequenceHeader, frameHeader, this.predictionScratchOwner.Memory);
         this.isLoopFilterEnabled = frameHeader.LoopFilterParameters.FilterLevel[0] != 0 ||
             frameHeader.LoopFilterParameters.FilterLevel[1] != 0;
 
@@ -114,6 +126,7 @@ internal sealed class Av1BlockDecoder : IDisposable
     /// </summary>
     public void Dispose()
     {
+        this.predictionScratchOwner.Dispose();
         this.transformWorkspaceOwner.Dispose();
         this.inverseQuantizationOwner.Dispose();
     }
@@ -184,7 +197,6 @@ internal sealed class Av1BlockDecoder : IDisposable
             : modeInfo.GetTransformUnitCount(Av1Plane.U);
 
         bool highBitDepth = this.frameBuffer.BytesPerSample == 2;
-        Av1PredictionDecoder predictionDecoder = new(this.sequenceHeader, this.frameHeader);
         for (int plane = 0; plane < colorConfig.PlaneCount; plane++)
         {
             int subX = (plane > 0) && colorConfig.SubSamplingX ? 1 : 0;
@@ -277,7 +289,7 @@ internal sealed class Av1BlockDecoder : IDisposable
                 // predicts its samples before any coded residual is added.
                 if (highBitDepth)
                 {
-                    predictionDecoder.Decode(
+                    this.predictionDecoder.Decode(
                         partitionInfo,
                         (Av1Plane)plane,
                         transformSize,
@@ -290,7 +302,7 @@ internal sealed class Av1BlockDecoder : IDisposable
                 }
                 else
                 {
-                    predictionDecoder.Decode(
+                    this.predictionDecoder.Decode(
                         partitionInfo,
                         (Av1Plane)plane,
                         transformSize,