QuantizedFrame<T> using ReadOnlyMemory<T>

src/ImageSharp/Formats/Gif/GifEncoderCore.cs

@@ -233,7 +233,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
             {
                 Span<Rgba32> rgbaSpan = rgbaBuffer.GetSpan();
                 ref Rgba32 paletteRef = ref MemoryMarshal.GetReference(rgbaSpan);
-                PixelOperations<TPixel>.Instance.ToRgba32(this.configuration, quantized.Palette, rgbaSpan);
+                PixelOperations<TPixel>.Instance.ToRgba32(this.configuration, quantized.Palette.Span, rgbaSpan);
 
                 for (int i = quantized.Palette.Length - 1; i >= 0; i--)
                 {
@@ -436,7 +436,7 @@ namespace SixLabors.ImageSharp.Formats.Gif
             {
                 PixelOperations<TPixel>.Instance.ToRgb24Bytes(
                     this.configuration,
-                    image.Palette.AsSpan(),
+                    image.Palette.Span,
                     colorTable.GetSpan(),
                     pixelCount);
                 stream.Write(colorTable.Array, 0, colorTableLength);

src/ImageSharp/Formats/Png/PngEncoderCore.cs

@@ -666,7 +666,7 @@ namespace SixLabors.ImageSharp.Formats.Png
             where TPixel : struct, IPixel<TPixel>
         {
             // Grab the palette and write it to the stream.
-            TPixel[] palette = quantized.Palette;
+            ReadOnlySpan<TPixel> palette = quantized.Palette.Span;
             int paletteLength = Math.Min(palette.Length, 256);
             int colorTableLength = paletteLength * 3;
             bool anyAlpha = false;

src/ImageSharp/Processing/Processors/Quantization/FrameQuantizer{TPixel}.cs

@@ -5,6 +5,7 @@ using System;
 using System.Collections.Generic;
 using System.Numerics;
 using System.Runtime.CompilerServices;
+
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing.Processors.Dithering;
 
@@ -52,7 +53,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             this.Dither = this.Diffuser != null;
             this.singlePass = singlePass;
         }
-        
+
         /// <summary>
         /// Initializes a new instance of the <see cref="FrameQuantizer{TPixel}"/> class.
         /// </summary>
@@ -73,10 +74,15 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         }
 
         /// <inheritdoc />
-        public bool Dither { get; }
+        public IErrorDiffuser Diffuser { get; }
 
         /// <inheritdoc />
-        public IErrorDiffuser Diffuser { get; }
+        public bool Dither { get; }
+
+        /// <inheritdoc/>
+        public virtual void Dispose()
+        {
+        }
 
         /// <inheritdoc/>
         public virtual QuantizedFrame<TPixel> QuantizeFrame(ImageFrame<TPixel> image)
@@ -98,14 +104,13 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             // Collect the palette. Required before the second pass runs.
             ReadOnlyMemory<TPixel> palette = this.GetPalette();
             this.paletteVector = new Vector4[palette.Length];
-            PixelOperations<TPixel>.Instance.ToVector4(image.Configuration, palette.Span, (Span<Vector4>)this.paletteVector, PixelConversionModifiers.Scale);
+            PixelOperations<TPixel>.Instance.ToVector4(
+                image.Configuration,
+                palette.Span,
+                (Span<Vector4>)this.paletteVector,
+                PixelConversionModifiers.Scale);
 
-            // TODO: Pass ReadOnlyMemory<T> instead of array!
-            var quantizedFrame = new QuantizedFrame<TPixel>(
-                image.MemoryAllocator,
-                width,
-                height,
-                palette.Span.ToArray());
+            var quantizedFrame = new QuantizedFrame<TPixel>(image.MemoryAllocator, width, height, palette);
 
             if (this.Dither)
             {
@@ -123,11 +128,6 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
             return quantizedFrame;
         }
 
-        /// <inheritdoc/>
-        public virtual void Dispose()
-        {
-        }
-
         /// <summary>
         /// Execute the first pass through the pixels in the image to create the palette.
         /// </summary>
@@ -139,19 +139,22 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         }
 
         /// <summary>
-        /// Execute a second pass through the image to assign the pixels to a palette entry.
+        /// Returns the closest color from the palette to the given color by calculating the
+        /// Euclidean distance in the Rgba colorspace.
         /// </summary>
-        /// <param name="source">The source image.</param>
-        /// <param name="output">The output pixel array.</param>
-        /// <param name="palette">The output color palette.</param>
-        /// <param name="width">The width in pixels of the image.</param>
-        /// <param name="height">The height in pixels of the image.</param>
-        protected abstract void SecondPass(
-            ImageFrame<TPixel> source,
-            Span<byte> output,
-            ReadOnlySpan<TPixel> palette,
-            int width,
-            int height);
+        /// <param name="pixel">The color.</param>
+        /// <returns>The <see cref="int"/></returns>
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        protected byte GetClosestPixel(ref TPixel pixel)
+        {
+            // Check if the color is in the lookup table
+            if (this.distanceCache.TryGetValue(pixel, out byte value))
+            {
+                return value;
+            }
+
+            return this.GetClosestPixelSlow(ref pixel);
+        }
 
         /// <summary>
         /// Retrieve the palette for the quantized image.
@@ -185,22 +188,19 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         }
 
         /// <summary>
-        /// Returns the closest color from the palette to the given color by calculating the
-        /// Euclidean distance in the Rgba colorspace.
+        /// Execute a second pass through the image to assign the pixels to a palette entry.
         /// </summary>
-        /// <param name="pixel">The color.</param>
-        /// <returns>The <see cref="int"/></returns>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        protected byte GetClosestPixel(ref TPixel pixel)
-        {
-            // Check if the color is in the lookup table
-            if (this.distanceCache.TryGetValue(pixel, out byte value))
-            {
-                return value;
-            }
-
-            return this.GetClosestPixelSlow(ref pixel);
-        }
+        /// <param name="source">The source image.</param>
+        /// <param name="output">The output pixel array.</param>
+        /// <param name="palette">The output color palette.</param>
+        /// <param name="width">The width in pixels of the image.</param>
+        /// <param name="height">The height in pixels of the image.</param>
+        protected abstract void SecondPass(
+            ImageFrame<TPixel> source,
+            Span<byte> output,
+            ReadOnlySpan<TPixel> palette,
+            int width,
+            int height);
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         private byte GetClosestPixelSlow(ref TPixel pixel)

src/ImageSharp/Processing/Processors/Quantization/QuantizeProcessor{TPixel}.cs

@@ -43,12 +43,15 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
                 {
                     Span<TPixel> row = source.GetPixelRowSpan(y);
                     ReadOnlySpan<byte> quantizedPixelSpan = quantized.GetPixelSpan();
+
+                    ReadOnlySpan<TPixel> paletteSpan = quantized.Palette.Span;
+                    
                     int yy = y * source.Width;
 
                     for (int x = 0; x < source.Width; x++)
                     {
                         int i = x + yy;
-                        row[x] = quantized.Palette[Math.Min(paletteCount, quantizedPixelSpan[i])];
+                        row[x] = paletteSpan[Math.Min(paletteCount, quantizedPixelSpan[i])];
                     }
                 }
             }

src/ImageSharp/Processing/Processors/Quantization/QuantizedFrame{TPixel}.cs

@@ -27,7 +27,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <param name="width">The image width.</param>
         /// <param name="height">The image height.</param>
         /// <param name="palette">The color palette.</param>
-        public QuantizedFrame(MemoryAllocator memoryAllocator, int width, int height, TPixel[] palette)
+        public QuantizedFrame(MemoryAllocator memoryAllocator, int width, int height, ReadOnlyMemory<TPixel> palette)
         {
             Guard.MustBeGreaterThan(width, 0, nameof(width));
             Guard.MustBeGreaterThan(height, 0, nameof(height));
@@ -51,7 +51,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Quantization
         /// <summary>
         /// Gets the color palette of this <see cref="QuantizedFrame{TPixel}"/>.
         /// </summary>
-        public TPixel[] Palette { get; private set; }
+        public ReadOnlyMemory<TPixel> Palette { get; private set; }
 
         /// <summary>
         /// Gets the pixels of this <see cref="QuantizedFrame{TPixel}"/>.

tests/ImageSharp.Tests/Quantization/QuantizedImageTests.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors and contributors.
 // Licensed under the Apache License, Version 2.0.
 
+using System;
+
 using SixLabors.ImageSharp.PixelFormats;
 using SixLabors.ImageSharp.Processing.Processors.Quantization;
 
@@ -85,9 +87,10 @@ namespace SixLabors.ImageSharp.Tests
             // Transparent pixels are much more likely to be found at the end of a palette
             int index = -1;
             Rgba32 trans = default;
-            for (int i = quantized.Palette.Length - 1; i >= 0; i--)
+            ReadOnlySpan<TPixel> paletteSpan = quantized.Palette.Span;
+            for (int i = paletteSpan.Length - 1; i >= 0; i--)
             {
-                quantized.Palette[i].ToRgba32(ref trans);
+                paletteSpan[i].ToRgba32(ref trans);
 
                 if (trans.Equals(default))
                 {

tests/ImageSharp.Tests/Quantization/WuQuantizerTests.cs

@@ -20,7 +20,7 @@ namespace SixLabors.ImageSharp.Tests.Quantization
                 Assert.Equal(1, result.Palette.Length);
                 Assert.Equal(1, result.GetPixelSpan().Length);
 
-                Assert.Equal(Rgba32.Black, result.Palette[0]);
+                Assert.Equal(Rgba32.Black, result.Palette.Span[0]);
                 Assert.Equal(0, result.GetPixelSpan()[0]);
             }
         }
@@ -37,7 +37,7 @@ namespace SixLabors.ImageSharp.Tests.Quantization
                 Assert.Equal(1, result.Palette.Length);
                 Assert.Equal(1, result.GetPixelSpan().Length);
 
-                Assert.Equal(default, result.Palette[0]);
+                Assert.Equal(default, result.Palette.Span[0]);
                 Assert.Equal(0, result.GetPixelSpan()[0]);
             }
         }
@@ -82,6 +82,7 @@ namespace SixLabors.ImageSharp.Tests.Quantization
 
                     var actualImage = new Image<Rgba32>(1, 256);
 
+                    ReadOnlySpan<Rgba32> paletteSpan = result.Palette.Span;
                     int paletteCount = result.Palette.Length - 1;
                     for (int y = 0; y < actualImage.Height; y++)
                     {
@@ -92,7 +93,7 @@ namespace SixLabors.ImageSharp.Tests.Quantization
                         for (int x = 0; x < actualImage.Width; x++)
                         {
                             int i = x + yy;
-                            row[x] = result.Palette[Math.Min(paletteCount, quantizedPixelSpan[i])];
+                            row[x] = paletteSpan[Math.Min(paletteCount, quantizedPixelSpan[i])];
                         }
                     }
 
@@ -146,6 +147,7 @@ namespace SixLabors.ImageSharp.Tests.Quantization
                     Assert.Equal(4 * 8, result.Palette.Length);
                     Assert.Equal(256, result.GetPixelSpan().Length);
 
+                    ReadOnlySpan<Rgba32> paletteSpan = result.Palette.Span;
                     int paletteCount = result.Palette.Length - 1;
                     for (int y = 0; y < actualImage.Height; y++)
                     {
@@ -156,7 +158,7 @@ namespace SixLabors.ImageSharp.Tests.Quantization
                         for (int x = 0; x < actualImage.Width; x++)
                         {
                             int i = x + yy;
-                            row[x] = result.Palette[Math.Min(paletteCount, quantizedPixelSpan[i])];
+                            row[x] = paletteSpan[Math.Min(paletteCount, quantizedPixelSpan[i])];
                         }
                     }
                 }