Preparation

src/ImageSharp/Formats/Webp/AlphaEncoder.cs

@@ -19,7 +19,7 @@ internal static class AlphaEncoder
     /// Data is either compressed as lossless webp image or uncompressed.
     /// </summary>
     /// <typeparam name="TPixel">The pixel format.</typeparam>
-    /// <param name="image">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
+    /// <param name="frame">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
     /// <param name="configuration">The global configuration.</param>
     /// <param name="memoryAllocator">The memory manager.</param>
     /// <param name="skipMetadata">Whether to skip metadata encoding.</param>
@@ -27,7 +27,7 @@ internal static class AlphaEncoder
     /// <param name="size">The size in bytes of the alpha data.</param>
     /// <returns>The encoded alpha data.</returns>
     public static IMemoryOwner<byte> EncodeAlpha<TPixel>(
-        Image<TPixel> image,
+        ImageFrame<TPixel> frame,
         Configuration configuration,
         MemoryAllocator memoryAllocator,
         bool skipMetadata,
@@ -35,9 +35,9 @@ internal static class AlphaEncoder
         out int size)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        int width = image.Width;
-        int height = image.Height;
-        IMemoryOwner<byte> alphaData = ExtractAlphaChannel(image, configuration, memoryAllocator);
+        int width = frame.Width;
+        int height = frame.Height;
+        IMemoryOwner<byte> alphaData = ExtractAlphaChannel(frame, configuration, memoryAllocator);
 
         if (compress)
         {
@@ -58,9 +58,9 @@ internal static class AlphaEncoder
             // The transparency information will be stored in the green channel of the ARGB quadruplet.
             // The green channel is allowed extra transformation steps in the specification -- unlike the other channels,
             // that can improve compression.
-            using Image<Rgba32> alphaAsImage = DispatchAlphaToGreen(image, alphaData.GetSpan());
+            using ImageFrame<Rgba32> alphaAsFrame = DispatchAlphaToGreen(frame, alphaData.GetSpan());
 
-            size = lossLessEncoder.EncodeAlphaImageData(alphaAsImage, alphaData);
+            size = lossLessEncoder.EncodeAlphaImageData(alphaAsFrame, alphaData);
 
             return alphaData;
         }
@@ -73,45 +73,45 @@ internal static class AlphaEncoder
     /// Store the transparency in the green channel.
     /// </summary>
     /// <typeparam name="TPixel">The pixel format.</typeparam>
-    /// <param name="image">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
+    /// <param name="frame">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
     /// <param name="alphaData">A byte sequence of length width * height, containing all the 8-bit transparency values in scan order.</param>
-    /// <returns>The transparency image.</returns>
-    private static Image<Rgba32> DispatchAlphaToGreen<TPixel>(Image<TPixel> image, Span<byte> alphaData)
+    /// <returns>The transparency frame.</returns>
+    private static ImageFrame<Rgba32> DispatchAlphaToGreen<TPixel>(ImageFrame<TPixel> frame, Span<byte> alphaData)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        int width = image.Width;
-        int height = image.Height;
-        Image<Rgba32> alphaAsImage = new(width, height);
+        int width = frame.Width;
+        int height = frame.Height;
+        ImageFrame<Rgba32> alphaAsFrame = new(Configuration.Default, width, height);
 
         for (int y = 0; y < height; y++)
         {
-            Memory<Rgba32> rowBuffer = alphaAsImage.DangerousGetPixelRowMemory(y);
+            Memory<Rgba32> rowBuffer = alphaAsFrame.DangerousGetPixelRowMemory(y);
             Span<Rgba32> pixelRow = rowBuffer.Span;
             Span<byte> alphaRow = alphaData.Slice(y * width, width);
             for (int x = 0; x < width; x++)
             {
                 // Leave A/R/B channels zero'd.
-                pixelRow[x] = new Rgba32(0, alphaRow[x], 0, 0);
+                pixelRow[x] = new(0, alphaRow[x], 0, 0);
             }
         }
 
-        return alphaAsImage;
+        return alphaAsFrame;
     }
 
     /// <summary>
     /// Extract the alpha data of the image.
     /// </summary>
     /// <typeparam name="TPixel">The pixel format.</typeparam>
-    /// <param name="image">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
+    /// <param name="frame">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
     /// <param name="configuration">The global configuration.</param>
     /// <param name="memoryAllocator">The memory manager.</param>
     /// <returns>A byte sequence of length width * height, containing all the 8-bit transparency values in scan order.</returns>
-    private static IMemoryOwner<byte> ExtractAlphaChannel<TPixel>(Image<TPixel> image, Configuration configuration, MemoryAllocator memoryAllocator)
+    private static IMemoryOwner<byte> ExtractAlphaChannel<TPixel>(ImageFrame<TPixel> frame, Configuration configuration, MemoryAllocator memoryAllocator)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        Buffer2D<TPixel> imageBuffer = image.Frames.RootFrame.PixelBuffer;
-        int height = image.Height;
-        int width = image.Width;
+        Buffer2D<TPixel> imageBuffer = frame.PixelBuffer;
+        int height = frame.Height;
+        int width = frame.Width;
         IMemoryOwner<byte> alphaDataBuffer = memoryAllocator.Allocate<byte>(width * height);
         Span<byte> alphaData = alphaDataBuffer.GetSpan();
 

src/ImageSharp/Formats/Webp/AnimationFrameData.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
 
+using SixLabors.ImageSharp.IO;
+
 namespace SixLabors.ImageSharp.Formats.Webp;
 
 internal struct AnimationFrameData
@@ -10,6 +12,11 @@ internal struct AnimationFrameData
     /// </summary>
     public uint DataSize;
 
+    /// <summary>
+    /// X(3) + Y(3) + Width(3) + Height(3) + Duration(3) + 1 byte for flags.
+    /// </summary>
+    public const uint HeaderSize = 16;
+
     /// <summary>
     /// The X coordinate of the upper left corner of the frame is Frame X * 2.
     /// </summary>
@@ -45,4 +52,40 @@ internal struct AnimationFrameData
     /// Indicates how the current frame is to be treated after it has been displayed (before rendering the next frame) on the canvas.
     /// </summary>
     public AnimationDisposalMethod DisposalMethod;
+
+    /// <summary>
+    /// Reads the animation frame header.
+    /// </summary>
+    /// <param name="stream">The stream to read from.</param>
+    /// <returns>Animation frame data.</returns>
+    public static AnimationFrameData Parse(BufferedReadStream stream)
+    {
+        Span<byte> buffer = stackalloc byte[4];
+
+        AnimationFrameData data = new()
+        {
+            DataSize = WebpChunkParsingUtils.ReadChunkSize(stream, buffer),
+
+            // 3 bytes for the X coordinate of the upper left corner of the frame.
+            X = WebpChunkParsingUtils.ReadUInt24LittleEndian(stream, buffer),
+
+            // 3 bytes for the Y coordinate of the upper left corner of the frame.
+            Y = WebpChunkParsingUtils.ReadUInt24LittleEndian(stream, buffer),
+
+            // Frame width Minus One.
+            Width = WebpChunkParsingUtils.ReadUInt24LittleEndian(stream, buffer) + 1,
+
+            // Frame height Minus One.
+            Height = WebpChunkParsingUtils.ReadUInt24LittleEndian(stream, buffer) + 1,
+
+            // Frame duration.
+            Duration = WebpChunkParsingUtils.ReadUInt24LittleEndian(stream, buffer)
+        };
+
+        byte flags = (byte)stream.ReadByte();
+        data.DisposalMethod = (flags & 1) == 1 ? AnimationDisposalMethod.Dispose : AnimationDisposalMethod.DoNotDispose;
+        data.BlendingMethod = (flags & (1 << 1)) != 0 ? AnimationBlendingMethod.DoNotBlend : AnimationBlendingMethod.AlphaBlending;
+
+        return data;
+    }
 }

src/ImageSharp/Formats/Webp/BitWriter/BitWriterBase.cs

@@ -2,6 +2,7 @@
 // Licensed under the Six Labors Split License.
 
 using System.Buffers.Binary;
+using System.Drawing;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Metadata.Profiles.Exif;
 using SixLabors.ImageSharp.Metadata.Profiles.Xmp;
@@ -92,7 +93,7 @@ internal abstract class BitWriterBase
     {
         stream.Write(WebpConstants.RiffFourCc);
         BinaryPrimitives.WriteUInt32LittleEndian(this.scratchBuffer.Span, riffSize);
-        stream.Write(this.scratchBuffer.Span.Slice(0, 4));
+        stream.Write(this.scratchBuffer.Span[..4]);
         stream.Write(WebpConstants.WebpHeader);
     }
 
@@ -129,7 +130,7 @@ internal abstract class BitWriterBase
         DebugGuard.NotNull(metadataBytes, nameof(metadataBytes));
 
         uint size = (uint)metadataBytes.Length;
-        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
+        Span<byte> buf = this.scratchBuffer.Span[..4];
         BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)chunkType);
         stream.Write(buf);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
@@ -143,6 +144,61 @@ internal abstract class BitWriterBase
         }
     }
 
+    /// <summary>
+    /// Writes the color profile(<see cref="WebpChunkType.Iccp"/>) to the stream.
+    /// </summary>
+    /// <param name="stream">The stream to write to.</param>
+    /// <param name="iccProfileBytes">The color profile bytes.</param>
+    protected void WriteColorProfile(Stream stream, byte[] iccProfileBytes) => this.WriteMetadataProfile(stream, iccProfileBytes, WebpChunkType.Iccp);
+
+    /// <summary>
+    /// Writes the animation parameter(<see cref="WebpChunkType.AnimationParameter"/>) to the stream.
+    /// </summary>
+    /// <param name="stream">The stream to write to.</param>
+    /// <param name="background">
+    /// The default background color of the canvas in [Blue, Green, Red, Alpha] byte order.
+    /// This color MAY be used to fill the unused space on the canvas around the frames,
+    /// as well as the transparent pixels of the first frame.
+    /// The background color is also used when the Disposal method is 1.
+    /// </param>
+    /// <param name="loopCount">The number of times to loop the animation. If it is 0, this means infinitely.</param>
+    protected void WriteAnimationParameter(Stream stream, uint background, ushort loopCount)
+    {
+        Span<byte> buf = this.scratchBuffer.Span[..4];
+        BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.AnimationParameter);
+        stream.Write(buf);
+        BinaryPrimitives.WriteUInt32LittleEndian(buf, sizeof(uint) + sizeof(ushort));
+        stream.Write(buf);
+        BinaryPrimitives.WriteUInt32LittleEndian(buf, background);
+        stream.Write(buf);
+        BinaryPrimitives.WriteUInt16LittleEndian(buf[..2], loopCount);
+        stream.Write(buf[..2]);
+    }
+
+    /// <summary>
+    /// Writes the animation frame(<see cref="WebpChunkType.Animation"/>) to the stream.
+    /// </summary>
+    /// <param name="stream">The stream to write to.</param>
+    /// <param name="animation">Animation frame data.</param>
+    /// <param name="data">Frame data.</param>
+    protected void WriteAnimationFrame(Stream stream, AnimationFrameData animation, byte[] data)
+    {
+        uint size = AnimationFrameData.HeaderSize + (uint)data.Length;
+        Span<byte> buf = this.scratchBuffer.Span[..4];
+        BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Animation);
+        stream.Write(buf);
+        BinaryPrimitives.WriteUInt32BigEndian(buf, size);
+        stream.Write(buf);
+        WebpChunkParsingUtils.WriteUInt24LittleEndian(stream, animation.X);
+        WebpChunkParsingUtils.WriteUInt24LittleEndian(stream, animation.Y);
+        WebpChunkParsingUtils.WriteUInt24LittleEndian(stream, animation.Width - 1);
+        WebpChunkParsingUtils.WriteUInt24LittleEndian(stream, animation.Height - 1);
+        WebpChunkParsingUtils.WriteUInt24LittleEndian(stream, animation.Duration);
+        byte flag = (byte)(((int)animation.BlendingMethod << 1) | (int)animation.DisposalMethod);
+        stream.WriteByte(flag);
+        stream.Write(data);
+    }
+
     /// <summary>
     /// Writes the alpha chunk to the stream.
     /// </summary>
@@ -152,7 +208,7 @@ internal abstract class BitWriterBase
     protected void WriteAlphaChunk(Stream stream, Span<byte> dataBytes, bool alphaDataIsCompressed)
     {
         uint size = (uint)dataBytes.Length + 1;
-        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
+        Span<byte> buf = this.scratchBuffer.Span[..4];
         BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Alpha);
         stream.Write(buf);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
@@ -161,7 +217,7 @@ internal abstract class BitWriterBase
         byte flags = 0;
         if (alphaDataIsCompressed)
         {
-            flags |= 1;
+            flags = 1;
         }
 
         stream.WriteByte(flags);
@@ -174,30 +230,6 @@ internal abstract class BitWriterBase
         }
     }
 
-    /// <summary>
-    /// Writes the color profile to the stream.
-    /// </summary>
-    /// <param name="stream">The stream to write to.</param>
-    /// <param name="iccProfileBytes">The color profile bytes.</param>
-    protected void WriteColorProfile(Stream stream, byte[] iccProfileBytes)
-    {
-        uint size = (uint)iccProfileBytes.Length;
-
-        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
-        BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Iccp);
-        stream.Write(buf);
-        BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
-        stream.Write(buf);
-
-        stream.Write(iccProfileBytes);
-
-        // Add padding byte if needed.
-        if ((size & 1) == 1)
-        {
-            stream.WriteByte(0);
-        }
-    }
-
     /// <summary>
     /// Writes a VP8X header to the stream.
     /// </summary>
@@ -246,8 +278,9 @@ internal abstract class BitWriterBase
             flags |= 32;
         }
 
-        Span<byte> buf = this.scratchBuffer.Span.Slice(0, 4);
-        stream.Write(WebpConstants.Vp8XMagicBytes);
+        Span<byte> buf = this.scratchBuffer.Span[..4];
+        BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Vp8X);
+        stream.Write(buf);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, WebpConstants.Vp8XChunkSize);
         stream.Write(buf);
         BinaryPrimitives.WriteUInt32LittleEndian(buf, flags);

src/ImageSharp/Formats/Webp/BitWriter/Vp8BitWriter.cs

@@ -701,12 +701,11 @@ internal class Vp8BitWriter : BitWriterBase
 
     private void WriteVp8Header(Stream stream, uint size)
     {
-        Span<byte> vp8ChunkHeader = stackalloc byte[WebpConstants.ChunkHeaderSize];
-
-        WebpConstants.Vp8MagicBytes.AsSpan().CopyTo(vp8ChunkHeader);
-        BinaryPrimitives.WriteUInt32LittleEndian(vp8ChunkHeader[4..], size);
-
-        stream.Write(vp8ChunkHeader);
+        Span<byte> buf = stackalloc byte[WebpConstants.TagSize];
+        BinaryPrimitives.WriteUInt32BigEndian(buf, (uint)WebpChunkType.Vp8);
+        stream.Write(buf);
+        BinaryPrimitives.WriteUInt32LittleEndian(buf, size);
+        stream.Write(buf);
     }
 
     private void WriteFrameHeader(Stream stream, uint size0)

src/ImageSharp/Formats/Webp/BitWriter/Vp8LBitWriter.cs

@@ -105,7 +105,7 @@ internal class Vp8LBitWriter : BitWriterBase
     {
         byte[] clonedBuffer = new byte[this.Buffer.Length];
         System.Buffer.BlockCopy(this.Buffer, 0, clonedBuffer, 0, this.cur);
-        return new Vp8LBitWriter(clonedBuffer, this.bits, this.used, this.cur);
+        return new(clonedBuffer, this.bits, this.used, this.cur);
     }
 
     /// <inheritdoc/>
@@ -186,12 +186,13 @@ internal class Vp8LBitWriter : BitWriterBase
         }
 
         // Write magic bytes indicating its a lossless webp.
-        stream.Write(WebpConstants.Vp8LMagicBytes);
+        Span<byte> scratchBuffer = stackalloc byte[WebpConstants.TagSize];
+        BinaryPrimitives.WriteUInt32BigEndian(scratchBuffer, (uint)WebpChunkType.Vp8L);
+        stream.Write(scratchBuffer);
 
         // Write Vp8 Header.
-        Span<byte> scratchBuffer = stackalloc byte[8];
         BinaryPrimitives.WriteUInt32LittleEndian(scratchBuffer, size);
-        stream.Write(scratchBuffer.Slice(0, 4));
+        stream.Write(scratchBuffer);
         stream.WriteByte(WebpConstants.Vp8LHeaderMagicByte);
 
         // Write the encoded bytes of the image to the stream.
@@ -226,7 +227,7 @@ internal class Vp8LBitWriter : BitWriterBase
 
         Span<byte> scratchBuffer = stackalloc byte[8];
         BinaryPrimitives.WriteUInt64LittleEndian(scratchBuffer, this.bits);
-        scratchBuffer.Slice(0, 4).CopyTo(this.Buffer.AsSpan(this.cur));
+        scratchBuffer[..4].CopyTo(this.Buffer.AsSpan(this.cur));
 
         this.cur += WriterBytes;
         this.bits >>= WriterBits;

src/ImageSharp/Formats/Webp/Lossless/Vp8LEncoder.cs

@@ -254,7 +254,7 @@ internal class Vp8LEncoder : IDisposable
         XmpProfile xmpProfile = this.skipMetadata ? null : metadata.XmpProfile;
 
         // Convert image pixels to bgra array.
-        bool hasAlpha = this.ConvertPixelsToBgra(image, width, height);
+        bool hasAlpha = this.ConvertPixelsToBgra(image.Frames.RootFrame, width, height);
 
         // Write the image size.
         this.WriteImageSize(width, height);
@@ -263,7 +263,7 @@ internal class Vp8LEncoder : IDisposable
         this.WriteAlphaAndVersion(hasAlpha);
 
         // Encode the main image stream.
-        this.EncodeStream(image);
+        this.EncodeStream(image.Frames.RootFrame);
 
         // Write bytes from the bitwriter buffer to the stream.
         this.bitWriter.WriteEncodedImageToStream(stream, exifProfile, xmpProfile, metadata.IccProfile, (uint)width, (uint)height, hasAlpha);
@@ -273,23 +273,23 @@ internal class Vp8LEncoder : IDisposable
     /// Encodes the alpha image data using the webp lossless compression.
     /// </summary>
     /// <typeparam name="TPixel">The type of the pixel.</typeparam>
-    /// <param name="image">The <see cref="Image{TPixel}"/> to encode from.</param>
+    /// <param name="frame">The <see cref="ImageFrame{TPixel}"/> to encode from.</param>
     /// <param name="alphaData">The destination buffer to write the encoded alpha data to.</param>
     /// <returns>The size of the compressed data in bytes.
     /// If the size of the data is the same as the pixel count, the compression would not yield in smaller data and is left uncompressed.
     /// </returns>
-    public int EncodeAlphaImageData<TPixel>(Image<TPixel> image, IMemoryOwner<byte> alphaData)
+    public int EncodeAlphaImageData<TPixel>(ImageFrame<TPixel> frame, IMemoryOwner<byte> alphaData)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        int width = image.Width;
-        int height = image.Height;
+        int width = frame.Width;
+        int height = frame.Height;
         int pixelCount = width * height;
 
         // Convert image pixels to bgra array.
-        this.ConvertPixelsToBgra(image, width, height);
+        this.ConvertPixelsToBgra(frame, width, height);
 
         // The image-stream will NOT contain any headers describing the image dimension, the dimension is already known.
-        this.EncodeStream(image);
+        this.EncodeStream(frame);
         this.bitWriter.Finish();
         int size = this.bitWriter.NumBytes();
         if (size >= pixelCount)
@@ -333,12 +333,12 @@ internal class Vp8LEncoder : IDisposable
     /// Encodes the image stream using lossless webp format.
     /// </summary>
     /// <typeparam name="TPixel">The pixel type.</typeparam>
-    /// <param name="image">The image to encode.</param>
-    private void EncodeStream<TPixel>(Image<TPixel> image)
+    /// <param name="frame">The frame to encode.</param>
+    private void EncodeStream<TPixel>(ImageFrame<TPixel> frame)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        int width = image.Width;
-        int height = image.Height;
+        int width = frame.Width;
+        int height = frame.Height;
 
         Span<uint> bgra = this.Bgra.GetSpan();
         Span<uint> encodedData = this.EncodedData.GetSpan();
@@ -447,14 +447,14 @@ internal class Vp8LEncoder : IDisposable
     /// Converts the pixels of the image to bgra.
     /// </summary>
     /// <typeparam name="TPixel">The type of the pixels.</typeparam>
-    /// <param name="image">The image to convert.</param>
+    /// <param name="frame">The frame to convert.</param>
     /// <param name="width">The width of the image.</param>
     /// <param name="height">The height of the image.</param>
     /// <returns>true, if the image is non opaque.</returns>
-    private bool ConvertPixelsToBgra<TPixel>(Image<TPixel> image, int width, int height)
+    private bool ConvertPixelsToBgra<TPixel>(ImageFrame<TPixel> frame, int width, int height)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        Buffer2D<TPixel> imageBuffer = image.Frames.RootFrame.PixelBuffer;
+        Buffer2D<TPixel> imageBuffer = frame.PixelBuffer;
         bool nonOpaque = false;
         Span<uint> bgra = this.Bgra.GetSpan();
         Span<byte> bgraBytes = MemoryMarshal.Cast<uint, byte>(bgra);
@@ -1149,35 +1149,41 @@ internal class Vp8LEncoder : IDisposable
             entropyComp[j] = bitEntropy.BitsEntropyRefine();
         }
 
-        entropy[(int)EntropyIx.Direct] = entropyComp[(int)HistoIx.HistoAlpha] +
-                                         entropyComp[(int)HistoIx.HistoRed] +
-                                         entropyComp[(int)HistoIx.HistoGreen] +
-                                         entropyComp[(int)HistoIx.HistoBlue];
-        entropy[(int)EntropyIx.Spatial] = entropyComp[(int)HistoIx.HistoAlphaPred] +
-                                          entropyComp[(int)HistoIx.HistoRedPred] +
-                                          entropyComp[(int)HistoIx.HistoGreenPred] +
-                                          entropyComp[(int)HistoIx.HistoBluePred];
-        entropy[(int)EntropyIx.SubGreen] = entropyComp[(int)HistoIx.HistoAlpha] +
-                                           entropyComp[(int)HistoIx.HistoRedSubGreen] +
-                                           entropyComp[(int)HistoIx.HistoGreen] +
-                                           entropyComp[(int)HistoIx.HistoBlueSubGreen];
-        entropy[(int)EntropyIx.SpatialSubGreen] = entropyComp[(int)HistoIx.HistoAlphaPred] +
-                                                  entropyComp[(int)HistoIx.HistoRedPredSubGreen] +
-                                                  entropyComp[(int)HistoIx.HistoGreenPred] +
-                                                  entropyComp[(int)HistoIx.HistoBluePredSubGreen];
+        entropy[(int)EntropyIx.Direct] =
+            entropyComp[(int)HistoIx.HistoAlpha] +
+            entropyComp[(int)HistoIx.HistoRed] +
+            entropyComp[(int)HistoIx.HistoGreen] +
+            entropyComp[(int)HistoIx.HistoBlue];
+        entropy[(int)EntropyIx.Spatial] =
+            entropyComp[(int)HistoIx.HistoAlphaPred] +
+            entropyComp[(int)HistoIx.HistoRedPred] +
+            entropyComp[(int)HistoIx.HistoGreenPred] +
+            entropyComp[(int)HistoIx.HistoBluePred];
+        entropy[(int)EntropyIx.SubGreen] =
+            entropyComp[(int)HistoIx.HistoAlpha] +
+            entropyComp[(int)HistoIx.HistoRedSubGreen] +
+            entropyComp[(int)HistoIx.HistoGreen] +
+            entropyComp[(int)HistoIx.HistoBlueSubGreen];
+        entropy[(int)EntropyIx.SpatialSubGreen] =
+            entropyComp[(int)HistoIx.HistoAlphaPred] +
+            entropyComp[(int)HistoIx.HistoRedPredSubGreen] +
+            entropyComp[(int)HistoIx.HistoGreenPred] +
+            entropyComp[(int)HistoIx.HistoBluePredSubGreen];
         entropy[(int)EntropyIx.Palette] = entropyComp[(int)HistoIx.HistoPalette];
 
         // When including transforms, there is an overhead in bits from
         // storing them. This overhead is small but matters for small images.
         // For spatial, there are 14 transformations.
-        entropy[(int)EntropyIx.Spatial] += LosslessUtils.SubSampleSize(width, transformBits) *
-                                           LosslessUtils.SubSampleSize(height, transformBits) *
-                                           LosslessUtils.FastLog2(14);
+        entropy[(int)EntropyIx.Spatial] +=
+            LosslessUtils.SubSampleSize(width, transformBits) *
+            LosslessUtils.SubSampleSize(height, transformBits) *
+            LosslessUtils.FastLog2(14);
 
         // For color transforms: 24 as only 3 channels are considered in a ColorTransformElement.
-        entropy[(int)EntropyIx.SpatialSubGreen] += LosslessUtils.SubSampleSize(width, transformBits) *
-                                                   LosslessUtils.SubSampleSize(height, transformBits) *
-                                                   LosslessUtils.FastLog2(24);
+        entropy[(int)EntropyIx.SpatialSubGreen] +=
+            LosslessUtils.SubSampleSize(width, transformBits) *
+            LosslessUtils.SubSampleSize(height, transformBits) *
+            LosslessUtils.FastLog2(24);
 
         // For palettes, add the cost of storing the palette.
         // We empirically estimate the cost of a compressed entry as 8 bits.

src/ImageSharp/Formats/Webp/Lossy/Vp8Encoder.cs

@@ -323,7 +323,7 @@ internal class Vp8Encoder : IDisposable
         Span<byte> y = this.Y.GetSpan();
         Span<byte> u = this.U.GetSpan();
         Span<byte> v = this.V.GetSpan();
-        bool hasAlpha = YuvConversion.ConvertRgbToYuv(image, this.configuration, this.memoryAllocator, y, u, v);
+        bool hasAlpha = YuvConversion.ConvertRgbToYuv(image.Frames.RootFrame, this.configuration, this.memoryAllocator, y, u, v);
 
         int yStride = width;
         int uvStride = (yStride + 1) >> 1;
@@ -393,7 +393,7 @@ internal class Vp8Encoder : IDisposable
             {
                 // TODO: This can potentially run in an separate task.
                 encodedAlphaData = AlphaEncoder.EncodeAlpha(
-                    image,
+                    image.Frames.RootFrame,
                     this.configuration,
                     this.memoryAllocator,
                     this.skipMetadata,

src/ImageSharp/Formats/Webp/Lossy/YuvConversion.cs

@@ -262,17 +262,17 @@ internal static class YuvConversion
     /// Converts the RGB values of the image to YUV.
     /// </summary>
     /// <typeparam name="TPixel">The pixel type of the image.</typeparam>
-    /// <param name="image">The image to convert.</param>
+    /// <param name="frame">The frame to convert.</param>
     /// <param name="configuration">The global configuration.</param>
     /// <param name="memoryAllocator">The memory allocator.</param>
     /// <param name="y">Span to store the luma component of the image.</param>
     /// <param name="u">Span to store the u component of the image.</param>
     /// <param name="v">Span to store the v component of the image.</param>
     /// <returns>true, if the image contains alpha data.</returns>
-    public static bool ConvertRgbToYuv<TPixel>(Image<TPixel> image, Configuration configuration, MemoryAllocator memoryAllocator, Span<byte> y, Span<byte> u, Span<byte> v)
+    public static bool ConvertRgbToYuv<TPixel>(ImageFrame<TPixel> frame, Configuration configuration, MemoryAllocator memoryAllocator, Span<byte> y, Span<byte> u, Span<byte> v)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        Buffer2D<TPixel> imageBuffer = image.Frames.RootFrame.PixelBuffer;
+        Buffer2D<TPixel> imageBuffer = frame.PixelBuffer;
         int width = imageBuffer.Width;
         int height = imageBuffer.Height;
         int uvWidth = (width + 1) >> 1;

src/ImageSharp/Formats/Webp/WebpAnimationDecoder.cs

@@ -138,7 +138,7 @@ internal class WebpAnimationDecoder : IDisposable
     private uint ReadFrame<TPixel>(BufferedReadStream stream, ref Image<TPixel>? image, ref ImageFrame<TPixel>? previousFrame, uint width, uint height, Color backgroundColor)
         where TPixel : unmanaged, IPixel<TPixel>
     {
-        AnimationFrameData frameData = this.ReadFrameHeader(stream);
+        AnimationFrameData frameData = AnimationFrameData.Parse(stream);
         long streamStartPosition = stream.Position;
         Span<byte> buffer = stackalloc byte[4];
 
@@ -173,7 +173,7 @@ internal class WebpAnimationDecoder : IDisposable
         ImageFrame<TPixel> imageFrame;
         if (previousFrame is null)
         {
-            image = new Image<TPixel>(this.configuration, (int)width, (int)height, backgroundColor.ToPixel<TPixel>(), this.metadata);
+            image = new(this.configuration, (int)width, (int)height, backgroundColor.ToPixel<TPixel>(), this.metadata);
 
             SetFrameMetadata(image.Frames.RootFrame.Metadata, frameData.Duration);
 
@@ -258,7 +258,7 @@ internal class WebpAnimationDecoder : IDisposable
 
         try
         {
-            Buffer2D<TPixel> pixelBufferDecoded = decodedImage.Frames.RootFrame.PixelBuffer;
+            Buffer2D<TPixel> pixelBufferDecoded = decodedImage.GetRootFramePixelBuffer();
             if (webpInfo.IsLossless)
             {
                 WebpLosslessDecoder losslessDecoder = new(webpInfo.Vp8LBitReader, this.memoryAllocator, this.configuration);
@@ -353,42 +353,6 @@ internal class WebpAnimationDecoder : IDisposable
         pixelRegion.Fill(backgroundPixel);
     }
 
-    /// <summary>
-    /// Reads the animation frame header.
-    /// </summary>
-    /// <param name="stream">The stream to read from.</param>
-    /// <returns>Animation frame data.</returns>
-    private AnimationFrameData ReadFrameHeader(BufferedReadStream stream)
-    {
-        Span<byte> buffer = stackalloc byte[4];
-
-        AnimationFrameData data = new()
-        {
-            DataSize = WebpChunkParsingUtils.ReadChunkSize(stream, buffer),
-
-            // 3 bytes for the X coordinate of the upper left corner of the frame.
-            X = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer),
-
-            // 3 bytes for the Y coordinate of the upper left corner of the frame.
-            Y = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer),
-
-            // Frame width Minus One.
-            Width = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer) + 1,
-
-            // Frame height Minus One.
-            Height = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer) + 1,
-
-            // Frame duration.
-            Duration = WebpChunkParsingUtils.ReadUnsignedInt24Bit(stream, buffer)
-        };
-
-        byte flags = (byte)stream.ReadByte();
-        data.DisposalMethod = (flags & 1) == 1 ? AnimationDisposalMethod.Dispose : AnimationDisposalMethod.DoNotDispose;
-        data.BlendingMethod = (flags & (1 << 1)) != 0 ? AnimationBlendingMethod.DoNotBlend : AnimationBlendingMethod.AlphaBlending;
-
-        return data;
-    }
-
     /// <inheritdoc/>
     public void Dispose() => this.alphaData?.Dispose();
 }

src/ImageSharp/Formats/Webp/WebpAnimationEncoder.cs

@@ -0,0 +1,12 @@
+// Copyright (c) Six Labors.
+// Licensed under the Six Labors Split License.
+
+namespace SixLabors.ImageSharp.Formats.Webp;
+
+/// <summary>
+/// Encoder for animated webp images.
+/// </summary>
+public class WebpAnimationEncoder
+{
+    // 可能不需要这个屌东西
+}

src/ImageSharp/Formats/Webp/WebpChunkParsingUtils.cs

@@ -2,13 +2,12 @@
 // Licensed under the Six Labors Split License.
 
 using System.Buffers.Binary;
+using System.Drawing;
 using SixLabors.ImageSharp.Formats.Webp.BitReader;
 using SixLabors.ImageSharp.Formats.Webp.Lossy;
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
 using SixLabors.ImageSharp.Metadata;
-using SixLabors.ImageSharp.Metadata.Profiles.Exif;
-using SixLabors.ImageSharp.Metadata.Profiles.Xmp;
 
 namespace SixLabors.ImageSharp.Formats.Webp;
 
@@ -91,7 +90,7 @@ internal static class WebpChunkParsingUtils
         uint tmp = BinaryPrimitives.ReadUInt16LittleEndian(buffer);
         uint width = tmp & 0x3fff;
         sbyte xScale = (sbyte)(tmp >> 6);
-        tmp = BinaryPrimitives.ReadUInt16LittleEndian(buffer.Slice(2));
+        tmp = BinaryPrimitives.ReadUInt16LittleEndian(buffer[2..]);
         uint height = tmp & 0x3fff;
         sbyte yScale = (sbyte)(tmp >> 6);
         remaining -= 7;
@@ -105,14 +104,14 @@ internal static class WebpChunkParsingUtils
             WebpThrowHelper.ThrowImageFormatException("bad partition length");
         }
 
-        var vp8FrameHeader = new Vp8FrameHeader()
+        Vp8FrameHeader vp8FrameHeader = new()
         {
             KeyFrame = true,
             Profile = (sbyte)version,
             PartitionLength = partitionLength
         };
 
-        var bitReader = new Vp8BitReader(
+        Vp8BitReader bitReader = new(
             stream,
             remaining,
             memoryAllocator,
@@ -121,7 +120,7 @@ internal static class WebpChunkParsingUtils
             Remaining = remaining
         };
 
-        return new WebpImageInfo()
+        return new()
         {
             Width = width,
             Height = height,
@@ -145,7 +144,7 @@ internal static class WebpChunkParsingUtils
         // VP8 data size.
         uint imageDataSize = ReadChunkSize(stream, buffer);
 
-        var bitReader = new Vp8LBitReader(stream, imageDataSize, memoryAllocator);
+        Vp8LBitReader bitReader = new(stream, imageDataSize, memoryAllocator);
 
         // One byte signature, should be 0x2f.
         uint signature = bitReader.ReadValue(8);
@@ -174,7 +173,7 @@ internal static class WebpChunkParsingUtils
             WebpThrowHelper.ThrowNotSupportedException($"Unexpected version number {version} found in VP8L header");
         }
 
-        return new WebpImageInfo()
+        return new()
         {
             Width = width,
             Height = height,
@@ -231,13 +230,13 @@ internal static class WebpChunkParsingUtils
         }
 
         // 3 bytes for the width.
-        uint width = ReadUnsignedInt24Bit(stream, buffer) + 1;
+        uint width = ReadUInt24LittleEndian(stream, buffer) + 1;
 
         // 3 bytes for the height.
-        uint height = ReadUnsignedInt24Bit(stream, buffer) + 1;
+        uint height = ReadUInt24LittleEndian(stream, buffer) + 1;
 
         // Read all the chunks in the order they occur.
-        var info = new WebpImageInfo()
+        WebpImageInfo info = new()
         {
             Width = width,
             Height = height,
@@ -253,7 +252,7 @@ internal static class WebpChunkParsingUtils
     /// <param name="stream">The stream to read from.</param>
     /// <param name="buffer">The buffer to store the read data into.</param>
     /// <returns>A unsigned 24 bit integer.</returns>
-    public static uint ReadUnsignedInt24Bit(BufferedReadStream stream, Span<byte> buffer)
+    public static uint ReadUInt24LittleEndian(BufferedReadStream stream, Span<byte> buffer)
     {
         if (stream.Read(buffer, 0, 3) == 3)
         {
@@ -261,7 +260,28 @@ internal static class WebpChunkParsingUtils
             return BinaryPrimitives.ReadUInt32LittleEndian(buffer);
         }
 
-        throw new ImageFormatException("Invalid Webp data, could not read unsigned integer.");
+        throw new ImageFormatException("Invalid Webp data, could not read unsigned 24 bit integer.");
+    }
+
+    /// <summary>
+    /// Writes a unsigned 24 bit integer.
+    /// </summary>
+    /// <param name="stream">The stream to read from.</param>
+    /// <param name="data">The uint24 data to write.</param>
+    public static unsafe void WriteUInt24LittleEndian(Stream stream, uint data)
+    {
+        if (data >= 1 << 24)
+        {
+            throw new InvalidDataException($"Invalid data, {data} is not a unsigned 24 bit integer.");
+        }
+
+        uint* ptr = &data;
+        byte* b = (byte*)ptr;
+
+        // Write the data in little endian.
+        stream.WriteByte(b[0]);
+        stream.WriteByte(b[1]);
+        stream.WriteByte(b[2]);
     }
 
     /// <summary>
@@ -298,7 +318,7 @@ internal static class WebpChunkParsingUtils
 
         if (stream.Read(buffer) == 4)
         {
-            var chunkType = (WebpChunkType)BinaryPrimitives.ReadUInt32BigEndian(buffer);
+            WebpChunkType chunkType = (WebpChunkType)BinaryPrimitives.ReadUInt32BigEndian(buffer);
             return chunkType;
         }
 
@@ -335,7 +355,7 @@ internal static class WebpChunkParsingUtils
 
                     if (metadata.ExifProfile != null)
                     {
-                        metadata.ExifProfile = new ExifProfile(exifData);
+                        metadata.ExifProfile = new(exifData);
                     }
 
                     break;
@@ -349,7 +369,7 @@ internal static class WebpChunkParsingUtils
 
                     if (metadata.XmpProfile != null)
                     {
-                        metadata.XmpProfile = new XmpProfile(xmpData);
+                        metadata.XmpProfile = new(xmpData);
                     }
 
                     break;

src/ImageSharp/Formats/Webp/WebpChunkType.cs

@@ -12,45 +12,54 @@ internal enum WebpChunkType : uint
     /// <summary>
     /// Header signaling the use of the VP8 format.
     /// </summary>
+    /// <remarks>VP8 (Single)</remarks>
     Vp8 = 0x56503820U,
 
     /// <summary>
     /// Header signaling the image uses lossless encoding.
     /// </summary>
+    /// <remarks>VP8L (Single)</remarks>
     Vp8L = 0x5650384CU,
 
     /// <summary>
     /// Header for a extended-VP8 chunk.
     /// </summary>
+    /// <remarks>VP8X (Single)</remarks>
     Vp8X = 0x56503858U,
 
     /// <summary>
     /// Chunk contains information about the alpha channel.
     /// </summary>
+    /// <remarks>ALPH (Single)</remarks>
     Alpha = 0x414C5048U,
 
     /// <summary>
     /// Chunk which contains a color profile.
     /// </summary>
+    /// <remarks>ICCP (Single)</remarks>
     Iccp = 0x49434350U,
 
     /// <summary>
     /// Chunk which contains EXIF metadata about the image.
     /// </summary>
+    /// <remarks>EXIF (Single)</remarks>
     Exif = 0x45584946U,
 
     /// <summary>
     /// Chunk contains XMP metadata about the image.
     /// </summary>
+    /// <remarks>XMP (Single)</remarks>
     Xmp = 0x584D5020U,
 
     /// <summary>
     /// For an animated image, this chunk contains the global parameters of the animation.
     /// </summary>
+    /// <remarks>ANIM (Single)</remarks>
     AnimationParameter = 0x414E494D,
 
     /// <summary>
     /// For animated images, this chunk contains information about a single frame. If the Animation flag is not set, then this chunk SHOULD NOT be present.
     /// </summary>
+    /// <remarks>ANMF (Multiple)</remarks>
     Animation = 0x414E4D46,
 }

src/ImageSharp/Formats/Webp/WebpConstants.cs

@@ -33,39 +33,6 @@ internal static class WebpConstants
     /// </summary>
     public const byte Vp8LHeaderMagicByte = 0x2F;
 
-    /// <summary>
-    /// Signature bytes identifying a lossy image.
-    /// </summary>
-    public static readonly byte[] Vp8MagicBytes =
-    {
-        0x56, // V
-        0x50, // P
-        0x38, // 8
-        0x20 // ' '
-    };
-
-    /// <summary>
-    /// Signature bytes identifying a lossless image.
-    /// </summary>
-    public static readonly byte[] Vp8LMagicBytes =
-    {
-        0x56, // V
-        0x50, // P
-        0x38, // 8
-        0x4C // L
-    };
-
-    /// <summary>
-    /// Signature bytes identifying a VP8X header.
-    /// </summary>
-    public static readonly byte[] Vp8XMagicBytes =
-    {
-        0x56, // V
-        0x50, // P
-        0x38, // 8
-        0x58 // X
-    };
-
     /// <summary>
     /// The header bytes identifying RIFF file.
     /// </summary>

src/ImageSharp/Formats/Webp/WebpDecoderCore.cs

@@ -93,11 +93,6 @@ internal sealed class WebpDecoderCore : IImageDecoderInternals, IDisposable
                     return animationDecoder.Decode<TPixel>(stream, this.webImageInfo.Features, this.webImageInfo.Width, this.webImageInfo.Height, fileSize);
                 }
 
-                if (this.webImageInfo.Features is { Animation: true })
-                {
-                    WebpThrowHelper.ThrowNotSupportedException("Animations are not supported");
-                }
-
                 image = new Image<TPixel>(this.configuration, (int)this.webImageInfo.Width, (int)this.webImageInfo.Height, metadata);
                 Buffer2D<TPixel> pixels = image.GetRootFramePixelBuffer();
                 if (this.webImageInfo.IsLossless)

tests/ImageSharp.Tests/Formats/WebP/YuvConversionTests.cs

@@ -143,7 +143,7 @@ public class YuvConversionTests
         };
 
         // act
-        YuvConversion.ConvertRgbToYuv(image, config, memoryAllocator, y, u, v);
+        YuvConversion.ConvertRgbToYuv(image.Frames.RootFrame, config, memoryAllocator, y, u, v);
 
         // assert
         Assert.True(expectedY.AsSpan().SequenceEqual(y));
@@ -249,7 +249,7 @@ public class YuvConversionTests
         };
 
         // act
-        YuvConversion.ConvertRgbToYuv(image, config, memoryAllocator, y, u, v);
+        YuvConversion.ConvertRgbToYuv(image.Frames.RootFrame, config, memoryAllocator, y, u, v);
 
         // assert
         Assert.True(expectedY.AsSpan().SequenceEqual(y));