Preparation

Author: Poker-sang

src/ImageSharp/Formats/Webp/AlphaEncoder.cs

@@ -19,25 +19,25 @@ 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>
     /// <param name="compress">Indicates, if the data should be compressed with the lossless webp compression.</param>
     /// <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,
         bool compress,
         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 @@ public static IMemoryOwner<byte> EncodeAlpha<TPixel>(
             // 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 @@ public static IMemoryOwner<byte> EncodeAlpha<TPixel>(
     /// 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 @@ protected void WriteRiffHeader(Stream stream, uint riffSize)
     {
         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 @@ protected void WriteMetadataProfile(Stream stream, byte[]? metadataBytes, WebpCh
         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 @@ protected void WriteMetadataProfile(Stream stream, byte[]? metadataBytes, WebpCh
         }
     }
 
+    /// <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 @@ protected void WriteMetadataProfile(Stream stream, byte[]? metadataBytes, WebpCh
     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 @@ protected void WriteAlphaChunk(Stream stream, Span<byte> dataBytes, bool alphaDa
         byte flags = 0;
         if (alphaDataIsCompressed)
         {
-            flags |= 1;
+            flags = 1;
         }
 
         stream.WriteByte(flags);
@@ -174,30 +230,6 @@ protected void WriteAlphaChunk(Stream stream, Span<byte> dataBytes, bool alphaDa
         }
     }
 
-    /// <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 @@ protected void WriteVp8XHeader(Stream stream, ExifProfile? exifProfile, XmpProfi
             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 @@ private void WriteWebpHeaders(
 
     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 @@ public Vp8LBitWriter Clone()
     {
         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 @@ public void WriteEncodedImageToStream(Stream stream, ExifProfile? exifProfile, X
         }
 
         // 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 @@ private void PutBitsFlushBits()
 
         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;