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Merge pull request #2455 from SixLabors/js/gif-fixes
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Preserve Gif color palettes and deduplicate frame pixels.
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@JimBobSquarePants
JimBobSquarePants committed Sep 18, 2023
2 parents da4d4d7 + 9ddebdd commit 945a83f
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Showing 70 changed files with 1,108 additions and 326 deletions.
4 changes: 2 additions & 2 deletions src/ImageSharp/Color/Color.Conversions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -139,7 +139,7 @@ public Color(Vector4 vector)
/// </summary>
/// <param name="color">The <see cref="Color"/>.</param>
/// <returns>The <see cref="Vector4"/>.</returns>
public static explicit operator Vector4(Color color) => color.ToVector4();
public static explicit operator Vector4(Color color) => color.ToScaledVector4();

/// <summary>
/// Converts an <see cref="Vector4"/> to <see cref="Color"/>.
Expand Down Expand Up @@ -228,7 +228,7 @@ internal Bgr24 ToBgr24()
}

[MethodImpl(InliningOptions.ShortMethod)]
internal Vector4 ToVector4()
internal Vector4 ToScaledVector4()
{
if (this.boxedHighPrecisionPixel is null)
{
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27 changes: 27 additions & 0 deletions src/ImageSharp/Common/Helpers/SimdUtils.HwIntrinsics.cs
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Expand Up @@ -629,6 +629,33 @@ public static Vector256<float> MultiplyAddNegated(
return Avx.Subtract(c, Avx.Multiply(a, b));
}

/// <summary>
/// Blend packed 8-bit integers from <paramref name="left"/> and <paramref name="right"/> using <paramref name="mask"/>.
/// The high bit of each corresponding <paramref name="mask"/> byte determines the selection.
/// If the high bit is set the element of <paramref name="left"/> is selected.
/// The element of <paramref name="right"/> is selected otherwise.
/// </summary>
/// <param name="left">The left vector.</param>
/// <param name="right">The right vector.</param>
/// <param name="mask">The mask vector.</param>
/// <returns>The <see cref="Vector256{T}"/>.</returns>
[MethodImpl(MethodImplOptions.AggressiveInlining)]
public static Vector128<byte> BlendVariable(Vector128<byte> left, Vector128<byte> right, Vector128<byte> mask)
{
if (Sse41.IsSupported)
{
return Sse41.BlendVariable(left, right, mask);
}
else if (Sse2.IsSupported)
{
return Sse2.Or(Sse2.And(right, mask), Sse2.AndNot(mask, left));
}

// Use a signed shift right to create a mask with the sign bit.
Vector128<short> signedMask = AdvSimd.ShiftRightArithmetic(mask.AsInt16(), 7);
return AdvSimd.BitwiseSelect(signedMask, right.AsInt16(), left.AsInt16()).AsByte();
}

/// <summary>
/// <see cref="ByteToNormalizedFloat"/> as many elements as possible, slicing them down (keeping the remainder).
/// </summary>
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6 changes: 6 additions & 0 deletions src/ImageSharp/Formats/Bmp/BmpEncoder.cs
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Expand Up @@ -2,6 +2,7 @@
// Licensed under the Six Labors Split License.

using SixLabors.ImageSharp.Advanced;
using SixLabors.ImageSharp.Processing;

namespace SixLabors.ImageSharp.Formats.Bmp;

Expand All @@ -10,6 +11,11 @@ namespace SixLabors.ImageSharp.Formats.Bmp;
/// </summary>
public sealed class BmpEncoder : QuantizingImageEncoder
{
/// <summary>
/// Initializes a new instance of the <see cref="BmpEncoder"/> class.
/// </summary>
public BmpEncoder() => this.Quantizer = KnownQuantizers.Octree;

/// <summary>
/// Gets the number of bits per pixel.
/// </summary>
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3 changes: 2 additions & 1 deletion src/ImageSharp/Formats/Bmp/BmpEncoderCore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.Metadata;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;
using SixLabors.ImageSharp.Processing.Processors.Quantization;

namespace SixLabors.ImageSharp.Formats.Bmp;
Expand Down Expand Up @@ -100,7 +101,7 @@ public BmpEncoderCore(BmpEncoder encoder, MemoryAllocator memoryAllocator)
{
this.memoryAllocator = memoryAllocator;
this.bitsPerPixel = encoder.BitsPerPixel;
this.quantizer = encoder.Quantizer;
this.quantizer = encoder.Quantizer ?? KnownQuantizers.Octree;
this.pixelSamplingStrategy = encoder.PixelSamplingStrategy;
this.infoHeaderType = encoder.SupportTransparency ? BmpInfoHeaderType.WinVersion4 : BmpInfoHeaderType.WinVersion3;
}
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70 changes: 53 additions & 17 deletions src/ImageSharp/Formats/Gif/GifDecoderCore.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,16 @@ internal sealed class GifDecoderCore : IImageDecoderInternals
/// </summary>
private IMemoryOwner<byte>? globalColorTable;

/// <summary>
/// The current local color table.
/// </summary>
private IMemoryOwner<byte>? currentLocalColorTable;

/// <summary>
/// Gets the size in bytes of the current local color table.
/// </summary>
private int currentLocalColorTableSize;

/// <summary>
/// The area to restore.
/// </summary>
Expand Down Expand Up @@ -159,6 +169,7 @@ public Image<TPixel> Decode<TPixel>(BufferedReadStream stream, CancellationToken
finally
{
this.globalColorTable?.Dispose();
this.currentLocalColorTable?.Dispose();
}

if (image is null)
Expand Down Expand Up @@ -229,6 +240,7 @@ public ImageInfo Identify(BufferedReadStream stream, CancellationToken cancellat
finally
{
this.globalColorTable?.Dispose();
this.currentLocalColorTable?.Dispose();
}

if (this.logicalScreenDescriptor.Width == 0 && this.logicalScreenDescriptor.Height == 0)
Expand Down Expand Up @@ -332,7 +344,7 @@ private void ReadApplicationExtension(BufferedReadStream stream)
if (subBlockSize == GifConstants.NetscapeLoopingSubBlockSize)
{
stream.Read(this.buffer.Span, 0, GifConstants.NetscapeLoopingSubBlockSize);
this.gifMetadata!.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.Span.Slice(1)).RepeatCount;
this.gifMetadata!.RepeatCount = GifNetscapeLoopingApplicationExtension.Parse(this.buffer.Span[1..]).RepeatCount;
stream.Skip(1); // Skip the terminator.
return;
}
Expand Down Expand Up @@ -415,25 +427,27 @@ private void ReadFrame<TPixel>(BufferedReadStream stream, ref Image<TPixel>? ima
{
this.ReadImageDescriptor(stream);

IMemoryOwner<byte>? localColorTable = null;
Buffer2D<byte>? indices = null;
try
{
// Determine the color table for this frame. If there is a local one, use it otherwise use the global color table.
if (this.imageDescriptor.LocalColorTableFlag)
bool hasLocalColorTable = this.imageDescriptor.LocalColorTableFlag;

if (hasLocalColorTable)
{
int length = this.imageDescriptor.LocalColorTableSize * 3;
localColorTable = this.configuration.MemoryAllocator.Allocate<byte>(length, AllocationOptions.Clean);
stream.Read(localColorTable.GetSpan());
// Read and store the local color table. We allocate the maximum possible size and slice to match.
int length = this.currentLocalColorTableSize = this.imageDescriptor.LocalColorTableSize * 3;
this.currentLocalColorTable ??= this.configuration.MemoryAllocator.Allocate<byte>(768, AllocationOptions.Clean);
stream.Read(this.currentLocalColorTable.GetSpan()[..length]);
}

indices = this.configuration.MemoryAllocator.Allocate2D<byte>(this.imageDescriptor.Width, this.imageDescriptor.Height, AllocationOptions.Clean);
this.ReadFrameIndices(stream, indices);

Span<byte> rawColorTable = default;
if (localColorTable != null)
if (hasLocalColorTable)
{
rawColorTable = localColorTable.GetSpan();
rawColorTable = this.currentLocalColorTable!.GetSpan()[..this.currentLocalColorTableSize];
}
else if (this.globalColorTable != null)
{
Expand All @@ -448,7 +462,6 @@ private void ReadFrame<TPixel>(BufferedReadStream stream, ref Image<TPixel>? ima
}
finally
{
localColorTable?.Dispose();
indices?.Dispose();
}
}
Expand Down Expand Up @@ -509,7 +522,10 @@ private void ReadFrameColors<TPixel>(ref Image<TPixel>? image, ref ImageFrame<TP
prevFrame = previousFrame;
}

currentFrame = image!.Frames.CreateFrame();
// We create a clone of the frame and add it.
// We will overpaint the difference of pixels on the current frame to create a complete image.
// This ensures that we have enough pixel data to process without distortion. #2450
currentFrame = image!.Frames.AddFrame(previousFrame);

this.SetFrameMetadata(currentFrame.Metadata);

Expand Down Expand Up @@ -631,7 +647,10 @@ private void ReadFrameMetadata(BufferedReadStream stream, List<ImageFrameMetadat
// Skip the color table for this frame if local.
if (this.imageDescriptor.LocalColorTableFlag)
{
stream.Skip(this.imageDescriptor.LocalColorTableSize * 3);
// Read and store the local color table. We allocate the maximum possible size and slice to match.
int length = this.currentLocalColorTableSize = this.imageDescriptor.LocalColorTableSize * 3;
this.currentLocalColorTable ??= this.configuration.MemoryAllocator.Allocate<byte>(768, AllocationOptions.Clean);
stream.Read(this.currentLocalColorTable.GetSpan()[..length]);
}

// Skip the frame indices. Pixels length + mincode size.
Expand Down Expand Up @@ -682,21 +701,30 @@ private void SetFrameMetadata(ImageFrameMetadata metadata)
{
GifFrameMetadata gifMeta = metadata.GetGifMetadata();
gifMeta.ColorTableMode = GifColorTableMode.Global;
gifMeta.ColorTableLength = this.logicalScreenDescriptor.GlobalColorTableSize;
}

if (this.imageDescriptor.LocalColorTableFlag
&& this.imageDescriptor.LocalColorTableSize > 0)
{
GifFrameMetadata gifMeta = metadata.GetGifMetadata();
gifMeta.ColorTableMode = GifColorTableMode.Local;
gifMeta.ColorTableLength = this.imageDescriptor.LocalColorTableSize;

Color[] colorTable = new Color[this.imageDescriptor.LocalColorTableSize];
ReadOnlySpan<Rgb24> rgbTable = MemoryMarshal.Cast<byte, Rgb24>(this.currentLocalColorTable!.GetSpan()[..this.currentLocalColorTableSize]);
for (int i = 0; i < colorTable.Length; i++)
{
colorTable[i] = new Color(rgbTable[i]);
}

gifMeta.LocalColorTable = colorTable;
}

// Graphics control extensions is optional.
if (this.graphicsControlExtension != default)
{
GifFrameMetadata gifMeta = metadata.GetGifMetadata();
gifMeta.HasTransparency = this.graphicsControlExtension.TransparencyFlag;
gifMeta.TransparencyIndex = this.graphicsControlExtension.TransparencyIndex;
gifMeta.FrameDelay = this.graphicsControlExtension.DelayTime;
gifMeta.DisposalMethod = this.graphicsControlExtension.DisposalMethod;
}
Expand Down Expand Up @@ -751,14 +779,22 @@ private void ReadLogicalScreenDescriptorAndGlobalColorTable(BufferedReadStream s
if (this.logicalScreenDescriptor.GlobalColorTableFlag)
{
int globalColorTableLength = this.logicalScreenDescriptor.GlobalColorTableSize * 3;
this.gifMetadata.GlobalColorTableLength = globalColorTableLength;

if (globalColorTableLength > 0)
{
this.globalColorTable = this.memoryAllocator.Allocate<byte>(globalColorTableLength, AllocationOptions.Clean);

// Read the global color table data from the stream
stream.Read(this.globalColorTable.GetSpan());
// Read the global color table data from the stream and preserve it in the gif metadata
Span<byte> globalColorTableSpan = this.globalColorTable.GetSpan();
stream.Read(globalColorTableSpan);

Color[] colorTable = new Color[this.logicalScreenDescriptor.GlobalColorTableSize];
ReadOnlySpan<Rgb24> rgbTable = MemoryMarshal.Cast<byte, Rgb24>(globalColorTableSpan);
for (int i = 0; i < colorTable.Length; i++)
{
colorTable[i] = new Color(rgbTable[i]);
}

this.gifMetadata.GlobalColorTable = colorTable;
}
}
}
Expand Down
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