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Deduper works
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‎src/ImageSharp/Formats/AnimationUtilities.cs‎

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// Copyright (c) Six Labors.
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// Licensed under the Six Labors Split License.
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using System.Buffers;
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using System.Numerics;
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using System.Runtime.CompilerServices;
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using System.Runtime.InteropServices;
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using System.Runtime.Intrinsics;
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using System.Runtime.Intrinsics.X86;
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using SixLabors.ImageSharp.Advanced;
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using SixLabors.ImageSharp.Memory;
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using SixLabors.ImageSharp.PixelFormats;
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namespace SixLabors.ImageSharp.Formats;
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/// <summary>
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/// Utility methods for animated formats.
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/// </summary>
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internal static class AnimationUtilities
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{
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/// <summary>
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/// Deduplicates pixels between the previous and current frame returning only the changed pixels and bounds.
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/// </summary>
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/// <typeparam name="TPixel">The type of pixel format.</typeparam>
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/// <param name="configuration">The configuration.</param>
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/// <param name="previousFrame">The previous frame if present.</param>
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/// <param name="currentFrame">The current frame.</param>
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/// <param name="resultFrame">The resultant output.</param>
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/// <param name="replacement">The value to use when replacing duplicate pixels.</param>
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/// <returns>The <see cref="ValueTuple{Boolean, Rectangle}"/> representing the operation result.</returns>
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public static (bool Difference, Rectangle Bounds) DeDuplicatePixels<TPixel>(
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Configuration configuration,
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ImageFrame<TPixel>? previousFrame,
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ImageFrame<TPixel> currentFrame,
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ImageFrame<TPixel> resultFrame,
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Vector4 replacement)
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where TPixel : unmanaged, IPixel<TPixel>
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{
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MemoryAllocator memoryAllocator = configuration.MemoryAllocator;
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IMemoryOwner<Vector4> buffers = memoryAllocator.Allocate<Vector4>(currentFrame.Width * 3, AllocationOptions.Clean);
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Span<Vector4> previous = buffers.GetSpan()[..currentFrame.Width];
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Span<Vector4> current = buffers.GetSpan().Slice(currentFrame.Width, currentFrame.Width);
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Span<Vector4> result = buffers.GetSpan()[(currentFrame.Width * 2)..];
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int top = int.MinValue;
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int bottom = int.MaxValue;
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int left = int.MaxValue;
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int right = int.MinValue;
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bool hasDiff = false;
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for (int y = 0; y < currentFrame.Height; y++)
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{
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if (previousFrame != null)
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{
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PixelOperations<TPixel>.Instance.ToVector4(configuration, previousFrame.DangerousGetPixelRowMemory(y).Span, previous, PixelConversionModifiers.Scale);
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}
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PixelOperations<TPixel>.Instance.ToVector4(configuration, currentFrame.DangerousGetPixelRowMemory(y).Span, current, PixelConversionModifiers.Scale);
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ref Vector256<float> previousBase = ref Unsafe.As<Vector4, Vector256<float>>(ref MemoryMarshal.GetReference(previous));
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ref Vector256<float> currentBase = ref Unsafe.As<Vector4, Vector256<float>>(ref MemoryMarshal.GetReference(current));
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ref Vector256<float> resultBase = ref Unsafe.As<Vector4, Vector256<float>>(ref MemoryMarshal.GetReference(result));
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Vector256<float> replacement256 = Vector256.Create(replacement.X, replacement.Y, replacement.Z, replacement.W, replacement.X, replacement.Y, replacement.Z, replacement.W);
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int size = Unsafe.SizeOf<Vector4>();
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bool hasRowDiff = false;
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int i = 0;
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uint x = 0;
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int length = current.Length;
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int remaining = current.Length;
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if (Avx2.IsSupported && remaining >= 2)
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{
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while (remaining >= 2)
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{
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Vector256<float> p = Unsafe.Add(ref previousBase, x);
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Vector256<float> c = Unsafe.Add(ref currentBase, x);
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// Compare the previous and current pixels
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Vector256<float> neq = Avx.CompareEqual(p, c);
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Vector256<int> mask = neq.AsInt32();
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neq = Avx.Xor(neq, Vector256<float>.AllBitsSet);
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int m = Avx2.MoveMask(neq.AsByte());
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if (m != 0)
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{
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// If is diff is found, the left side is marked by the min of previously found left side and the diff position.
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// The right is the max of the previously found right side and the diff position + 1.
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int diff = (int)(i + (uint)(BitOperations.TrailingZeroCount(m) / size));
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left = Math.Min(left, diff);
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right = Math.Max(right, diff + 1);
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hasRowDiff = true;
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hasDiff = true;
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}
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// Capture the original alpha values.
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mask = Avx2.HorizontalAdd(mask, mask);
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mask = Avx2.HorizontalAdd(mask, mask);
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mask = Avx2.CompareEqual(mask, Vector256.Create(-4));
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Vector256<float> r = Avx.BlendVariable(c, replacement256, mask.AsSingle());
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Unsafe.Add(ref resultBase, x) = r;
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x++;
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i += 2;
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remaining -= 2;
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}
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}
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for (i = remaining; i > 0; i--)
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{
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x = (uint)(length - i);
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Vector4 p = Unsafe.Add(ref Unsafe.As<Vector256<float>, Vector4>(ref previousBase), x);
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Vector4 c = Unsafe.Add(ref Unsafe.As<Vector256<float>, Vector4>(ref currentBase), x);
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ref Vector4 r = ref Unsafe.Add(ref Unsafe.As<Vector256<float>, Vector4>(ref resultBase), x);
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if (p != c)
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{
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r = c;
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// If is diff is found, the left side is marked by the min of previously found left side and the diff position.
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// The right is the max of the previously found right side and the diff position + 1.
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left = Math.Min(left, (int)x);
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right = Math.Max(right, (int)x + 1);
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hasRowDiff = true;
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hasDiff = true;
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}
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else
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{
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r = replacement;
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}
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}
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if (hasRowDiff)
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{
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if (top == int.MinValue)
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{
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top = y;
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}
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bottom = y + 1;
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}
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PixelOperations<TPixel>.Instance.FromVector4Destructive(configuration, result, resultFrame.DangerousGetPixelRowMemory(y).Span, PixelConversionModifiers.Scale);
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}
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Rectangle bounds = Rectangle.FromLTRB(
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left = Numerics.Clamp(left, 0, resultFrame.Width - 1),
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top = Numerics.Clamp(top, 0, resultFrame.Height - 1),
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Numerics.Clamp(right, left + 1, resultFrame.Width),
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Numerics.Clamp(bottom, top + 1, resultFrame.Height));
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return new(hasDiff, bounds);
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}
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}

‎src/ImageSharp/Formats/Gif/GifEncoder.cs‎

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// Copyright (c) Six Labors.
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// Licensed under the Six Labors Split License.
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using SixLabors.ImageSharp.Advanced;
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namespace SixLabors.ImageSharp.Formats.Gif;
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/// <summary>

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