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@ -1,4 +1,4 @@ |
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// Copyright (c) Six Labors and contributors.
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// Copyright (c) Six Labors and contributors.
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// Licensed under the Apache License, Version 2.0.
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// Licensed under the Apache License, Version 2.0.
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using System; |
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using System; |
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@ -41,13 +41,33 @@ namespace SixLabors.ImageSharp.Formats.Gif |
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/// </summary>
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/// </summary>
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private const int HashSize = 5003; |
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private const int HashSize = 5003; |
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/// <summary>
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/// The amount to shift each code.
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/// </summary>
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private const int HashShift = 4; |
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/// <summary>
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/// <summary>
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/// Mask used when shifting pixel values
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/// Mask used when shifting pixel values
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/// </summary>
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/// </summary>
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private static readonly int[] Masks = |
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private static readonly int[] Masks = |
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{ |
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{ |
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0x0000, 0x0001, 0x0003, 0x0007, 0x000F, 0x001F, 0x003F, 0x007F, 0x00FF, |
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0b0, |
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0x01FF, 0x03FF, 0x07FF, 0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF |
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0b1, |
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0b11, |
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0b111, |
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0b1111, |
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0b11111, |
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0b111111, |
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0b1111111, |
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0b11111111, |
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0b111111111, |
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0b1111111111, |
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0b11111111111, |
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0b111111111111, |
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0b1111111111111, |
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0b11111111111111, |
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0b111111111111111, |
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0b1111111111111111 |
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}; |
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}; |
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/// <summary>
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/// <summary>
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@ -80,16 +100,6 @@ namespace SixLabors.ImageSharp.Formats.Gif |
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/// </summary>
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/// </summary>
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private readonly byte[] accumulators = new byte[256]; |
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private readonly byte[] accumulators = new byte[256]; |
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/// <summary>
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/// For dynamic table sizing
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/// </summary>
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private readonly int hsize = HashSize; |
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/// <summary>
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/// The current position within the pixelArray.
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/// </summary>
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private int position; |
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/// <summary>
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/// <summary>
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/// Number of bits/code
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/// Number of bits/code
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/// </summary>
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/// </summary>
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@ -177,15 +187,13 @@ namespace SixLabors.ImageSharp.Formats.Gif |
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/// <summary>
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/// <summary>
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/// Encodes and compresses the indexed pixels to the stream.
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/// Encodes and compresses the indexed pixels to the stream.
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/// </summary>
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/// </summary>
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/// <param name="indexedPixels">The span of indexed pixels.</param>
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/// <param name="indexedPixels">The 2D buffer of indexed pixels.</param>
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/// <param name="stream">The stream to write to.</param>
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/// <param name="stream">The stream to write to.</param>
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public void Encode(ReadOnlySpan<byte> indexedPixels, Stream stream) |
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public void Encode(Buffer2D<byte> indexedPixels, Stream stream) |
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{ |
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{ |
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// Write "initial code size" byte
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// Write "initial code size" byte
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stream.WriteByte((byte)this.initialCodeSize); |
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stream.WriteByte((byte)this.initialCodeSize); |
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this.position = 0; |
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// Compress and write the pixel data
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// Compress and write the pixel data
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this.Compress(indexedPixels, this.initialCodeSize + 1, stream); |
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this.Compress(indexedPixels, this.initialCodeSize + 1, stream); |
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@ -199,10 +207,7 @@ namespace SixLabors.ImageSharp.Formats.Gif |
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/// <param name="bitCount">The number of bits</param>
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/// <param name="bitCount">The number of bits</param>
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/// <returns>See <see cref="int"/></returns>
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/// <returns>See <see cref="int"/></returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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private static int GetMaxcode(int bitCount) |
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private static int GetMaxcode(int bitCount) => (1 << bitCount) - 1; |
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{ |
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return (1 << bitCount) - 1; |
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} |
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/// <summary>
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/// <summary>
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/// Add a character to the end of the current packet, and if it is 254 characters,
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/// Add a character to the end of the current packet, and if it is 254 characters,
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@ -239,25 +244,16 @@ namespace SixLabors.ImageSharp.Formats.Gif |
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/// Reset the code table.
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/// Reset the code table.
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/// </summary>
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/// </summary>
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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private void ResetCodeTable() |
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private void ResetCodeTable() => this.hashTable.GetSpan().Fill(-1); |
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{ |
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this.hashTable.GetSpan().Fill(-1); |
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} |
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/// <summary>
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/// <summary>
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/// Compress the packets to the stream.
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/// Compress the packets to the stream.
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/// </summary>
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/// </summary>
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/// <param name="indexedPixels">The span of indexed pixels.</param>
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/// <param name="indexedPixels">The 2D buffer of indexed pixels.</param>
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/// <param name="initialBits">The initial bits.</param>
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/// <param name="initialBits">The initial bits.</param>
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/// <param name="stream">The stream to write to.</param>
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/// <param name="stream">The stream to write to.</param>
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private void Compress(ReadOnlySpan<byte> indexedPixels, int initialBits, Stream stream) |
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private void Compress(Buffer2D<byte> indexedPixels, int initialBits, Stream stream) |
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{ |
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{ |
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int fcode; |
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int c; |
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int ent; |
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int hsizeReg; |
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int hshift; |
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// Set up the globals: globalInitialBits - initial number of bits
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// Set up the globals: globalInitialBits - initial number of bits
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this.globalInitialBits = initialBits; |
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this.globalInitialBits = initialBits; |
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@ -265,92 +261,82 @@ namespace SixLabors.ImageSharp.Formats.Gif |
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this.clearFlag = false; |
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this.clearFlag = false; |
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this.bitCount = this.globalInitialBits; |
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this.bitCount = this.globalInitialBits; |
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this.maxCode = GetMaxcode(this.bitCount); |
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this.maxCode = GetMaxcode(this.bitCount); |
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this.clearCode = 1 << (initialBits - 1); |
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this.clearCode = 1 << (initialBits - 1); |
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this.eofCode = this.clearCode + 1; |
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this.eofCode = this.clearCode + 1; |
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this.freeEntry = this.clearCode + 2; |
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this.freeEntry = this.clearCode + 2; |
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this.accumulatorCount = 0; // Clear packet
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this.accumulatorCount = 0; // clear packet
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this.ResetCodeTable(); // Clear hash table
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ent = this.NextPixel(indexedPixels); |
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// TODO: PERF: It looks like hshift could be calculated once statically.
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hshift = 0; |
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for (fcode = this.hsize; fcode < 65536; fcode *= 2) |
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{ |
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++hshift; |
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} |
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hshift = 8 - hshift; // set hash code range bound
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hsizeReg = this.hsize; |
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this.ResetCodeTable(); // clear hash table
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this.Output(this.clearCode, stream); |
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this.Output(this.clearCode, stream); |
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ref int hashTableRef = ref MemoryMarshal.GetReference(this.hashTable.GetSpan()); |
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ref int hashTableRef = ref MemoryMarshal.GetReference(this.hashTable.GetSpan()); |
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ref int codeTableRef = ref MemoryMarshal.GetReference(this.codeTable.GetSpan()); |
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ref int codeTableRef = ref MemoryMarshal.GetReference(this.codeTable.GetSpan()); |
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while (this.position < indexedPixels.Length) |
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int entry = indexedPixels[0, 0]; |
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{ |
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c = this.NextPixel(indexedPixels); |
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fcode = (c << MaxBits) + ent; |
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for (int y = 0; y < indexedPixels.Height; y++) |
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int i = (c << hshift) ^ ent /* = 0 */; |
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{ |
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ref byte rowSpanRef = ref MemoryMarshal.GetReference(indexedPixels.GetRowSpan(y)); |
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int offsetX = y == 0 ? 1 : 0; |
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if (Unsafe.Add(ref hashTableRef, i) == fcode) |
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for (int x = offsetX; x < indexedPixels.Width; x++) |
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{ |
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{ |
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ent = Unsafe.Add(ref codeTableRef, i); |
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int code = Unsafe.Add(ref rowSpanRef, x); |
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continue; |
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int freeCode = (code << MaxBits) + entry; |
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} |
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int hashIndex = (code << HashShift) ^ entry; |
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// Non-empty slot
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if (Unsafe.Add(ref hashTableRef, hashIndex) == freeCode) |
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if (Unsafe.Add(ref hashTableRef, i) >= 0) |
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{ |
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int disp = 1; |
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if (i != 0) |
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{ |
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{ |
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disp = hsizeReg - i; |
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entry = Unsafe.Add(ref codeTableRef, hashIndex); |
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continue; |
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} |
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} |
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do |
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// Non-empty slot
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if (Unsafe.Add(ref hashTableRef, hashIndex) >= 0) |
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{ |
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{ |
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if ((i -= disp) < 0) |
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int disp = 1; |
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if (hashIndex != 0) |
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{ |
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disp = HashSize - hashIndex; |
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} |
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do |
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{ |
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{ |
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i += hsizeReg; |
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if ((hashIndex -= disp) < 0) |
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{ |
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hashIndex += HashSize; |
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} |
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if (Unsafe.Add(ref hashTableRef, hashIndex) == freeCode) |
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{ |
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entry = Unsafe.Add(ref codeTableRef, hashIndex); |
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break; |
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} |
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} |
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} |
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while (Unsafe.Add(ref hashTableRef, hashIndex) >= 0); |
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if (Unsafe.Add(ref hashTableRef, i) == fcode) |
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if (Unsafe.Add(ref hashTableRef, hashIndex) == freeCode) |
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{ |
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{ |
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ent = Unsafe.Add(ref codeTableRef, i); |
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continue; |
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break; |
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} |
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} |
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} |
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} |
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while (Unsafe.Add(ref hashTableRef, i) >= 0); |
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if (Unsafe.Add(ref hashTableRef, i) == fcode) |
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this.Output(entry, stream); |
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entry = code; |
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if (this.freeEntry < MaxMaxCode) |
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{ |
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{ |
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continue; |
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Unsafe.Add(ref codeTableRef, hashIndex) = this.freeEntry++; // code -> hashtable
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Unsafe.Add(ref hashTableRef, hashIndex) = freeCode; |
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} |
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else |
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{ |
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this.ClearBlock(stream); |
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} |
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} |
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} |
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this.Output(ent, stream); |
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ent = c; |
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if (this.freeEntry < MaxMaxCode) |
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{ |
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Unsafe.Add(ref codeTableRef, i) = this.freeEntry++; // code -> hashtable
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Unsafe.Add(ref hashTableRef, i) = fcode; |
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} |
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else |
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{ |
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this.ClearBlock(stream); |
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} |
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} |
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} |
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} |
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// Put out the final code.
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// Output the final code.
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this.Output(ent, stream); |
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this.Output(entry, stream); |
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this.Output(this.eofCode, stream); |
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this.Output(this.eofCode, stream); |
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} |
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} |
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@ -366,19 +352,6 @@ namespace SixLabors.ImageSharp.Formats.Gif |
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this.accumulatorCount = 0; |
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this.accumulatorCount = 0; |
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} |
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} |
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/// <summary>
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/// Reads the next pixel from the image.
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/// </summary>
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/// <param name="indexedPixels">The span of indexed pixels.</param>
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/// <returns>
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/// The <see cref="int"/>
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/// </returns>
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[MethodImpl(MethodImplOptions.AggressiveInlining)] |
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private int NextPixel(ReadOnlySpan<byte> indexedPixels) |
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{ |
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return indexedPixels[this.position++] & 0xFF; |
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} |
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/// <summary>
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/// <summary>
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/// Output the current code to the stream.
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/// Output the current code to the stream.
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/// </summary>
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/// </summary>
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Brian Popow
6 years ago
GitHub