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Refactor lossless decoding to match better original implementation

pull/1147/head
Brian Popow 7 years ago
parent
486edbc33d
commit
23ee03faf7
2 changed files with 74 additions and 57 deletions
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  1. 26
      src/ImageSharp/Formats/WebP/HuffmanUtils.cs
  2. 105
      src/ImageSharp/Formats/WebP/WebPLosslessDecoder.cs

26
src/ImageSharp/Formats/WebP/HuffmanUtils.cs
View File

@ -23,16 +23,11 @@ namespace SixLabors.ImageSharp.Formats.WebP
// sorted[code_lengths_size] is a pre-allocated array for sorting symbols by code length.
var sorted = new int[codeLengthsSize];
// total size root table + 2nd level table
int totalSize = 1 << rootBits;
// current code length
int len;
// symbol index in original or sorted table
int symbol;
// number of codes of each length:
var count = new int[WebPConstants.MaxAllowedCodeLength + 1];
// offsets in sorted table for each length
var offset = new int[WebPConstants.MaxAllowedCodeLength + 1];
int totalSize = 1 << rootBits; // total size root table + 2nd level table
int len; // current code length
int symbol; // symbol index in original or sorted table
var count = new int[WebPConstants.MaxAllowedCodeLength + 1]; // number of codes of each length
var offset = new int[WebPConstants.MaxAllowedCodeLength + 1]; // offsets in sorted table for each length
// Build histogram of code lengths.
for (symbol = 0; symbol < codeLengthsSize; ++symbol)
@ -45,6 +40,12 @@ namespace SixLabors.ImageSharp.Formats.WebP
count[codeLengths[symbol]]++;
}
// Error, all code lengths are zeros.
if (count[0] == codeLengthsSize)
{
return 0;
}
// Generate offsets into sorted symbol table by code length.
offset[1] = 0;
for (len = 1; len < WebPConstants.MaxAllowedCodeLength; ++len)
@ -88,6 +89,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
int tableBits = rootBits; // key length of current table
int tableSize = 1 << tableBits; // size of current table
symbol = 0;
// Fill in root table.
for (len = 1, step = 2; len <= rootBits; ++len, step <<= 1)
{
@ -132,9 +134,9 @@ namespace SixLabors.ImageSharp.Formats.WebP
tableSize = 1 << tableBits;
totalSize += tableSize;
low = key & mask;
table[low].BitsUsed = tableBits + rootBits;
// TODO: fix this
//rootTable[low].bits = (tableBits + rootBits);
//rootTable[low].value = ((table - rootTable) - low);
// table[low].Value = ((table - rootTable) - low);
}
var huffmanCode = new HuffmanCode

105
src/ImageSharp/Formats/WebP/WebPLosslessDecoder.cs
View File

@ -4,7 +4,6 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using SixLabors.ImageSharp.Memory;
using SixLabors.ImageSharp.PixelFormats;
@ -48,8 +47,8 @@ namespace SixLabors.ImageSharp.Formats.WebP
FixedTableSize + 2704
};
public static int NumCodeLengthCodes = 19;
public static byte[] KCodeLengthCodeOrder = { 17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
private static readonly int NumCodeLengthCodes = 19;
private static readonly byte[] KCodeLengthCodeOrder = { 17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
private static readonly int CodeToPlaneCodes = 120;
private static readonly int[] KCodeToPlane =
@ -81,9 +80,35 @@ namespace SixLabors.ImageSharp.Formats.WebP
public void Decode<TPixel>(Buffer2D<TPixel> pixels, int width, int height)
where TPixel : struct, IPixel<TPixel>
{
uint[] pixelData = this.DecodeImageStream(width, height, true);
this.DecodePixelValues(width, height, pixelData, pixels);
}
private void DecodePixelValues<TPixel>(int width, int height, uint[] pixelData, Buffer2D<TPixel> pixels)
where TPixel : struct, IPixel<TPixel>
{
TPixel color = default;
for (int y = 0; y < height; y++)
{
Span<TPixel> pixelRow = pixels.GetRowSpan(y);
for (int x = 0; x < width; x++)
{
int idx = (y * width) + x;
uint pixel = pixelData[idx];
uint a = (pixel & 0xFF000000) >> 24;
uint r = (pixel & 0xFF0000) >> 16;
uint g = (pixel & 0xFF00) >> 8;
uint b = pixel & 0xFF;
color.FromRgba32(new Rgba32(r, g, b, a));
pixelRow[x] = color;
}
}
}
private uint[] DecodeImageStream(int xSize, int ySize, bool isLevel0)
{
this.ReadTransformations();
int xsize = 0, ysize = 0;
// Read color cache, if present.
bool colorCachePresent = this.bitReader.ReadBit();
@ -102,11 +127,17 @@ namespace SixLabors.ImageSharp.Formats.WebP
colorCache.Init(colorCacheBits);
}
Vp8LMetadata metadata = this.ReadHuffmanCodes(xsize, ysize, colorCacheBits);
Vp8LMetadata metadata = this.ReadHuffmanCodes(xSize, ySize, colorCacheBits, isLevel0);
var numBits = 0; // TODO: use huffmanSubsampleBits.
metadata.HuffmanMask = (numBits == 0) ? ~0 : (1 << numBits) - 1;
metadata.ColorCacheSize = colorCacheSize;
uint[] pixelData = this.DecodeImageData(xSize, ySize, colorCacheSize, metadata, colorCache);
return pixelData;
}
private uint[] DecodeImageData(int width, int height, int colorCacheSize, Vp8LMetadata metadata, ColorCache colorCache)
{
int lastPixel = 0;
int row = lastPixel / width;
int col = lastPixel % width;
@ -115,7 +146,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
bool decIsIncremental = false; // TODO: determine correct value for decIsIncremental
int nextSyncRow = decIsIncremental ? row : 1 << 24;
int mask = metadata.HuffmanMask;
HTreeGroup[] hTreeGroup = this.GetHtreeGroupForPos(metadata, col, row);
HTreeGroup[] hTreeGroup = this.GetHTreeGroupForPos(metadata, col, row);
var pixelData = new uint[width * height];
int totalPixels = width * height;
@ -126,7 +157,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
int code = 0;
if ((col & mask) == 0)
{
hTreeGroup = this.GetHtreeGroupForPos(metadata, col, row);
hTreeGroup = this.GetHTreeGroupForPos(metadata, col, row);
}
if (hTreeGroup[0].IsTrivialCode)
@ -180,8 +211,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
}
int pixelIdx = decodedPixels * 4;
pixelData[pixelIdx] =
(uint)(((byte)alpha << 24) | ((byte)red << 16) | ((byte)code << 8) | (byte)blue);
pixelData[pixelIdx] = (uint)(((byte)alpha << 24) | ((byte)red << 16) | ((byte)code << 8) | (byte)blue);
}
this.AdvanceByOne(ref col, ref row, width, colorCache, ref decodedPixels, pixelData, ref lastCached);
@ -211,7 +241,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
if ((col & mask) != 0)
{
hTreeGroup = this.GetHtreeGroupForPos(metadata, col, row);
hTreeGroup = this.GetHTreeGroupForPos(metadata, col, row);
}
if (colorCache != null)
@ -242,22 +272,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
}
}
TPixel color = default;
for (int y = 0; y < height; y++)
{
Span<TPixel> pixelRow = pixels.GetRowSpan(y);
for (int x = 0; x < width; x++)
{
int idx = (y * width) + x;
uint pixel = pixelData[idx];
uint a = (pixel & 0xFF000000) >> 24;
uint r = (pixel & 0xFF0000) >> 16;
uint g = (pixel & 0xFF00) >> 8;
uint b = pixel & 0xFF;
color.FromRgba32(new Rgba32(r, g, b, a));
pixelRow[x] = color;
}
}
return pixelData;
}
private void AdvanceByOne(ref int col, ref int row, int width, ColorCache colorCache, ref int decodedPixels, uint[] pixelData, ref int lastCached)
@ -284,27 +299,27 @@ namespace SixLabors.ImageSharp.Formats.WebP
}
}
private Vp8LMetadata ReadHuffmanCodes(int xSize, int ySize, int colorCacheBits, bool allowRecursion = true)
private Vp8LMetadata ReadHuffmanCodes(int xSize, int ySize, int colorCacheBits, bool allowRecursion)
{
int maxAlphabetSize = 0;
int numHtreeGroups = 1;
int numHtreeGroupsMax = 1;
int numHTreeGroups = 1;
int numHTreeGroupsMax = 1;
// Read the Huffman codes.
// If the next bit is zero, there is only one meta Huffman code used everywhere in the image. No more data is stored.
// If this bit is one, the image uses multiple meta Huffman codes. These meta Huffman codes are stored as an entropy image.
bool isEntropyImage = this.bitReader.ReadBit();
if (isEntropyImage)
if (allowRecursion && isEntropyImage)
{
// Use meta Huffman codes.
uint huffmanPrecision = this.bitReader.ReadBits(3) + 2;
int huffmanXSize = SubSampleSize(xSize, (int)huffmanPrecision);
int huffmanYSize = SubSampleSize(ySize, (int)huffmanPrecision);
int huffmanXSize = this.SubSampleSize(xSize, (int)huffmanPrecision);
int huffmanYSize = this.SubSampleSize(ySize, (int)huffmanPrecision);
int huffmanPixs = huffmanXSize * huffmanYSize;
// TODO: decode entropy image
return new Vp8LMetadata();
}
// Find maximum alphabet size for the htree group.
// Find maximum alphabet size for the hTree group.
for (int j = 0; j < WebPConstants.HuffmanCodesPerMetaCode; j++)
{
int alphabetSize = WebPConstants.kAlphabetSize[j];
@ -320,14 +335,13 @@ namespace SixLabors.ImageSharp.Formats.WebP
}
int tableSize = KTableSize[colorCacheBits];
var huffmanTables = new HuffmanCode[numHtreeGroups * tableSize];
var hTreeGroups = new HTreeGroup[numHtreeGroups];
var huffmanTables = new HuffmanCode[numHTreeGroups * tableSize];
var hTreeGroups = new HTreeGroup[numHTreeGroups];
Span<HuffmanCode> huffmanTable = huffmanTables.AsSpan();
for (int i = 0; i < numHtreeGroupsMax; i++)
for (int i = 0; i < numHTreeGroupsMax; i++)
{
hTreeGroups[i] = new HTreeGroup(HuffmanUtils.HuffmanPackedTableSize);
HTreeGroup hTreeGroup = hTreeGroups[i];
int size;
int totalSize = 0;
bool isTrivialLiteral = true;
int maxBits = 0;
@ -340,7 +354,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
alphabetSize += 1 << colorCacheBits;
}
size = this.ReadHuffmanCode(alphabetSize, codeLengths, huffmanTable);
int size = this.ReadHuffmanCode(alphabetSize, codeLengths, huffmanTable);
if (size is 0)
{
WebPThrowHelper.ThrowImageFormatException("Huffman table size is zero");
@ -356,7 +370,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
totalSize += huffmanTable[0].BitsUsed;
huffmanTable = huffmanTable.Slice(size);
if (j <= (int)HuffIndex.Alpha)
if (j <= HuffIndex.Alpha)
{
int localMaxBits = codeLengths[0];
int k;
@ -398,7 +412,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
var metadata = new Vp8LMetadata()
{
// TODO: initialize huffman_image_
NumHTreeGroups = numHtreeGroups,
NumHTreeGroups = numHTreeGroups,
HTreeGroups = hTreeGroups,
HuffmanTables = huffmanTables,
};
@ -437,7 +451,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
}
else
{
// (ii)Normal Code Length Code:
// (ii) Normal Code Length Code:
// The code lengths of a Huffman code are read as follows: num_code_lengths specifies the number of code lengths;
// the rest of the code lengths (according to the order in kCodeLengthCodeOrder) are zeros.
var codeLengthCodeLengths = new int[NumCodeLengthCodes];
@ -683,7 +697,8 @@ namespace SixLabors.ImageSharp.Formats.WebP
int xOffset = 8 - (distCode & 0xf);
int dist = (yOffset * xSize) + xOffset;
return (dist >= 1) ? dist : 1; // dist<1 can happen if xsize is very small
// dist < 1 can happen if xsize is very small.
return (dist >= 1) ? dist : 1;
}
private void BuildPackedTable(HTreeGroup hTreeGroup)
@ -727,7 +742,7 @@ namespace SixLabors.ImageSharp.Formats.WebP
return image[(xSize * (y >> bits)) + (x >> bits)];
}
private HTreeGroup[] GetHtreeGroupForPos(Vp8LMetadata metadata, int x, int y)
private HTreeGroup[] GetHTreeGroupForPos(Vp8LMetadata metadata, int x, int y)
{
int metaIndex = this.GetMetaIndex(metadata.HuffmanImage, metadata.HuffmanXSize, metadata.HuffmanSubSampleBits, x, y);
return metadata.HTreeGroups.AsSpan(metaIndex).ToArray();

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