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Split up Vp8 and Vp8L Histogram

pull/1552/head
Brian Popow 5 years ago
parent
8d7d68f626
commit
f873859a75
3 changed files with 138 additions and 134 deletions
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  1. 128
      src/ImageSharp/Formats/WebP/Lossless/Vp8LHistogram.cs
  2. 12
      src/ImageSharp/Formats/WebP/Lossy/Vp8EncIterator.cs
  3. 132
      src/ImageSharp/Formats/WebP/Lossy/Vp8Histogram.cs

128
src/ImageSharp/Formats/WebP/Lossless/Vp8LHistogram.cs
View File

@ -3,7 +3,6 @@
using System;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
namespace SixLabors.ImageSharp.Formats.Webp.Lossless
{
@ -11,22 +10,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless
{
private const uint NonTrivialSym = 0xffffffff;
/// <summary>
/// Size of histogram used by CollectHistogram.
/// </summary>
private const int MaxCoeffThresh = 31;
private int maxValue;
private int lastNonZero;
/// <summary>
/// Initializes a new instance of the <see cref="Vp8LHistogram"/> class.
/// </summary>
public Vp8LHistogram()
{
}
/// <summary>
/// Initializes a new instance of the <see cref="Vp8LHistogram"/> class.
/// </summary>
@ -317,114 +300,6 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless
return true;
}
public void CollectHistogram(Span<byte> reference, Span<byte> pred, int startBlock, int endBlock)
{
int j;
var distribution = new int[MaxCoeffThresh + 1];
for (j = startBlock; j < endBlock; ++j)
{
var output = new short[16];
this.Vp8FTransform(reference.Slice(WebpLookupTables.Vp8DspScan[j]), pred.Slice(WebpLookupTables.Vp8DspScan[j]), output);
// Convert coefficients to bin.
for (int k = 0; k < 16; ++k)
{
int v = Math.Abs(output[k]) >> 3;
int clippedValue = ClipMax(v, MaxCoeffThresh);
++distribution[clippedValue];
}
}
this.SetHistogramData(distribution);
}
public int GetAlpha()
{
// 'alpha' will later be clipped to [0..MAX_ALPHA] range, clamping outer
// values which happen to be mostly noise. This leaves the maximum precision
// for handling the useful small values which contribute most.
int maxValue = this.maxValue;
int lastNonZero = this.lastNonZero;
int alpha = (maxValue > 1) ? WebpConstants.AlphaScale * lastNonZero / maxValue : 0;
return alpha;
}
public void Merge(Vp8LHistogram other)
{
if (this.maxValue > other.maxValue)
{
other.maxValue = this.maxValue;
}
if (this.lastNonZero > other.lastNonZero)
{
other.lastNonZero = this.lastNonZero;
}
}
private void SetHistogramData(int[] distribution)
{
int maxValue = 0;
int lastNonZero = 1;
for (int k = 0; k <= MaxCoeffThresh; ++k)
{
int value = distribution[k];
if (value > 0)
{
if (value > maxValue)
{
maxValue = value;
}
lastNonZero = k;
}
}
this.maxValue = maxValue;
this.lastNonZero = lastNonZero;
}
private void Vp8FTransform(Span<byte> src, Span<byte> reference, Span<short> output)
{
int i;
var tmp = new int[16];
for (i = 0; i < 4; ++i)
{
int d0 = src[0] - reference[0]; // 9bit dynamic range ([-255,255])
int d1 = src[1] - reference[1];
int d2 = src[2] - reference[2];
int d3 = src[3] - reference[3];
int a0 = d0 + d3; // 10b [-510,510]
int a1 = d1 + d2;
int a2 = d1 - d2;
int a3 = d0 - d3;
tmp[0 + (i * 4)] = (a0 + a1) * 8; // 14b [-8160,8160]
tmp[1 + (i * 4)] = ((a2 * 2217) + (a3 * 5352) + 1812) >> 9; // [-7536,7542]
tmp[2 + (i * 4)] = (a0 - a1) * 8;
tmp[3 + (i * 4)] = ((a3 * 2217) - (a2 * 5352) + 937) >> 9;
// Do not change the span in the last iteration.
if (i < 3)
{
src = src.Slice(WebpConstants.Bps);
reference = reference.Slice(WebpConstants.Bps);
}
}
for (i = 0; i < 4; ++i)
{
int a0 = tmp[0 + i] + tmp[12 + i]; // 15b
int a1 = tmp[4 + i] + tmp[8 + i];
int a2 = tmp[4 + i] - tmp[8 + i];
int a3 = tmp[0 + i] - tmp[12 + i];
output[0 + i] = (short)((a0 + a1 + 7) >> 4); // 12b
output[4 + i] = (short)((((a2 * 2217) + (a3 * 5352) + 12000) >> 16) + ((a3 != 0) ? 1 : 0));
output[8 + i] = (short)((a0 - a1 + 7) >> 4);
output[12 + i] = (short)(((a3 * 2217) - (a2 * 5352) + 51000) >> 16);
}
}
private void AddLiteral(Vp8LHistogram b, Vp8LHistogram output, int literalSize)
{
if (this.IsUsed[0])
@ -636,8 +511,5 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossless
output[i] = a[i] + b[i];
}
}
[MethodImpl(InliningOptions.ShortMethod)]
private static int ClipMax(int v, int max) => (v > max) ? max : v;
}
}

12
src/ImageSharp/Formats/WebP/Lossy/Vp8EncIterator.cs
View File

@ -2,7 +2,7 @@
// Licensed under the Apache License, Version 2.0.
using System;
using SixLabors.ImageSharp.Formats.Webp.Lossless;
using SixLabors.ImageSharp.Formats.WebP.Lossy;
namespace SixLabors.ImageSharp.Formats.Webp.Lossy
{
@ -383,7 +383,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
this.MakeLuma16Preds();
for (mode = 0; mode < maxMode; ++mode)
{
var histo = new Vp8LHistogram();
var histo = new Vp8Histogram();
histo.CollectHistogram(this.YuvIn.AsSpan(YOffEnc), this.YuvP.AsSpan(Vp8Encoding.Vp8I16ModeOffsets[mode]), 0, 16);
int alpha = histo.GetAlpha();
if (alpha > bestAlpha)
@ -402,21 +402,21 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
byte[] modes = new byte[16];
int maxMode = MaxIntra4Mode;
int i4Alpha;
var totalHisto = new Vp8LHistogram();
var totalHisto = new Vp8Histogram();
int curHisto = 0;
this.StartI4();
do
{
int mode;
int bestModeAlpha = DefaultAlpha;
var histos = new Vp8LHistogram[2];
var histos = new Vp8Histogram[2];
Span<byte> src = this.YuvIn.AsSpan(YOffEnc + WebpLookupTables.Vp8Scan[this.I4]);
this.MakeIntra4Preds();
for (mode = 0; mode < maxMode; ++mode)
{
int alpha;
histos[curHisto] = new Vp8LHistogram();
histos[curHisto] = new Vp8Histogram();
histos[curHisto].CollectHistogram(src, this.YuvP.AsSpan(Vp8Encoding.Vp8I4ModeOffsets[mode]), 0, 1);
alpha = histos[curHisto].GetAlpha();
@ -456,7 +456,7 @@ namespace SixLabors.ImageSharp.Formats.Webp.Lossy
this.MakeChroma8Preds();
for (mode = 0; mode < maxMode; ++mode)
{
var histo = new Vp8LHistogram();
var histo = new Vp8Histogram();
histo.CollectHistogram(this.YuvIn.AsSpan(UOffEnc), this.YuvP.AsSpan(Vp8Encoding.Vp8UvModeOffsets[mode]), 16, 16 + 4 + 4);
int alpha = histo.GetAlpha();
if (alpha > bestAlpha)

132
src/ImageSharp/Formats/WebP/Lossy/Vp8Histogram.cs
View File

@ -0,0 +1,132 @@
// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.
using System;
using System.Runtime.CompilerServices;
using SixLabors.ImageSharp.Formats.Webp;
namespace SixLabors.ImageSharp.Formats.WebP.Lossy
{
internal class Vp8Histogram
{
/// <summary>
/// Size of histogram used by CollectHistogram.
/// </summary>
private const int MaxCoeffThresh = 31;
private int maxValue;
private int lastNonZero;
public int GetAlpha()
{
// 'alpha' will later be clipped to [0..MAX_ALPHA] range, clamping outer
// values which happen to be mostly noise. This leaves the maximum precision
// for handling the useful small values which contribute most.
int maxValue = this.maxValue;
int lastNonZero = this.lastNonZero;
int alpha = (maxValue > 1) ? WebpConstants.AlphaScale * lastNonZero / maxValue : 0;
return alpha;
}
public void CollectHistogram(Span<byte> reference, Span<byte> pred, int startBlock, int endBlock)
{
int j;
int[] distribution = new int[MaxCoeffThresh + 1];
for (j = startBlock; j < endBlock; ++j)
{
short[] output = new short[16];
this.Vp8FTransform(reference.Slice(WebpLookupTables.Vp8DspScan[j]), pred.Slice(WebpLookupTables.Vp8DspScan[j]), output);
// Convert coefficients to bin.
for (int k = 0; k < 16; ++k)
{
int v = Math.Abs(output[k]) >> 3;
int clippedValue = ClipMax(v, MaxCoeffThresh);
++distribution[clippedValue];
}
}
this.SetHistogramData(distribution);
}
public void Merge(Vp8Histogram other)
{
if (this.maxValue > other.maxValue)
{
other.maxValue = this.maxValue;
}
if (this.lastNonZero > other.lastNonZero)
{
other.lastNonZero = this.lastNonZero;
}
}
private void SetHistogramData(int[] distribution)
{
int maxValue = 0;
int lastNonZero = 1;
for (int k = 0; k <= MaxCoeffThresh; ++k)
{
int value = distribution[k];
if (value > 0)
{
if (value > maxValue)
{
maxValue = value;
}
lastNonZero = k;
}
}
this.maxValue = maxValue;
this.lastNonZero = lastNonZero;
}
private void Vp8FTransform(Span<byte> src, Span<byte> reference, Span<short> output)
{
int i;
int[] tmp = new int[16];
for (i = 0; i < 4; ++i)
{
int d0 = src[0] - reference[0]; // 9bit dynamic range ([-255,255])
int d1 = src[1] - reference[1];
int d2 = src[2] - reference[2];
int d3 = src[3] - reference[3];
int a0 = d0 + d3; // 10b [-510,510]
int a1 = d1 + d2;
int a2 = d1 - d2;
int a3 = d0 - d3;
tmp[0 + (i * 4)] = (a0 + a1) * 8; // 14b [-8160,8160]
tmp[1 + (i * 4)] = ((a2 * 2217) + (a3 * 5352) + 1812) >> 9; // [-7536,7542]
tmp[2 + (i * 4)] = (a0 - a1) * 8;
tmp[3 + (i * 4)] = ((a3 * 2217) - (a2 * 5352) + 937) >> 9;
// Do not change the span in the last iteration.
if (i < 3)
{
src = src.Slice(WebpConstants.Bps);
reference = reference.Slice(WebpConstants.Bps);
}
}
for (i = 0; i < 4; ++i)
{
int a0 = tmp[0 + i] + tmp[12 + i]; // 15b
int a1 = tmp[4 + i] + tmp[8 + i];
int a2 = tmp[4 + i] - tmp[8 + i];
int a3 = tmp[0 + i] - tmp[12 + i];
output[0 + i] = (short)((a0 + a1 + 7) >> 4); // 12b
output[4 + i] = (short)((((a2 * 2217) + (a3 * 5352) + 12000) >> 16) + ((a3 != 0) ? 1 : 0));
output[8 + i] = (short)((a0 - a1 + 7) >> 4);
output[12 + i] = (short)(((a3 * 2217) - (a2 * 5352) + 51000) >> 16);
}
}
[MethodImpl(InliningOptions.ShortMethod)]
private static int ClipMax(int v, int max) => (v > max) ? max : v;
}
}
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