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Merge pull request #1431 from SixLabors/bp/fix1429
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Use GetPixelRowSpan to access pixel data in Histogram equalization
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@brianpopow
brianpopow authored Nov 16, 2020
2 parents dea0737 + 9bed14f commit f77801e
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Showing 3 changed files with 83 additions and 40 deletions.
62 changes: 26 additions & 36 deletions ...arp/Processing/Processors/Normalization/AdaptiveHistogramEqualizationProcessor{TPixel}.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,42 +86,39 @@ protected override void OnFrameApply(ImageFrame<TPixel> source)
new Rectangle(0, 0, sourceWidth, tileYStartPositions.Count),
in operation);

ref TPixel pixelsBase = ref source.GetPixelReference(0, 0);

// Fix left column
ProcessBorderColumn(ref pixelsBase, cdfData, 0, sourceWidth, sourceHeight, this.Tiles, tileHeight, xStart: 0, xEnd: halfTileWidth, luminanceLevels);
ProcessBorderColumn(source, cdfData, 0, sourceHeight, this.Tiles, tileHeight, xStart: 0, xEnd: halfTileWidth, luminanceLevels);

// Fix right column
int rightBorderStartX = ((this.Tiles - 1) * tileWidth) + halfTileWidth;
ProcessBorderColumn(ref pixelsBase, cdfData, this.Tiles - 1, sourceWidth, sourceHeight, this.Tiles, tileHeight, xStart: rightBorderStartX, xEnd: sourceWidth, luminanceLevels);
ProcessBorderColumn(source, cdfData, this.Tiles - 1, sourceHeight, this.Tiles, tileHeight, xStart: rightBorderStartX, xEnd: sourceWidth, luminanceLevels);

// Fix top row
ProcessBorderRow(ref pixelsBase, cdfData, 0, sourceWidth, this.Tiles, tileWidth, yStart: 0, yEnd: halfTileHeight, luminanceLevels);
ProcessBorderRow(source, cdfData, 0, sourceWidth, this.Tiles, tileWidth, yStart: 0, yEnd: halfTileHeight, luminanceLevels);

// Fix bottom row
int bottomBorderStartY = ((this.Tiles - 1) * tileHeight) + halfTileHeight;
ProcessBorderRow(ref pixelsBase, cdfData, this.Tiles - 1, sourceWidth, this.Tiles, tileWidth, yStart: bottomBorderStartY, yEnd: sourceHeight, luminanceLevels);
ProcessBorderRow(source, cdfData, this.Tiles - 1, sourceWidth, this.Tiles, tileWidth, yStart: bottomBorderStartY, yEnd: sourceHeight, luminanceLevels);

// Left top corner
ProcessCornerTile(ref pixelsBase, cdfData, sourceWidth, 0, 0, xStart: 0, xEnd: halfTileWidth, yStart: 0, yEnd: halfTileHeight, luminanceLevels);
ProcessCornerTile(source, cdfData, 0, 0, xStart: 0, xEnd: halfTileWidth, yStart: 0, yEnd: halfTileHeight, luminanceLevels);

// Left bottom corner
ProcessCornerTile(ref pixelsBase, cdfData, sourceWidth, 0, this.Tiles - 1, xStart: 0, xEnd: halfTileWidth, yStart: bottomBorderStartY, yEnd: sourceHeight, luminanceLevels);
ProcessCornerTile(source, cdfData, 0, this.Tiles - 1, xStart: 0, xEnd: halfTileWidth, yStart: bottomBorderStartY, yEnd: sourceHeight, luminanceLevels);

// Right top corner
ProcessCornerTile(ref pixelsBase, cdfData, sourceWidth, this.Tiles - 1, 0, xStart: rightBorderStartX, xEnd: sourceWidth, yStart: 0, yEnd: halfTileHeight, luminanceLevels);
ProcessCornerTile(source, cdfData, this.Tiles - 1, 0, xStart: rightBorderStartX, xEnd: sourceWidth, yStart: 0, yEnd: halfTileHeight, luminanceLevels);

// Right bottom corner
ProcessCornerTile(ref pixelsBase, cdfData, sourceWidth, this.Tiles - 1, this.Tiles - 1, xStart: rightBorderStartX, xEnd: sourceWidth, yStart: bottomBorderStartY, yEnd: sourceHeight, luminanceLevels);
ProcessCornerTile(source, cdfData, this.Tiles - 1, this.Tiles - 1, xStart: rightBorderStartX, xEnd: sourceWidth, yStart: bottomBorderStartY, yEnd: sourceHeight, luminanceLevels);
}
}

/// <summary>
/// Processes the part of a corner tile which was previously left out. It consists of 1 / 4 of a tile and does not need interpolation.
/// </summary>
/// <param name="pixelsBase">The output pixels base reference.</param>
/// <param name="source">The source image.</param>
/// <param name="cdfData">The lookup table to remap the grey values.</param>
/// <param name="sourceWidth">The source image width.</param>
/// <param name="cdfX">The x-position in the CDF lookup map.</param>
/// <param name="cdfY">The y-position in the CDF lookup map.</param>
/// <param name="xStart">X start position.</param>
Expand All @@ -133,9 +130,8 @@ protected override void OnFrameApply(ImageFrame<TPixel> source)
/// or 65536 for 16-bit grayscale images.
/// </param>
private static void ProcessCornerTile(
ref TPixel pixelsBase,
ImageFrame<TPixel> source,
CdfTileData cdfData,
int sourceWidth,
int cdfX,
int cdfY,
int xStart,
Expand All @@ -146,10 +142,10 @@ private static void ProcessCornerTile(
{
for (int dy = yStart; dy < yEnd; dy++)
{
int dyOffSet = dy * sourceWidth;
Span<TPixel> rowSpan = source.GetPixelRowSpan(dy);
for (int dx = xStart; dx < xEnd; dx++)
{
ref TPixel pixel = ref Unsafe.Add(ref pixelsBase, dyOffSet + dx);
ref TPixel pixel = ref rowSpan[dx];
float luminanceEqualized = cdfData.RemapGreyValue(cdfX, cdfY, GetLuminance(pixel, luminanceLevels));
pixel.FromVector4(new Vector4(luminanceEqualized, luminanceEqualized, luminanceEqualized, pixel.ToVector4().W));
}
Expand All @@ -159,10 +155,9 @@ private static void ProcessCornerTile(
/// <summary>
/// Processes a border column of the image which is half the size of the tile width.
/// </summary>
/// <param name="pixelBase">The output pixels reference.</param>
/// <param name="source">The source image.</param>
/// <param name="cdfData">The pre-computed lookup tables to remap the grey values for each tiles.</param>
/// <param name="cdfX">The X index of the lookup table to use.</param>
/// <param name="sourceWidth">The source image width.</param>
/// <param name="sourceHeight">The source image height.</param>
/// <param name="tileCount">The number of vertical tiles.</param>
/// <param name="tileHeight">The height of a tile.</param>
Expand All @@ -173,10 +168,9 @@ private static void ProcessCornerTile(
/// or 65536 for 16-bit grayscale images.
/// </param>
private static void ProcessBorderColumn(
ref TPixel pixelBase,
ImageFrame<TPixel> source,
CdfTileData cdfData,
int cdfX,
int sourceWidth,
int sourceHeight,
int tileCount,
int tileHeight,
Expand All @@ -194,10 +188,10 @@ private static void ProcessBorderColumn(
int tileY = 0;
for (int dy = y; dy < yLimit; dy++)
{
int dyOffSet = dy * sourceWidth;
Span<TPixel> rowSpan = source.GetPixelRowSpan(dy);
for (int dx = xStart; dx < xEnd; dx++)
{
ref TPixel pixel = ref Unsafe.Add(ref pixelBase, dyOffSet + dx);
ref TPixel pixel = ref rowSpan[dx];
float luminanceEqualized = InterpolateBetweenTwoTiles(pixel, cdfData, cdfX, cdfY, cdfX, cdfY + 1, tileY, tileHeight, luminanceLevels);
pixel.FromVector4(new Vector4(luminanceEqualized, luminanceEqualized, luminanceEqualized, pixel.ToVector4().W));
}
Expand All @@ -213,7 +207,7 @@ private static void ProcessBorderColumn(
/// <summary>
/// Processes a border row of the image which is half of the size of the tile height.
/// </summary>
/// <param name="pixelBase">The output pixels base reference.</param>
/// <param name="source">The source image.</param>
/// <param name="cdfData">The pre-computed lookup tables to remap the grey values for each tiles.</param>
/// <param name="cdfY">The Y index of the lookup table to use.</param>
/// <param name="sourceWidth">The source image width.</param>
Expand All @@ -226,7 +220,7 @@ private static void ProcessBorderColumn(
/// or 65536 for 16-bit grayscale images.
/// </param>
private static void ProcessBorderRow(
ref TPixel pixelBase,
ImageFrame<TPixel> source,
CdfTileData cdfData,
int cdfY,
int sourceWidth,
Expand All @@ -244,12 +238,12 @@ private static void ProcessBorderRow(
{
for (int dy = yStart; dy < yEnd; dy++)
{
int dyOffSet = dy * sourceWidth;
Span<TPixel> rowSpan = source.GetPixelRowSpan(dy);
int tileX = 0;
int xLimit = Math.Min(x + tileWidth, sourceWidth - 1);
for (int dx = x; dx < xLimit; dx++)
{
ref TPixel pixel = ref Unsafe.Add(ref pixelBase, dyOffSet + dx);
ref TPixel pixel = ref rowSpan[dx];
float luminanceEqualized = InterpolateBetweenTwoTiles(pixel, cdfData, cdfX, cdfY, cdfX + 1, cdfY, tileX, tileWidth, luminanceLevels);
pixel.FromVector4(new Vector4(luminanceEqualized, luminanceEqualized, luminanceEqualized, pixel.ToVector4().W));
tileX++;
Expand Down Expand Up @@ -410,8 +404,6 @@ public RowIntervalOperation(
[MethodImpl(InliningOptions.ShortMethod)]
public void Invoke(in RowInterval rows)
{
ref TPixel sourceBase = ref this.source.GetPixelReference(0, 0);

for (int index = rows.Min; index < rows.Max; index++)
{
(int y, int cdfY) tileYStartPosition = this.tileYStartPositions[index];
Expand All @@ -427,11 +419,11 @@ public void Invoke(in RowInterval rows)
int xEnd = Math.Min(x + this.tileWidth, this.sourceWidth);
for (int dy = y; dy < yEnd; dy++)
{
int dyOffSet = dy * this.sourceWidth;
Span<TPixel> rowSpan = this.source.GetPixelRowSpan(dy);
int tileX = 0;
for (int dx = x; dx < xEnd; dx++)
{
ref TPixel pixel = ref Unsafe.Add(ref sourceBase, dyOffSet + dx);
ref TPixel pixel = ref rowSpan[dx];
float luminanceEqualized = InterpolateBetweenFourTiles(
pixel,
this.cdfData,
Expand Down Expand Up @@ -597,15 +589,13 @@ public RowIntervalOperation(
[MethodImpl(InliningOptions.ShortMethod)]
public void Invoke(in RowInterval rows)
{
ref TPixel sourceBase = ref this.source.GetPixelReference(0, 0);

for (int index = rows.Min; index < rows.Max; index++)
{
int cdfX = 0;
int cdfY = this.tileYStartPositions[index].cdfY;
int y = this.tileYStartPositions[index].y;
int endY = Math.Min(y + this.tileHeight, this.sourceHeight);
ref int cdfMinBase = ref MemoryMarshal.GetReference(this.cdfMinBuffer2D.GetRowSpan(cdfY));
Span<int> cdfMinSpan = this.cdfMinBuffer2D.GetRowSpan(cdfY);

using IMemoryOwner<int> histogramBuffer = this.allocator.Allocate<int>(this.luminanceLevels);
Span<int> histogram = histogramBuffer.GetSpan();
Expand All @@ -620,10 +610,10 @@ public void Invoke(in RowInterval rows)
int xlimit = Math.Min(x + this.tileWidth, this.sourceWidth);
for (int dy = y; dy < endY; dy++)
{
int dyOffset = dy * this.sourceWidth;
Span<TPixel> rowSpan = this.source.GetPixelRowSpan(dy);
for (int dx = x; dx < xlimit; dx++)
{
int luminance = GetLuminance(Unsafe.Add(ref sourceBase, dyOffset + dx), this.luminanceLevels);
int luminance = GetLuminance(rowSpan[dx], this.luminanceLevels);
histogram[luminance]++;
}
}
Expand All @@ -633,7 +623,7 @@ public void Invoke(in RowInterval rows)
this.processor.ClipHistogram(histogram, this.processor.ClipLimit);
}

Unsafe.Add(ref cdfMinBase, cdfX) = this.processor.CalculateCdf(ref cdfBase, ref histogramBase, histogram.Length - 1);
cdfMinSpan[cdfX] += this.processor.CalculateCdf(ref cdfBase, ref histogramBase, histogram.Length - 1);

cdfX++;
}
Expand Down
8 changes: 4 additions & 4 deletions ...Sharp/Processing/Processors/Normalization/GlobalHistogramEqualizationProcessor{TPixel}.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -116,13 +116,13 @@ public GrayscaleLevelsRowOperation(
public void Invoke(int y)
{
ref int histogramBase = ref MemoryMarshal.GetReference(this.histogramBuffer.GetSpan());
ref TPixel pixelBase = ref MemoryMarshal.GetReference(this.source.GetPixelRowSpan(y));
Span<TPixel> pixelRow = this.source.GetPixelRowSpan(y);
int levels = this.luminanceLevels;

for (int x = 0; x < this.bounds.Width; x++)
{
// TODO: We should bulk convert here.
var vector = Unsafe.Add(ref pixelBase, x).ToVector4();
var vector = pixelRow[x].ToVector4();
int luminance = ImageMaths.GetBT709Luminance(ref vector, levels);
Interlocked.Increment(ref Unsafe.Add(ref histogramBase, luminance));
}
Expand Down Expand Up @@ -165,14 +165,14 @@ public CdfApplicationRowOperation(
public void Invoke(int y)
{
ref int cdfBase = ref MemoryMarshal.GetReference(this.cdfBuffer.GetSpan());
ref TPixel pixelBase = ref MemoryMarshal.GetReference(this.source.GetPixelRowSpan(y));
Span<TPixel> pixelRow = this.source.GetPixelRowSpan(y);
int levels = this.luminanceLevels;
float noOfPixelsMinusCdfMin = this.numberOfPixelsMinusCdfMin;

for (int x = 0; x < this.bounds.Width; x++)
{
// TODO: We should bulk convert here.
ref TPixel pixel = ref Unsafe.Add(ref pixelBase, x);
ref TPixel pixel = ref pixelRow[x];
var vector = pixel.ToVector4();
int luminance = ImageMaths.GetBT709Luminance(ref vector, levels);
float luminanceEqualized = Unsafe.Add(ref cdfBase, luminance) / noOfPixelsMinusCdfMin;
Expand Down
53 changes: 53 additions & 0 deletions tests/ImageSharp.Benchmarks/Processing/HistogramEqualization.cs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,53 @@
// Copyright (c) Six Labors.
// Licensed under the Apache License, Version 2.0.

using System.IO;
using BenchmarkDotNet.Attributes;
using SixLabors.ImageSharp.PixelFormats;
using SixLabors.ImageSharp.Processing;
using SixLabors.ImageSharp.Processing.Processors.Normalization;
using SixLabors.ImageSharp.Tests;

namespace SixLabors.ImageSharp.Benchmarks.Processing
{
[Config(typeof(Config.ShortClr))]
public class HistogramEqualization : BenchmarkBase
{
private Image<Rgba32> image;

[GlobalSetup]
public void ReadImages()
{
if (this.image == null)
{
this.image = Image.Load<Rgba32>(File.OpenRead(Path.Combine(TestEnvironment.InputImagesDirectoryFullPath, TestImages.Jpeg.Baseline.HistogramEqImage)));
}
}

[GlobalCleanup]
public void Cleanup()
{
this.image.Dispose();
}

[Benchmark(Description = "Global Histogram Equalization")]
public void GlobalHistogramEqualization()
{
this.image.Mutate(img => img.HistogramEqualization(new HistogramEqualizationOptions()
{
LuminanceLevels = 256,
Method = HistogramEqualizationMethod.Global
}));
}

[Benchmark(Description = "AdaptiveHistogramEqualization (Tile interpolation)")]
public void AdaptiveHistogramEqualization()
{
this.image.Mutate(img => img.HistogramEqualization(new HistogramEqualizationOptions()
{
LuminanceLevels = 256,
Method = HistogramEqualizationMethod.AdaptiveTileInterpolation
}));
}
}
}

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