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number of tiles is now part of the options and will be used with the sliding window approach also, so both methods are comparable

pull/673/head
popow 8 years ago
parent
254cd33652
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1981231528
5 changed files with 37 additions and 38 deletions
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  1. 4
      src/ImageSharp/Processing/HistogramEqualizationExtension.cs
  2. 21
      src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationProcessor.cs
  3. 45
      src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationSWProcessor.cs
  4. 4
      src/ImageSharp/Processing/Processors/Normalization/HistogramEqualizationOptions.cs
  5. 1
      src/ImageSharp/Processing/Processors/Normalization/HistogramEqualizationProcessor.cs

4
src/ImageSharp/Processing/HistogramEqualizationExtension.cs
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@ -44,11 +44,11 @@ namespace SixLabors.ImageSharp.Processing
break;
case HistogramEqualizationMethod.Adaptive:
processor = new AdaptiveHistEqualizationProcessor<TPixel>(options.LuminanceLevels, options.ClipHistogram, options.ClipLimitPercentage, options.GridSize);
processor = new AdaptiveHistEqualizationProcessor<TPixel>(options.LuminanceLevels, options.ClipHistogram, options.ClipLimitPercentage, options.Tiles);
break;
case HistogramEqualizationMethod.AdaptiveSlidingWindow:
processor = new AdaptiveHistEqualizationSWProcessor<TPixel>(options.LuminanceLevels, options.ClipHistogram, options.ClipLimitPercentage, options.GridSize);
processor = new AdaptiveHistEqualizationSWProcessor<TPixel>(options.LuminanceLevels, options.ClipHistogram, options.ClipLimitPercentage, options.Tiles);
break;
default:

21
src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationProcessor.cs
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@ -26,19 +26,19 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
/// or 65536 for 16-bit grayscale images.</param>
/// <param name="clipHistogram">Indicating whether to clip the histogram bins at a specific value.</param>
/// <param name="clipLimitPercentage">Histogram clip limit in percent of the total pixels in the grid. Histogram bins which exceed this limit, will be capped at this value.</param>
/// <param name="gridSize">The grid size of the adaptive histogram equalization. Minimum value is 4.</param>
public AdaptiveHistEqualizationProcessor(int luminanceLevels, bool clipHistogram, float clipLimitPercentage, int gridSize)
/// <param name="tiles">The number of tiles the image is split into (horizontal and vertically).</param>
public AdaptiveHistEqualizationProcessor(int luminanceLevels, bool clipHistogram, float clipLimitPercentage, int tiles)
: base(luminanceLevels, clipHistogram, clipLimitPercentage)
{
Guard.MustBeGreaterThanOrEqualTo(gridSize, 4, nameof(gridSize));
Guard.MustBeGreaterThanOrEqualTo(tiles, 0, nameof(tiles));
this.GridSize = gridSize;
this.Tiles = tiles;
}
/// <summary>
/// Gets the size of the grid for the adaptive histogram equalization.
/// Gets the number of tiles the image is split into (horizontal and vertically) for the adaptive histogram equalization.
/// </summary>
public int GridSize { get; }
private int Tiles { get; }
/// <inheritdoc/>
protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration)
@ -47,11 +47,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
int numberOfPixels = source.Width * source.Height;
Span<TPixel> pixels = source.GetPixelSpan();
int numTilesX = 20;
int numTilesY = 20;
int tileWidth = Convert.ToInt32(Math.Ceiling(source.Width / (double)numTilesX));
int tileHeight = Convert.ToInt32(Math.Ceiling(source.Height / (double)numTilesY));
int tileWidth = Convert.ToInt32(Math.Ceiling(source.Width / (double)this.Tiles));
int tileHeight = Convert.ToInt32(Math.Ceiling(source.Height / (double)this.Tiles));
int pixelsInTile = tileWidth * tileHeight;
int halfTileWidth = tileWidth / 2;
int halfTileHeight = tileHeight / 2;
@ -63,7 +60,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
Span<int> cdf = cdfBuffer.GetSpan();
// The image is split up into tiles. For each tile the cumulative distribution function will be calculated.
CdfData[,] cdfData = this.CalculateLookupTables(source, histogram, cdf, numTilesX, numTilesY, tileWidth, tileHeight);
CdfData[,] cdfData = this.CalculateLookupTables(source, histogram, cdf, this.Tiles, this.Tiles, tileWidth, tileHeight);
int tileX = 0;
int tileY = 0;

45
src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationSWProcessor.cs
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@ -25,19 +25,19 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
/// or 65536 for 16-bit grayscale images.</param>
/// <param name="clipHistogram">Indicating whether to clip the histogram bins at a specific value.</param>
/// <param name="clipLimitPercentage">Histogram clip limit in percent of the total pixels in the grid. Histogram bins which exceed this limit, will be capped at this value.</param>
/// <param name="gridSize">The grid size of the adaptive histogram equalization. Minimum value is 4.</param>
public AdaptiveHistEqualizationSWProcessor(int luminanceLevels, bool clipHistogram, float clipLimitPercentage, int gridSize)
/// <param name="tiles">The number of tiles the image is split into (horizontal and vertically).</param>
public AdaptiveHistEqualizationSWProcessor(int luminanceLevels, bool clipHistogram, float clipLimitPercentage, int tiles)
: base(luminanceLevels, clipHistogram, clipLimitPercentage)
{
Guard.MustBeGreaterThanOrEqualTo(gridSize, 4, nameof(gridSize));
Guard.MustBeGreaterThanOrEqualTo(tiles, 0, nameof(tiles));
this.GridSize = gridSize;
this.Tiles = tiles;
}
/// <summary>
/// Gets the size of the grid for the adaptive histogram equalization.
/// Gets the number of tiles the image is split into (horizontal and vertically) for the adaptive histogram equalization.
/// </summary>
public int GridSize { get; }
private int Tiles { get; }
/// <inheritdoc/>
protected override void OnFrameApply(ImageFrame<TPixel> source, Rectangle sourceRectangle, Configuration configuration)
@ -46,8 +46,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
int numberOfPixels = source.Width * source.Height;
Span<TPixel> pixels = source.GetPixelSpan();
int pixelsInGrid = this.GridSize * this.GridSize;
int halfGridSize = this.GridSize / 2;
int tileWidth = source.Width / this.Tiles;
int pixeInTile = tileWidth * tileWidth;
int halfTileWith = tileWidth / 2;
using (Buffer2D<TPixel> targetPixels = configuration.MemoryAllocator.Allocate2D<TPixel>(source.Width, source.Height))
{
ParallelFor.WithConfiguration(
@ -66,9 +67,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
int maxHistIdx = 0;
// Build the histogram of grayscale values for the current grid.
for (int dy = -halfGridSize; dy < halfGridSize; dy++)
for (int dy = -halfTileWith; dy < halfTileWith; dy++)
{
Span<TPixel> rowSpan = this.GetPixelRow(source, (int)x - halfGridSize, dy, this.GridSize);
Span<TPixel> rowSpan = this.GetPixelRow(source, (int)x - halfTileWith, dy, tileWidth);
int maxIdx = this.AddPixelsToHistogram(rowSpan, histogram, this.LuminanceLevels);
if (maxIdx > maxHistIdx)
{
@ -82,12 +83,12 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
{
// Clipping the histogram, but doing it on a copy to keep the original un-clipped values for the next iteration.
histogram.Slice(0, maxHistIdx).CopyTo(histogramCopy);
this.ClipHistogram(histogramCopy, this.ClipLimitPercentage, pixelsInGrid);
this.ClipHistogram(histogramCopy, this.ClipLimitPercentage, pixeInTile);
}
// Calculate the cumulative distribution function, which will map each input pixel in the current grid to a new value.
int cdfMin = this.ClipHistogramEnabled ? this.CalculateCdf(cdf, histogramCopy, maxHistIdx) : this.CalculateCdf(cdf, histogram, maxHistIdx);
float numberOfPixelsMinusCdfMin = pixelsInGrid - cdfMin;
float numberOfPixelsMinusCdfMin = pixeInTile - cdfMin;
// Map the current pixel to the new equalized value
int luminance = this.GetLuminance(source[x, y], this.LuminanceLevels);
@ -95,11 +96,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
targetPixels[x, y].PackFromVector4(new Vector4(luminanceEqualized));
// Remove top most row from the histogram, mirroring rows which exceeds the borders.
Span<TPixel> rowSpan = this.GetPixelRow(source, x - halfGridSize, y - halfGridSize, this.GridSize);
Span<TPixel> rowSpan = this.GetPixelRow(source, x - halfTileWith, y - halfTileWith, tileWidth);
maxHistIdx = this.RemovePixelsFromHistogram(rowSpan, histogram, this.LuminanceLevels, maxHistIdx);
// Add new bottom row to the histogram, mirroring rows which exceeds the borders.
rowSpan = this.GetPixelRow(source, x - halfGridSize, y + halfGridSize, this.GridSize);
rowSpan = this.GetPixelRow(source, x - halfTileWith, y + halfTileWith, tileWidth);
int maxIdx = this.AddPixelsToHistogram(rowSpan, histogram, this.LuminanceLevels);
if (maxIdx > maxHistIdx)
{
@ -119,9 +120,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
/// <param name="source">The source image.</param>
/// <param name="x">The x position.</param>
/// <param name="y">The y position.</param>
/// <param name="gridSize">The grid size.</param>
/// <param name="tileWidth">The width in pixels of a tile.</param>
/// <returns>A pixel row of the length of the grid size.</returns>
private Span<TPixel> GetPixelRow(ImageFrame<TPixel> source, int x, int y, int gridSize)
private Span<TPixel> GetPixelRow(ImageFrame<TPixel> source, int x, int y, int tileWidth)
{
if (y < 0)
{
@ -136,9 +137,9 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
// Special cases for the left and the right border where GetPixelRowSpan can not be used
if (x < 0)
{
var rowPixels = new TPixel[gridSize];
var rowPixels = new TPixel[tileWidth];
int idx = 0;
for (int dx = x; dx < x + gridSize; dx++)
for (int dx = x; dx < x + tileWidth; dx++)
{
rowPixels[idx] = source[Math.Abs(dx), y];
idx++;
@ -146,11 +147,11 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
return rowPixels;
}
else if (x + gridSize > source.Width)
else if (x + tileWidth > source.Width)
{
var rowPixels = new TPixel[gridSize];
var rowPixels = new TPixel[tileWidth];
int idx = 0;
for (int dx = x; dx < x + gridSize; dx++)
for (int dx = x; dx < x + tileWidth; dx++)
{
if (dx >= source.Width)
{
@ -168,7 +169,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
return rowPixels;
}
return source.GetPixelRowSpan(y).Slice(start: x, length: gridSize);
return source.GetPixelRowSpan(y).Slice(start: x, length: tileWidth);
}
/// <summary>

4
src/ImageSharp/Processing/Processors/Normalization/HistogramEqualizationOptions.cs
View File

@ -31,8 +31,8 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
public float ClipLimitPercentage { get; set; } = 0.035f;
/// <summary>
/// Gets or sets the size of the grid for the adaptive histogram equalization. Defaults to 32.
/// Gets or sets the number of tiles the image is split into (horizontal and vertically) for the adaptive histogram equalization. Defaults to 8.
/// </summary>
public int GridSize { get; set; } = 32;
public int Tiles { get; set; } = 8;
}
}

1
src/ImageSharp/Processing/Processors/Normalization/HistogramEqualizationProcessor.cs
View File

@ -20,6 +20,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
/// or 65536 for 16-bit grayscale images.</param>
/// <param name="clipHistogram">Indicates, if histogram bins should be clipped.</param>
/// <param name="clipLimitPercentage">Histogram clip limit in percent of the total pixels in the grid. Histogram bins which exceed this limit, will be capped at this value.</param>
/// <param name="tiles">The number of tiles the image is split into (horizontal and vertically) for the adaptive histogram equalization. Defaults to 8.</param>
protected HistogramEqualizationProcessor(int luminanceLevels, bool clipHistogram, float clipLimitPercentage)
{
Guard.MustBeGreaterThan(luminanceLevels, 0, nameof(luminanceLevels));

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