tsai
/
ImageSharp
mirror of https://github.com/SixLabors/ImageSharp
1
0
Fork 0
Code Issues Projects Releases Wiki Activity
Browse Source

Moving sliding window from left to right instead of from top to bottom

pull/673/head
Brian Popow 7 years ago
parent
f2930c75d3
commit
8f19e5edd2
1 changed files with 49 additions and 46 deletions
Whitespace
Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL
Split View
Diff Options
Show Stats Download Patch File Download Diff File
  1. 95
      src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationSWProcessor.cs

95
src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationSWProcessor.cs
View File

@ -51,21 +51,22 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
Span<TPixel> pixels = source.GetPixelSpan();
var parallelOptions = new ParallelOptions() { MaxDegreeOfParallelism = configuration.MaxDegreeOfParallelism };
int tileWidth = source.Width / this.Tiles;
int pixeInTile = tileWidth * tileWidth;
int halfTileWith = tileWidth / 2;
int tileHeight = source.Height / this.Tiles;
int pixeInTile = tileHeight * tileHeight;
int halfTileHeight = tileHeight / 2;
int halfTileWidth = halfTileHeight;
using (Buffer2D<TPixel> targetPixels = configuration.MemoryAllocator.Allocate2D<TPixel>(source.Width, source.Height))
{
Parallel.For(
0,
source.Width,
source.Height,
parallelOptions,
x =>
y =>
{
using (IMemoryOwner<int> histogramBuffer = memoryAllocator.Allocate<int>(this.LuminanceLevels, AllocationOptions.Clean))
using (IMemoryOwner<int> histogramBufferCopy = memoryAllocator.Allocate<int>(this.LuminanceLevels, AllocationOptions.Clean))
using (IMemoryOwner<int> cdfBuffer = memoryAllocator.Allocate<int>(this.LuminanceLevels, AllocationOptions.Clean))
using (IMemoryOwner<TPixel> pixelRowBuffer = memoryAllocator.Allocate<TPixel>(tileWidth, AllocationOptions.Clean))
using (IMemoryOwner<TPixel> pixelColumnBuffer = memoryAllocator.Allocate<TPixel>(tileHeight, AllocationOptions.Clean))
{
Span<int> histogram = histogramBuffer.GetSpan();
ref int histogramBase = ref MemoryMarshal.GetReference(histogram);
@ -73,21 +74,21 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
ref int histogramCopyBase = ref MemoryMarshal.GetReference(histogramCopy);
ref int cdfBase = ref MemoryMarshal.GetReference(cdfBuffer.GetSpan());
Span<TPixel> pixelRow = pixelRowBuffer.GetSpan();
Span<TPixel> pixelColumn = pixelColumnBuffer.GetSpan();
int maxHistIdx = 0;
// Build the histogram of grayscale values for the current tile.
for (int dy = -halfTileWith; dy < halfTileWith; dy++)
for (int dx = -halfTileWidth; dx < halfTileWidth; dx++)
{
Span<TPixel> rowSpan = this.GetPixelRow(source, pixelRow, x - halfTileWith, dy, tileWidth);
int maxIdx = this.AddPixelsToHistogram(rowSpan, histogram, this.LuminanceLevels);
Span<TPixel> columnSpan = this.GetPixelColumn(source, pixelColumn, dx, y - halfTileHeight, tileHeight);
int maxIdx = this.AddPixelsToHistogram(columnSpan, histogram, this.LuminanceLevels);
if (maxIdx > maxHistIdx)
{
maxHistIdx = maxIdx;
}
}
for (int y = 0; y < source.Height; y++)
for (int x = 0; x < source.Width; x++)
{
if (this.ClipHistogramEnabled)
{
@ -103,18 +104,18 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
float numberOfPixelsMinusCdfMin = pixeInTile - cdfMin;
// Map the current pixel to the new equalized value
// Map the current pixel to the new equalized value.
int luminance = GetLuminance(source[x, y], this.LuminanceLevels);
float luminanceEqualized = Unsafe.Add(ref cdfBase, luminance) / numberOfPixelsMinusCdfMin;
targetPixels[x, y].FromVector4(new Vector4(luminanceEqualized, luminanceEqualized, luminanceEqualized, source[x, y].ToVector4().W));
// Remove top most row from the histogram, mirroring rows which exceeds the borders.
Span<TPixel> rowSpan = this.GetPixelRow(source, pixelRow, x - halfTileWith, y - halfTileWith, tileWidth);
maxHistIdx = this.RemovePixelsFromHistogram(rowSpan, histogram, this.LuminanceLevels, maxHistIdx);
// Remove left most column from the histogram, mirroring columns which exceeds the borders of the image.
Span<TPixel> columnSpan = this.GetPixelColumn(source, pixelColumn, x - halfTileWidth, y - halfTileHeight, tileHeight);
maxHistIdx = this.RemovePixelsFromHistogram(columnSpan, histogram, this.LuminanceLevels, maxHistIdx);
// Add new bottom row to the histogram, mirroring rows which exceeds the borders.
rowSpan = this.GetPixelRow(source, pixelRow, x - halfTileWith, y + halfTileWith, tileWidth);
int maxIdx = this.AddPixelsToHistogram(rowSpan, histogram, this.LuminanceLevels);
// Add new right column to the histogram, mirroring columns which exceeds the borders of the image.
columnSpan = this.GetPixelColumn(source, pixelColumn, x + halfTileWidth, y - halfTileHeight, tileHeight);
int maxIdx = this.AddPixelsToHistogram(columnSpan, histogram, this.LuminanceLevels);
if (maxIdx > maxHistIdx)
{
maxHistIdx = maxIdx;
@ -128,62 +129,64 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
}
/// <summary>
/// Get the a pixel row at a given position with a length of the tile width. Mirrors pixels which exceeds the edges.
/// Get the a pixel column at a given position with the size of the tile height. Mirrors pixels which exceeds the edges of the image.
/// </summary>
/// <param name="source">The source image.</param>
/// <param name="rowPixels">Pre-allocated pixel row span of the size of a tile width.</param>
/// <param name="columnPixels">Pre-allocated pixel row span of the size of a tile height.</param>
/// <param name="x">The x position.</param>
/// <param name="y">The y position.</param>
/// <param name="tileWidth">The width in pixels of a tile.</param>
/// <param name="tileHeight">The height in pixels of a tile.</param>
/// <returns>A pixel row of the length of the tile width.</returns>
private Span<TPixel> GetPixelRow(ImageFrame<TPixel> source, Span<TPixel> rowPixels, int x, int y, int tileWidth)
private Span<TPixel> GetPixelColumn(ImageFrame<TPixel> source, Span<TPixel> columnPixels, int x, int y, int tileHeight)
{
if (y < 0)
if (x < 0)
{
y = Math.Abs(y);
x = Math.Abs(x);
}
else if (y >= source.Height)
else if (x >= source.Width)
{
int diff = y - source.Height;
y = source.Height - diff - 1;
int diff = x - source.Width;
x = source.Width - diff - 1;
}
// Special cases for the left and the right border where GetPixelRowSpan can not be used
if (x < 0)
int idx = 0;
columnPixels.Clear();
if (y < 0)
{
rowPixels.Clear();
int idx = 0;
for (int dx = x; dx < x + tileWidth; dx++)
columnPixels.Clear();
for (int dy = y; dy < y + tileHeight; dy++)
{
rowPixels[idx] = source[Math.Abs(dx), y];
columnPixels[idx] = source[x, Math.Abs(dy)];
idx++;
}
return rowPixels;
}
else if (x + tileWidth > source.Width)
else if (y + tileHeight > source.Height)
{
rowPixels.Clear();
int idx = 0;
for (int dx = x; dx < x + tileWidth; dx++)
for (int dy = y; dy < y + tileHeight; dy++)
{
if (dx >= source.Width)
if (dy >= source.Height)
{
int diff = dx - source.Width;
rowPixels[idx] = source[dx - diff - 1, y];
int diff = dy - source.Height;
columnPixels[idx] = source[x, dy - diff - 1];
}
else
{
rowPixels[idx] = source[dx, y];
columnPixels[idx] = source[x, dy];
}
idx++;
}
return rowPixels;
}
else
{
for (int dy = y; dy < y + tileHeight; dy++)
{
columnPixels[idx] = source[x, dy];
idx++;
}
}
return source.GetPixelRowSpan(y).Slice(start: x, length: tileWidth);
return columnPixels;
}
/// <summary>

Write Preview
Loading…
Cancel
Save