/// <inheritdoc/>
protected override void OnFrameApply(ImageFrame <TPixel> source)
{
int sourceWidth = source.Width;
int sourceHeight = source.Height;
int tileWidth = (int)MathF.Ceiling(sourceWidth / (float)this.Tiles);
int tileHeight = (int)MathF.Ceiling(sourceHeight / (float)this.Tiles);
int tileCount = this.Tiles;
int halfTileWidth = tileWidth / 2;
int halfTileHeight = tileHeight / 2;
int luminanceLevels = this.LuminanceLevels;
// The image is split up into tiles. For each tile the cumulative distribution function will be calculated.
using (var cdfData = new CdfTileData(this.Configuration, sourceWidth, sourceHeight, this.Tiles, this.Tiles, tileWidth, tileHeight, luminanceLevels))
{
cdfData.CalculateLookupTables(source, this);
var tileYStartPositions = new List <(int y, int cdfY)>();
int cdfY = 0;
int yStart = halfTileHeight;
for (int tile = 0; tile < tileCount - 1; tile++)
{
tileYStartPositions.Add((yStart, cdfY));
cdfY++;
yStart += tileHeight;
}
var operation = new RowIntervalOperation(cdfData, tileYStartPositions, tileWidth, tileHeight, tileCount, halfTileWidth, luminanceLevels, source);
ParallelRowIterator.IterateRowIntervals(
this.Configuration,
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);
// 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);
// Fix top row
ProcessBorderRow(ref pixelsBase, 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);
// Left top corner
ProcessCornerTile(ref pixelsBase, cdfData, sourceWidth, 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);
// Right top corner
ProcessCornerTile(ref pixelsBase, cdfData, sourceWidth, 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);
}
/// <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="source">The source image.</param>
/// <param name="cdfData">The lookup table to remap the grey values.</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>
/// <param name="xEnd">X end position.</param>
/// <param name="yStart">Y start position.</param>
/// <param name="yEnd">Y end position.</param>
/// <param name="luminanceLevels">
/// The number of different luminance levels. Typical values are 256 for 8-bit grayscale images
/// or 65536 for 16-bit grayscale images.
/// </param>
private static void ProcessCornerTile(
ImageFrame <TPixel> source,
CdfTileData cdfData,
int cdfX,
int cdfY,
int xStart,
int xEnd,
int yStart,
int yEnd,
int luminanceLevels)
{
for (int dy = yStart; dy < yEnd; dy++)
{
Span <TPixel> rowSpan = source.GetPixelRowSpan(dy);
for (int dx = xStart; dx < xEnd; 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));
}
}
/// <inheritdoc/>
protected override void OnFrameApply(ImageFrame <TPixel> source)
{
int sourceWidth = source.Width;
int sourceHeight = source.Height;
int tileWidth = (int)MathF.Ceiling(sourceWidth / (float)this.Tiles);
int tileHeight = (int)MathF.Ceiling(sourceHeight / (float)this.Tiles);
int tileCount = this.Tiles;
int halfTileWidth = tileWidth / 2;
int halfTileHeight = tileHeight / 2;
int luminanceLevels = this.LuminanceLevels;
// The image is split up into tiles. For each tile the cumulative distribution function will be calculated.
using (var cdfData = new CdfTileData(this.Configuration, sourceWidth, sourceHeight, this.Tiles, this.Tiles, tileWidth, tileHeight, luminanceLevels))
{
cdfData.CalculateLookupTables(source, this);
var tileYStartPositions = new List <(int y, int cdfY)>();
int cdfY = 0;
int yStart = halfTileHeight;
for (int tile = 0; tile < tileCount - 1; tile++)
{
tileYStartPositions.Add((yStart, cdfY));
cdfY++;
yStart += tileHeight;
}
Parallel.For(
0,
tileYStartPositions.Count,
new ParallelOptions {
MaxDegreeOfParallelism = this.Configuration.MaxDegreeOfParallelism
},
index =>
{
int y = tileYStartPositions[index].y;
int cdfYY = tileYStartPositions[index].cdfY;
// It's unfortunate that we have to do this per iteration.
ref TPixel sourceBase = ref source.GetPixelReference(0, 0);
int cdfX = 0;
int x = halfTileWidth;
for (int tile = 0; tile < tileCount - 1; tile++)
{
int tileY = 0;
int yEnd = Math.Min(y + tileHeight, sourceHeight);
int xEnd = Math.Min(x + tileWidth, sourceWidth);
for (int dy = y; dy < yEnd; dy++)
{
int dyOffSet = dy * sourceWidth;
int tileX = 0;
for (int dx = x; dx < xEnd; dx++)
{
ref TPixel pixel = ref Unsafe.Add(ref sourceBase, dyOffSet + dx);
float luminanceEqualized = InterpolateBetweenFourTiles(
pixel,
cdfData,
tileCount,
tileCount,
tileX,
tileY,
cdfX,
cdfYY,
tileWidth,
tileHeight,
luminanceLevels);
pixel.FromVector4(new Vector4(luminanceEqualized, luminanceEqualized, luminanceEqualized, pixel.ToVector4().W));
tileX++;
}
tileY++;
}
cdfX++;
x += tileWidth;
}
});