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simplified interpolation between the tiles

pull/673/head
popow 8 years ago
parent
23661e12d2
commit
176e7e9f83
1 changed files with 34 additions and 19 deletions
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  1. 53
      src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationProcessor.cs

53
src/ImageSharp/Processing/Processors/Normalization/AdaptiveHistEqualizationProcessor.cs
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@ -58,7 +58,7 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
Span<int> histogram = histogramBuffer.GetSpan(); Span<int> histogram = histogramBuffer.GetSpan();
Span<int> cdf = cdfBuffer.GetSpan(); Span<int> cdf = cdfBuffer.GetSpan();
// The image is split up in square tiles of the size of the parameter GridSize. // The image is split up into square tiles of the size of the parameter GridSize.
// For each tile the cumulative distribution function will be calculated. // For each tile the cumulative distribution function will be calculated.
int cdfPosX = 0; int cdfPosX = 0;
int cdfPosY = 0; int cdfPosY = 0;
@ -97,10 +97,10 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
int tilePosX = 0; int tilePosX = 0;
int tilePosY = 0; int tilePosY = 0;
for (int y = halfGridSize; y < source.Height - halfGridSize; y += this.GridSize) for (int y = halfGridSize; y < source.Height - this.GridSize; y += this.GridSize)
{ {
tilePosX = 0; tilePosX = 0;
for (int x = halfGridSize; x < source.Width - halfGridSize; x += this.GridSize) for (int x = halfGridSize; x < source.Width - this.GridSize; x += this.GridSize)
{ {
int gridPosX = 0; int gridPosX = 0;
int gridPosY = 0; int gridPosY = 0;
@ -109,17 +109,24 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
for (int dy = y; dy < ylimit; dy++) for (int dy = y; dy < ylimit; dy++)
{ {
gridPosX = 0; gridPosX = 0;
float ty = gridPosY / (float)(this.GridSize - 1);
int yTop = tilePosY;
int yBottom = yTop + 1;
for (int dx = x; dx < xlimit; dx++) for (int dx = x; dx < xlimit; dx++)
{ {
TPixel sourcePixel = source[dx, dy]; TPixel sourcePixel = source[dx, dy];
int luminace = this.GetLuminance(sourcePixel, this.LuminanceLevels); int luminace = this.GetLuminance(sourcePixel, this.LuminanceLevels);
float cdfLeftTopLuminance = cdfData[tilePosX, tilePosY].RemapGreyValue(luminace, pixelsInGrid); int xLeft = tilePosX;
float cdfRightTopLuminance = cdfData[tilePosX + 1, tilePosY].RemapGreyValue(luminace, pixelsInGrid); int xRight = tilePosX + 1;
float cdfLeftBottomLuminance = cdfData[tilePosX, tilePosY + 1].RemapGreyValue(luminace, pixelsInGrid);
float cdfRightBottomLuminance = cdfData[tilePosX + 1, tilePosY + 1].RemapGreyValue(luminace, pixelsInGrid); float cdfLeftTopLuminance = cdfData[xLeft, yTop].RemapGreyValue(luminace, pixelsInGrid);
float cdfRightTopLuminance = cdfData[xRight, yTop].RemapGreyValue(luminace, pixelsInGrid);
float cdfLeftBottomLuminance = cdfData[xLeft, yBottom].RemapGreyValue(luminace, pixelsInGrid);
float cdfRightBottomLuminance = cdfData[xRight, yBottom].RemapGreyValue(luminace, pixelsInGrid);
float luminanceEqualized = this.BilinearInterpolation(gridPosX, gridPosY, gridPosX / (float)(this.GridSize - 1), ty, cdfLeftTopLuminance, cdfRightTopLuminance, cdfLeftBottomLuminance, cdfRightBottomLuminance);
float luminanceEqualized = this.BilinearInterpolation(gridPosX, gridPosY, this.GridSize, cdfLeftTopLuminance, cdfRightTopLuminance, cdfLeftBottomLuminance, cdfRightBottomLuminance);
pixels[(dy * source.Width) + dx].PackFromVector4(new Vector4(luminanceEqualized)); pixels[(dy * source.Width) + dx].PackFromVector4(new Vector4(luminanceEqualized));
gridPosX++; gridPosX++;
} }
@ -140,20 +147,28 @@ namespace SixLabors.ImageSharp.Processing.Processors.Normalization
/// </summary> /// </summary>
/// <param name="x">X position.</param> /// <param name="x">X position.</param>
/// <param name="y">Y position.</param> /// <param name="y">Y position.</param>
/// <param name="gridSize">The size of the grid.</param> /// <param name="tx">The interpolation value in x direction in the range of [0, 1].</param>
/// <param name="lt">Luminance from tile top left.</param> /// <param name="ty">The interpolation value in y direction in the range of [0, 1].</param>
/// <param name="rt">Luminance from tile right top.</param> /// <param name="lt">Luminance from top left tile.</param>
/// <param name="lb">Luminance from tile left bottom.</param> /// <param name="rt">Luminance from right top tile.</param>
/// <param name="rb">Luminance from tile right bottom.</param> /// <param name="lb">Luminance from left bottom tile.</param>
/// <param name="rb">Luminance from right bottom tile.</param>
/// <returns>Interpolated Luminance.</returns> /// <returns>Interpolated Luminance.</returns>
private float BilinearInterpolation(int x, int y, int gridSize, float lt, float rt, float lb, float rb) private float BilinearInterpolation(int x, int y, float tx, float ty, float lt, float rt, float lb, float rb)
{ {
float r1 = ((gridSize - x) / (float)gridSize * lb) + ((x / (float)gridSize) * rb); return this.LinearInterpolation(this.LinearInterpolation(lt, rt, tx), this.LinearInterpolation(lb, rb, tx), ty);
float r2 = ((gridSize - x) / (float)gridSize * lt) + ((x / (float)gridSize) * rt); }
float res = ((y / ((float)gridSize)) * r1) + (((y - gridSize) / (float)(-gridSize)) * r2);
return res; /// <summary>
/// Linear interpolation between two grey values.
/// </summary>
/// <param name="left">The left value.</param>
/// <param name="right">The right value.</param>
/// <param name="t">The interpolation value between the two values in the range of [0, 1].</param>
/// <returns>The interpolated value.</returns>
private float LinearInterpolation(float left, float right, float t)
{
return left + ((right - left) * t);
} }
private class CdfData private class CdfData

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