public static Image DrawHistogramOfOrientedGradients(this Image image, int blockCount, int bucketCount)
{
Contract.Assert(image != null);
Contract.Assert(image.Gradient != null, "gradient is not computed");
Contract.Assert(bucketCount <= 9, "Cannot draw gradient for more than 9 buckets");
ColorPixel[] colorPixel = HOGPixels.getHogPixels();
var histogramSizeX = blockCount;
var histogramSizeY = blockCount;
var bucketAngles = 360 / bucketCount;
byte[,,] gradHist = new byte[histogramSizeX, histogramSizeY, bucketCount + 1];
int angle;
int sizex, sizey, binx, biny;
sizex = (image.PixelWidth / histogramSizeX + 1);
sizey = (image.PixelHeight / histogramSizeY + 1);
for (int i = 0; i < histogramSizeX; i++)
{
for (int j = 0; j < (int)histogramSizeY; j++)
{
for (int k = 0; k < 9; k++)
{
gradHist[i, j, k] = 0;
}
}
}
for (int y = 0; y < image.PixelHeight; y++)
{
for (int x = 0; x < image.PixelWidth; x++)
{
binx = x / sizex;
biny = y / sizey;
angle = image.Gradient[x, y] / bucketAngles;
angle = angle >= bucketCount ? 0 : angle; // is this ok?
gradHist[binx, biny, angle]++;
}
}
for (int y = 0; y < (int)histogramSizeX; y++)
{
for (int x = 0; x < (int)histogramSizeY; x++)
{
var max = 0;
var maxindex = 0;
for (int k = 0; k < bucketCount; k++)
{
if (gradHist[x, y, k] > max)
{
max = gradHist[x, y, k];
maxindex = k;
}
}
gradHist[x, y, bucketCount] = (byte)maxindex;
}
}
for (int y = 0; y < image.PixelHeight; y++)
{
for (int x = 0; x < image.PixelWidth; x++)
{
binx = x / sizex;
biny = y / sizey;
var pixel = colorPixel[gradHist[binx, biny, bucketCount]];
image.GrayScale.SetPixel(x, y, (byte)((pixel.R + pixel.G + pixel.B) / 3)); // coud replace with bucket index times 360/bucketCount
}
}
return(image);
}
public static int[] HistogramOfOrientedGradients(this Image image, int blockCount, int bucketCount)
{
Contract.Assert(image != null);
Contract.Assert(image.Gradient != null, "gradient is not computed");
ColorPixel[] colorPixel = HOGPixels.getHogPixels();
var histogramSizeX = blockCount;
var histogramSizeY = blockCount;
var bucketAngles = (int)Math.Ceiling((decimal)360 / bucketCount);
byte[,,] gradHist = new byte[histogramSizeX, histogramSizeY, bucketCount + 1];
int[] histogram = new int[bucketCount];
int angle;
int sizex, sizey, binx, biny;
sizex = (int)(image.PixelWidth / histogramSizeX + 1);
sizey = (int)(image.PixelHeight / histogramSizeY + 1);
for (int i = 0; i < (int)histogramSizeX; i++)
{
for (int j = 0; j < (int)histogramSizeY; j++)
{
for (int k = 0; k < 9; k++)
{
gradHist[i, j, k] = 0;
}
}
}
// compute gradients for each angle
for (int y = 0; y < image.PixelHeight; y++)
{
for (int x = 0; x < image.PixelWidth; x++)
{
binx = x / sizex;
biny = y / sizey;
angle = image.Gradient[x, y] / bucketAngles;
if (angle >= bucketCount)
{
angle = 0;
}
gradHist[binx, biny, angle]++;
}
}
//compute max gradient
for (int y = 0; y < (int)histogramSizeX; y++)
{
for (int x = 0; x < (int)histogramSizeY; x++)
{
var max = 0;
var maxindex = 0;
for (int k = 0; k < bucketCount; k++)
{
if (gradHist[x, y, k] > max)
{
max = gradHist[x, y, k];
maxindex = k;
}
}
gradHist[x, y, bucketCount] = (byte)maxindex;
}
}
//compute histogram
for (int y = 0; y < image.PixelHeight; y++)
{
for (int x = 0; x < image.PixelWidth; x++)
{
binx = x / sizex;
biny = y / sizey;
histogram[gradHist[binx, biny, bucketCount]] += image.GrayScale.GetPixel(x, y);
}
}
return(histogram);
}
