/// <summary>
/// Stretch HSV histogram to create new image
/// </summary>
public static unsafe Bitmap HistogramStretchHSV(Bitmap image, Rectangle rect)
{
Bitmap dest = (Bitmap)image.Clone();
BitmapData srcDat = image.LockBits(rect, ImageLockMode.ReadOnly, image.PixelFormat);
BitmapData dstDat = dest.LockBits(rect, ImageLockMode.ReadWrite, dest.PixelFormat);
int width = rect.Width;
int height = rect.Height;
int stride = srcDat.Stride;
// get pixel size
int pixelSize = (image.PixelFormat == PixelFormat.Format24bppRgb) ? 3 : 4;
int offset = stride - width * pixelSize;
// do the job
byte *src = (byte *)srcDat.Scan0.ToPointer();
byte *dst = (byte *)dstDat.Scan0.ToPointer();
int pix_num = width * height; //縦×横
int[] num_b = new int[512];
int min_per, max_per;
int per1 = pix_num / 100;
int per99 = pix_num / 100 * 99;
int[] aryH = new int[pix_num];
int[] aryS = new int[pix_num];
int[] aryV = new int[pix_num];
int maxH, maxS, maxV;
int minV;
maxH = maxS = maxV = 0;
minV = 255;
int tmp_pix, last_pix;
double ratio;
int pos;
int count_i = 0;
int sum = 0;
RGB rgb = new RGB();
HSV hsv = new HSV();
// RGB histograms
// for each row
for (int y = 0; y < height; y++)
{
// for each pixel
for (int x = 0; x < width; x++, src += pixelSize)
{
rgb.Red = src[RGB.R];
rgb.Green = src[RGB.G];
rgb.Blue = src[RGB.B];
hsv = HSV.FromRGB(rgb);
pos = y * width + x;
aryH[pos] = hsv.Hue;
aryS[pos] = hsv.Saturation;
aryV[pos] = hsv.Value;
if (hsv.Hue > maxH)
{
maxH = hsv.Hue;
}
if (hsv.Saturation > maxS)
{
maxS = hsv.Saturation;
}
if (hsv.Value > maxV)
{
maxV = hsv.Value;
}
if (hsv.Value < minV)
{
minV = hsv.Value;
}
}
src += offset;
}
// histogram
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++, src += pixelSize)
{
num_b[aryV[y * width + x]]++;
}
}
do
{
sum += num_b[count_i++];
} while (sum < per1);
min_per = count_i - 1;
do
{
sum += num_b[count_i++];
} while (sum < per99);
max_per = count_i - 1;
ratio = (double)(511.0 / (max_per - min_per));
// stretch histogram
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++, src += pixelSize)
{
pos = y * width + x;
tmp_pix = aryV[pos];
if (tmp_pix <= min_per)
{
last_pix = 0;
}
else if (tmp_pix >= max_per)
{
last_pix = 511;
}
else
{
last_pix = (int)((tmp_pix - min_per) * ratio);
}
if (last_pix < 0)
{
aryV[pos] = 0;
}
else if (last_pix >= 511)
{
aryV[pos] = 511;
}
else
{
aryV[pos] = last_pix;
}
}
}
// for each row
for (int y = 0; y < height; y++)
{
// for each pixel
for (int x = 0; x < width; x++, src += pixelSize, dst += pixelSize)
{
pos = y * width + x;
hsv.Hue = aryH[pos];
hsv.Saturation = aryS[pos];
hsv.Value = aryV[pos];
HSV.ToRGB(hsv, rgb);
dst[RGB.R] = rgb.Red;
dst[RGB.G] = rgb.Green;
dst[RGB.B] = rgb.Blue;
}
src += offset;
dst += offset;
}
image.UnlockBits(srcDat);
dest.UnlockBits(dstDat);
return(dest);
}
