/// <summary>
/// Convert from RGB to YCbCr color space (Rec 601-1 specification).
/// </summary>
///
/// <param name="rgb">Source color in <b>RGB</b> color space.</param>
///
/// <returns>Returns <see cref="YCbCr"/> instance, which represents converted color value.</returns>
///
public static YCbCr FromRGB(RGB rgb)
{
YCbCr ycbcr = new YCbCr( );
FromRGB(rgb, ycbcr);
return(ycbcr);
}
/// <summary>
/// Convert from RGB to YCbCr color space (Rec 601-1 specification).
/// </summary>
///
/// <param name="rgb">Source color in <b>RGB</b> color space.</param>
/// <param name="ycbcr">Destination color in <b>YCbCr</b> color space.</param>
///
public static void FromRGB(RGB rgb, YCbCr ycbcr)
{
float r = (float)rgb.Red / 255;
float g = (float)rgb.Green / 255;
float b = (float)rgb.Blue / 255;
ycbcr.Y = (float)(0.2989 * r + 0.5866 * g + 0.1145 * b);
ycbcr.Cb = (float)(-0.1687 * r - 0.3313 * g + 0.5000 * b);
ycbcr.Cr = (float)(0.5000 * r - 0.4184 * g - 0.0816 * b);
}
/// <summary>
/// Convert from YCbCr to RGB color space.
/// </summary>
///
/// <param name="ycbcr">Source color in <b>YCbCr</b> color space.</param>
/// <param name="rgb">Destination color in <b>RGB</b> color spacs.</param>
///
public static void ToRGB(YCbCr ycbcr, RGB rgb)
{
// don't warry about zeros. compiler will remove them
float r = Math.Max(0.0f, Math.Min(1.0f, (float)(ycbcr.Y + 0.0000 * ycbcr.Cb + 1.4022 * ycbcr.Cr)));
float g = Math.Max(0.0f, Math.Min(1.0f, (float)(ycbcr.Y - 0.3456 * ycbcr.Cb - 0.7145 * ycbcr.Cr)));
float b = Math.Max(0.0f, Math.Min(1.0f, (float)(ycbcr.Y + 1.7710 * ycbcr.Cb + 0.0000 * ycbcr.Cr)));
rgb.Red = (byte)(r * 255);
rgb.Green = (byte)(g * 255);
rgb.Blue = (byte)(b * 255);
rgb.Alpha = 255;
}
// Gather statistics for the specified image
private unsafe void ProcessImage(UnmanagedImage image, byte *mask, int maskLineSize)
{
// get image dimension
int width = image.Width;
int height = image.Height;
pixels = pixelsWithoutBlack = 0;
int[] yhisto = new int[256];
int[] cbhisto = new int[256];
int[] crhisto = new int[256];
int[] yhistoWB = new int[256];
int[] cbhistoWB = new int[256];
int[] crhistoWB = new int[256];
RGB rgb = new RGB( );
YCbCr ycbcr = new YCbCr( );
int pixelSize = (image.PixelFormat == PixelFormat.Format24bppRgb) ? 3 : 4;
int offset = image.Stride - width * pixelSize;
int maskOffset = maskLineSize - width;
// do the job
byte *p = (byte *)image.ImageData.ToPointer( );
if (mask == null)
{
// for each line
for (int y = 0; y < height; y++)
{
// for each pixel
for (int x = 0; x < width; x++, p += pixelSize)
{
rgb.Red = p[RGB.R];
rgb.Green = p[RGB.G];
rgb.Blue = p[RGB.B];
// convert to YCbCr color space
AForgeCore.Imaging.YCbCr.FromRGB(rgb, ycbcr);
yhisto[(int)(ycbcr.Y * 255)]++;
cbhisto[(int)((ycbcr.Cb + 0.5) * 255)]++;
crhisto[(int)((ycbcr.Cr + 0.5) * 255)]++;
pixels++;
if ((ycbcr.Y != 0.0) || (ycbcr.Cb != 0.0) || (ycbcr.Cr != 0.0))
{
yhistoWB[(int)(ycbcr.Y * 255)]++;
cbhistoWB[(int)((ycbcr.Cb + 0.5) * 255)]++;
crhistoWB[(int)((ycbcr.Cr + 0.5) * 255)]++;
pixelsWithoutBlack++;
}
}
p += offset;
}
}
else
{
// for each line
for (int y = 0; y < height; y++)
{
// for each pixel
for (int x = 0; x < width; x++, p += pixelSize, mask++)
{
if (*mask == 0)
{
continue;
}
rgb.Red = p[RGB.R];
rgb.Green = p[RGB.G];
rgb.Blue = p[RGB.B];
// convert to YCbCr color space
AForgeCore.Imaging.YCbCr.FromRGB(rgb, ycbcr);
yhisto[(int)(ycbcr.Y * 255)]++;
cbhisto[(int)((ycbcr.Cb + 0.5) * 255)]++;
crhisto[(int)((ycbcr.Cr + 0.5) * 255)]++;
pixels++;
if ((ycbcr.Y != 0.0) || (ycbcr.Cb != 0.0) || (ycbcr.Cr != 0.0))
{
yhistoWB[(int)(ycbcr.Y * 255)]++;
cbhistoWB[(int)((ycbcr.Cb + 0.5) * 255)]++;
crhistoWB[(int)((ycbcr.Cr + 0.5) * 255)]++;
pixelsWithoutBlack++;
}
}
p += offset;
mask += maskOffset;
}
}
// create histograms
yHistogram = new ContinuousHistogram(yhisto, new Range(0.0f, 1.0f));
cbHistogram = new ContinuousHistogram(cbhisto, new Range(-0.5f, 0.5f));
crHistogram = new ContinuousHistogram(crhisto, new Range(-0.5f, 0.5f));
yHistogramWithoutBlack = new ContinuousHistogram(yhistoWB, new Range(0.0f, 1.0f));
cbHistogramWithoutBlack = new ContinuousHistogram(cbhistoWB, new Range(-0.5f, 0.5f));
crHistogramWithoutBlack = new ContinuousHistogram(crhistoWB, new Range(-0.5f, 0.5f));
}