// Conversion from RGB to CIELAB, using illuminant D65.
public static LabColor ToLab(this Color color)
{
// RGB are assumed to be in [0...255] range
double R = color.R / 255d;
double G = color.G / 255d;
double B = color.B / 255d;
// CIEXYZ coordinates are normalized to [0...1]
double x = 0.4124564 * R + 0.3575761 * G + 0.1804375 * B;
double y = 0.2126729 * R + 0.7151522 * G + 0.0721750 * B;
double z = 0.0193339 * R + 0.1191920 * G + 0.9503041 * B;
double xRatio = x / XN;
double yRatio = y / YN;
double zRatio = z / ZN;
LabColor result = new LabColor {
// L is normalized to [0...100]
L = 116 * XyzToLab(yRatio) - 16,
a = 500 * (XyzToLab(xRatio) - XyzToLab(yRatio)),
b = 200 * (XyzToLab(yRatio) - XyzToLab(zRatio))
};
return(result);
}
static double GetSingleValue(SortingTask task, int x, int y)
{
Color c = task.OriginalImage.GetPixel(x, y);
switch (task.Metric)
{
case SortMetric.Intensity:
return(c.GetIntensity());
case SortMetric.Lightness:
return(c.GetLightness());
case SortMetric.Value:
return(Math.Max(c.R, Math.Max(c.G, c.B)));
case SortMetric.Luma:
return(c.R * 0.2126 + c.G * 0.7152 + c.B * 0.0722);
case SortMetric.HslHue:
return(c.GetHue() / 360d);
case SortMetric.LabHue: {
LabColor labC = c.ToLab();
if (labC.a == 0)
{
return(Math.PI / 2);
}
else
{
double lh = Math.Atan2(labC.b, labC.a);
if (lh <= 0)
{
lh = Math.PI * 2 - Math.Abs(lh);
}
return(lh);
}
}
case SortMetric.Chroma:
return(c.GetChroma());
case SortMetric.LabChroma: {
LabColor labColor = c.ToLab();
return(Math.Sqrt(labColor.a * labColor.a + labColor.b * labColor.b));
}
case SortMetric.HsbSaturation: {
double chroma = c.GetChroma();
if (chroma == 0)
{
return(0);
}
else
{
return(chroma / c.GetMax());
}
}
case SortMetric.HsiSaturation: {
double chroma = c.GetChroma();
double intensity = c.GetIntensity();
if (chroma == 0 || intensity == 0)
{
return(0);
}
else
{
double m = c.GetMin();
return(1 - m / intensity);
}
}
case SortMetric.HslSaturation: {
double max = c.GetMax();
double min = c.GetMin();
double chroma = c.GetChroma();
double L = c.GetLightness();
if (chroma == 0 || L == 0 || L == 1)
{
return(0);
}
if (L < 0.5)
{
return(chroma / (max + min));
}
else
{
return(chroma / (2 - max - min));
}
}
case SortMetric.LabSaturation: {
LabColor labColor = c.ToLab();
if (labColor.L < ColorUtil.LinearThreshold)
{
return(0);
}
else
{
return(Math.Sqrt(labColor.a * labColor.a + labColor.b * labColor.b) / labColor.L);
}
}
case SortMetric.RedChannel:
return(c.R);
case SortMetric.GreenChannel:
return(c.G);
case SortMetric.BlueChannel:
return(c.B);
case SortMetric.Red:
return(c.R - Math.Max(c.G, c.B));
case SortMetric.Green:
return(c.G - Math.Max(c.R, c.B));
case SortMetric.Blue:
return(c.B - Math.Max(c.R, c.G));
case SortMetric.Cyan:
return((c.G + c.B) - Math.Max(c.R * 1.5, Math.Abs(c.G - c.B)));
case SortMetric.Magenta:
return((c.R + c.B) - Math.Max(c.G * 1.5, Math.Abs(c.R - c.B)));
case SortMetric.Yellow:
return((c.R + c.G) - Math.Max(c.B * 1.5, Math.Abs(c.R - c.G)));
case SortMetric.LabA:
return(c.ToLab().a);
case SortMetric.LabB:
return(c.ToLab().b);
default:
throw new ArgumentOutOfRangeException();
}
}
