// Given a Color (RGB Struct) in range of 0-255
// Return H,S,L in range of 0-1
public static void RGB2HSL(ColorRGB rgb, out double h, out double s, out double l)
{
double r = rgb.R / 255.0;
double g = rgb.G / 255.0;
double b = rgb.B / 255.0;
double v;
double m;
double vm;
double r2, g2, b2;
h = 0; // default to black
s = 0;
l = 0;
v = Math.Max(r, g);
v = Math.Max(v, b);
m = Math.Min(r, g);
m = Math.Min(m, b);
l = (m + v) / 2.0;
if(l <= 0.0)
{
return;
}
vm = v - m;
s = vm;
if(s > 0.0)
{
s /= (l <= 0.5) ? (v + m) : (2.0 - v - m);
}
else
{
return;
}
r2 = (v - r) / vm;
g2 = (v - g) / vm;
b2 = (v - b) / vm;
if(r == v)
{
h = (g == m ? 5.0 + b2 : 1.0 - g2);
}
else if(g == v)
{
h = (b == m ? 1.0 + r2 : 3.0 - b2);
}
else
{
h = (r == m ? 3.0 + g2 : 5.0 - r2);
}
h /= 6.0;
}