RGB to HSI
R = rgbData[y, x, 0];
G = rgbData[y, x, 1];
B = rgbData[y, x, 2];
r = (double)R / (R + G + B);
g = (double)G / (R + G + B);
b = (double)B / (R + G + B);
value1 = 0.5 * ((r - g) + (r - b));
value2 = Math.Pow((Math.Pow(r - g, 2) + (r - b) * (g - b)), 0.5);
radial = Math.Acos(value1 / value2);
theta = (int)(radial * 180.0 / Math.PI);
if (!double.IsNaN(theta))
h = (b > g) ? (360 - theta) : theta;
else
h = 0;
s = 1 - 3 * CompareRGB.Min(r, g, b);
if (double.IsNaN(s))
s = 0;
i = (R + G + B) / 3.0;
HSI to RGB
