HSIカラー空間への変換(oF)

HSI testApp::RGBtoHSI(unsigned char r, unsigned char g, unsigned char b)
{
HSI hsi = {0.0f, 0.0f, 0.0f};

unsigned char max, min;

// get Max
if (r > g) max = r;
else max = g;
if (b > max) max = b;
// get Min
if (r < g) min = r;
else min = g;
if (b < min) min = b;

if (max == min) {
    hsi.h = -1.0f;
    hsi.s = 0.0f;
    hsi.i = (float)max / 255.0f;
    return hsi;
}

// calc Hue
if (max == r) 
    hsi.h = (float)(M_PI/3 * (((float)g - b)/(max - min)));
else if (max == g)
    hsi.h = (float)(M_PI/3 * (((float)b - r)/(max - min)) + 2 * M_PI / 3);
else if (max == b)
    hsi.h = (float)(M_PI/3 * (((float)r - g)/(max - min)) + 4 * M_PI / 3);
if (hsi.h < 0.0f) hsi.h += 2 * M_PI;

// calc Saturation
hsi.s = (max - min) / max;

// calc Intensity
hsi.i = max / 255.0f;

return hsi;

}