RGB空间与HSV空间的相互转换（C++实现，修正网上大多数的代码错误）

void Rgb2Hsv(float R, float G, float B, float& H, float& S, float&V)
{
     // r,g,b values are from 0 to 1
    // h = [0,360], s = [0,1], v = [0,1]
    // if s == 0, then h = -1 (undefined)
    float min, max, delta,tmp;
    tmp = R>G?G:R;
    min = tmp>B?B:tmp;
    tmp = R>G?R:G;
    max = tmp>B?tmp:B;
    V = max; // v
    delta = max - min;
    if( max !=  )
        S = delta / max; // s
    else
    {
        // r = g = b = 0 // s = 0, v is undefined
        S = ;
        H = ;
        return;
    }
    if (delta == ){
        H = ;
        return;
    }
    else if(R == max){
        if (G >= B)
            H = (G - B) / delta; // between yellow & magenta
        else
            H = (G - B) / delta + 6.0;
    }
    else if( G == max )
        H = 2.0 + ( B - R ) / delta; // between cyan & yellow
    else if (B == max)
        H = 4.0 + ( R - G ) / delta; // between magenta & cyan
    H *= 60.0; // degrees
}

源地址：http://blog.****.net/shijun_zhang/article/details/6525388