rgb<--->hsb

rgb2hsb

/// <summary> 
/// HSB用float数据类型表示 
/// </summary> 
static void RGB2HSB(int r, int g, int b, out float hue, out float sat, out float bri) 
{ 
    int minval = Math.Min(r, Math.Min(g, b)); 
    int maxval = Math.Max(r, Math.Max(g, b)); 

    //bri 
    bri = (float)(maxval + minval) / 510; 

    //sat 
    if (maxval == minval) 
    { 
        sat = 0.0f; 
    } 
    else 
    { 
        int sum = maxval + minval; 

        if (sum > 255) 
        { 
            sum = 510 - sum; 
        } 

        sat = (float)(maxval - minval) / sum; 
    } 

    //hue 
    if (maxval == minval) 
    { 
        hue = 0.0f; 
    } 
    else 
    { 
        float diff = (float)(maxval - minval); 
        float rnorm = (maxval - r) / diff; 
        float gnorm = (maxval - g) / diff; 
        float bnorm = (maxval - b) / diff; 

        hue = 0.0f; 

        if (r == maxval) 
        { 
            hue = 60.0f * (6.0f + bnorm - gnorm); 
        } 

        if (g == maxval) 
        { 
            hue = 60.0f * (2.0f + rnorm - bnorm); 
        } 

        if (b == maxval) 
        { 
            hue = 60.0f * (4.0f + gnorm - rnorm); 
        } 

        if (hue > 360.0f) 
        { 
            hue = hue - 360.0f; 
        } 
    } 
} 

/// <summary> 
/// HSB用int数据类型表示，同Winform中的ColorDialog中HSB的表示 
/// </summary> 
static void RGB2HSB(int r, int g, int b, out int hue, out int sat, out int bri) 
{ 
    float fHue, fSat, fBri; 

    RGB2HSB(r, g, b, out fHue, out fSat, out fBri); 

    hue = (int)((fHue / 360.0f) * 240 + 0.5); 
    sat = (int)(fSat * 241 + 0.5); 
    bri = (int)(fBri * 241 + 0.5); 

    if (hue > 239) 
    { 
        hue = 239; 
    } 

    if (sat > 240) 
    { 
        sat = 240; 
    } 

    if (bri > 240) 
    { 
        bri = 240; 
    } 
} 

/// <summary> 
/// 传入的HSB用int型表示，如果用float型表示，可将下面的转换成float过程去掉 
/// </summary> 
static void HSB2RGB(int hue, int sat, int bri, out int r, out  int g, out int b) 
{ 
    //begin:HSB转换为float 
    if (hue > 239) 
    { 
        hue = 239; 
    } 
    else 
    { 
        if (hue < 0) 
        { 
            hue = 0; 
        } 
    } 

    if (sat > 240) 
    { 
        sat = 240; 
    } 
    else 
    { 
        if (sat < 0) 
        { 
            sat = 0; 
        } 
    } 

    if (bri > 240) 
    { 
        bri = 240; 
    } 
    else 
    { 
        if (bri < 0) 
        { 
            bri = 0; 
        } 
    } 

    float H = hue / 239.0f; 
    float S = sat / 240.0f; 
    float L = bri / 240.0f; 

    //end:HSB转换为float 

    float red = 0, green = 0, blue = 0; 
    float d1, d2; 

    if (L == 0) 
    { 
        red = green = blue = 0; 
    } 
    else 
    { 
        if (S == 0) 
        { 
            red = green = blue = L; 
        } 
        else 
        { 
            d2 = (L <= 0.5f) ? L * (1.0f + S) : L + S - (L * S); 
            d1 = 2.0f * L - d2; 

            float[] d3 = new float[] { H + 1.0f / 3.0f, H, H - 1.0f / 3.0f }; 
            float[] rgb = new float[] { 0, 0, 0 }; 

            for (int i = 0; i < 3; i++) 
            { 
                if (d3[i] < 0) 
                { 
                    d3[i] += 1.0f; 
                } 

                if (d3[i] > 1.0f) 
                { 
                    d3[i] -= 1.0f; 
                } 

                if (6.0f * d3[i] < 1.0f) 
                { 
                    rgb[i] = d1 + (d2 - d1) * d3[i] * 6.0f; 
                } 
                else 
                { 
                    if (2.0f * d3[i] < 1.0f) 
                    { 
                        rgb[i] = d2; 
                    } 
                    else 
                    { 
                        if (3.0f * d3[i] < 2.0f) 
                        { 
                            rgb[i] = (d1 + (d2 - d1) * ((2.0f / 3.0f) - d3[i]) * 6.0f); 
                        } 
                        else 
                        { 
                            rgb[i] = d1; 
                        } 
                    } 
                } 
            } 

            red = rgb[0]; 
            green = rgb[1]; 
            blue = rgb[2]; 
        } 
    } 

    red = 255.0f * red; 
    green = 255.0f * green; 
    blue = 255.0f * blue; 

    if (red < 1) 
    { 
        red = 0.0f; 
    } 
    else 
    { 
        if (red > 255.0f) 
        { 
            red = 255.0f; 
        } 
    } 

    if (green < 1) 
    { 
        green = 0.0f; 
    } 
    else 
    { 
        if (green > 255.0f) 
        { 
            green = 255.0f; 
        } 
    } 

    if (blue < 1) 
    { 
        blue = 0.0f; 
    } 
    else 
    { 
        if (blue > 255.0f) 
        { 
            blue = 255.0f; 
        } 
    } 

    r = (int)(red + 0.5); 
    g = (int)(green + 0.5); 
    b = (int)(blue + 0.5); 
} 

颜色转化时由于int跟float强制转换以及精度表示等原因，会产生误差。如一个RGB转换为HSB再转换为RGB会于原RGB有一定的误差。