#include “stdafx.h”
#define min3v(v1, v2, v3)   ((v1)>(v2)? ((v2)>(v3)?(v3):(v2)):((v1)>(v3)?(v3):(v2)))
#define max3v(v1, v2, v3)   ((v1)<(v2)? ((v2)<(v3)?(v3):(v2)):((v1)<(v3)?(v3):(v1)))
typedef struct
{
    BYTE  red;              // [0,255]
    BYTE  green;            // [0,255]
    BYTE  blue;             // [0,255]

}COLOR_RGB;

typedef struct
{
    float hue;              // [0,360]
    float saturation;       // [0,100]
    float luminance;        // [0,100]
}COLOR_HSL;

// Converts RGB to HSL

static void RGBtoHSL(/ [in]/const COLOR_RGB rgb, /[out]*/COLOR_HSL hsl)
{
    float h=0, s=0, l=0;
    // normalizes red-green-blue values
    float r = rgb->red/255.f;
    float g = rgb->green/255.f;
    float b = rgb->blue/255.f;
    float maxVal = max3v(r, g, b);
    float minVal = min3v(r, g, b);

    // hue

    if(maxVal == minVal)
    {
        h = 0; // undefined
    }

    else if(maxVal==r && g>=b)
    {
        h = 60.0f(g-b)/(maxVal-minVal);
    }

    else if(maxVal==r && g<b)
    {
        h = 60.0f (g-b)/(maxVal-minVal) + 360.0f;
    }

    else if(maxVal==g)
    {
        h = 60.0f(b-r)/(maxVal-minVal) + 120.0f;
    }
    else if(maxVal==b)
    {
        h = 60.0f*(r-g)/(maxVal-minVal) + 240.0f;
    }

    // luminance

    l = (maxVal+minVal)/2.0f;
    // saturation

    if(l == 0 || maxVal == minVal)
    {
        s = 0;
    }

    else if(0<l && l<=0.5f)
    {
        s = (maxVal-minVal)/(maxVal+minVal);
    }
    else if(l>0.5f)
    {
        s = (maxVal-minVal)/(2 - (maxVal+minVal)); //(maxVal-minVal > 0)?
    }
    hsl->hue = (h>360)? 360 : ((h<0)?0:h);
    hsl->saturation = ((s>1)? 1 : ((s<0)?0:s))*100;
    hsl->luminance = ((l>1)? 1 : ((l<0)?0:l))*100;
}
// Converts HSL to RGB

static void HSLtoRGB(const COLOR_HSL *hsl, COLOR_RGB *rgb)
{
    float h = hsl->hue;                  // h must be [0, 360]
    float s = hsl->saturation/100.f; // s must be [0, 1]
    float l = hsl->luminance/100.f;      // l must be [0, 1]
    float R, G, B;

    if(hsl->saturation == 0)
    {
        // achromatic color (gray scale)
        R = G = B = l*255.f;

else
    {
        float q = (l<0.5f)?(l * (1.0f+s)):(l+s - (l*s));
        float p = (2.0f * l) - q;
        float Hk = h/360.0f;
        float T[3];
        T[0] = Hk + 0.f; // Tr   0.f=1.0/3.0
        T[1] = Hk;              // Tb
        T[2] = Hk - 0.f; // Tg

        for(int i=0; i<3; i++)
        {
            if(T[i] < 0) T[i] += 1.0f;
            if(T[i] > 1) T[i] -= 1.0f;

            if((T[i]*6) < 1)
            {
                T[i] = p + ((q-p)*6.0f*T[i]);
            }
            else if((T[i]*2.0f) < 1) //(1.0/6.0)<=T[i] && T[i]<0.5
            {
                T[i] = q;
            }
            else if((T[i]*3.0f) < 2) // 0.5<=T[i] && T[i]<(2.0/3.0)
            {
                T[i] = p + (q-p) * ((2.0f/3.0f) - T[i]) * 6.0f;
            }
            else T[i] = p;
        }
        R = T[0]*255.0f;
        G = T[1]*255.0f;
        B = T[2] 255.0f;

    }
    rgb->red = (BYTE)((R>255)? 255 : ((R<0)?0 : R));
    rgb->green = (BYTE)((G>255)? 255 : ((G<0)?0 : G));
    rgb->blue = (BYTE)((B>255)? 255 : ((B<0)?0 : B));

}
int _tmain(int argc, _TCHAR argv[])
{
    COLOR_RGB  rgb={254, 216, 166};
    COLOR_HSL  hsl;
    RGBtoHSL(&rgb, &hsl);
    printf(“H=%.0f; S=%.0f; L=%.0f “, hsl.hue, hsl.saturation, hsl.luminance);
    HSLtoRGB(&hsl, &rgb);
    RGBtoHSL(&rgb, &hsl);
    printf(“H=%.0f; S=%.0f; L=%.0f “, hsl.hue, hsl.saturation, hsl.luminance);
    getchar();
    return 0;

}