File content as of revision 0:a81364d9a67b:

#include "mbed.h"
#include "colorspace.h"
#include "math.h"

#define max(a,b) ((a)>(b)?(a):(b))
#define min(a,b) ((a)>(b)?(b):(a))

static float threeway_max(float a, float b, float c) {
    return max(a, max(b, c));
}


static float threeway_min(float a, float b, float c) {
    return min(a, min(b, c));
}


static float hue2rgb(float p, float q, float t) {
    if(t < 0) t += 1;
    if(t > 1) t -= 1;
    if(t < 1/6.0f) return p + (q - p) * 6 * t;
    if(t < 1/2.0f) return q;
    if(t < 2/3.0f) return p + (q - p) * (2/3.0f - t) * 6;
    return p;
}


void hsl2rgb(const FloatHSL *hsl, FloatRGB *rgb)
{
    float h = hsl->h;
    float s = hsl->s;
    float l = hsl->l;
    
    if (s == 0) {
        rgb->r = rgb->g = rgb->b = l; // achromatic
    } else {
        float q = l < 0.5f ? l * (1 + s) : l + s - l * s;
        float p = 2 * l - q;
        rgb->r = hue2rgb(p, q, h + 1/3.0f);
        rgb->g = hue2rgb(p, q, h);
        rgb->b = hue2rgb(p, q, h - 1/3.0f);
    }
}


void hsv2rgb(const FloatHSV *hsv, FloatRGB *rgb)
{
    float r, g, b;

    int i = floor(hsv->h * 6);
    float f = hsv->h * 6 - i;
    float p = hsv->v * (1 - hsv->s);
    float q = hsv->v * (1 - f * hsv->s);
    float t = hsv->v * (1 - (1 - f) * hsv->s);

    switch(i % 6) {
        case 0:
            r = hsv->v;
            g = t;
            b = p;
            break;
        case 1:
            r = q;
            g = hsv->v;
            b = p;
            break;
        case 2:
            r = p;
            g = hsv->v;
            b = t;
            break;
        case 3:
            r = p;
            g = q;
            b = hsv->v;
            break;
        case 4:
            r = t;
            g = p;
            b = hsv->v;
            break;
        case 5:
            r = hsv->v;
            g = p;
            b = q;
            break;
    }
    
    rgb->r = r;
    rgb->g = g;
    rgb->b = b;
}

void rgb2hsl(const FloatRGB *rgb, FloatHSL *hsl)
{ 
    float rd = rgb->r;
    float gd = rgb->g;
    float bd = rgb->b;
    float max = threeway_max(rd, gd, bd);
    float min = threeway_min(rd, gd, bd);
    float h, s, l = (max + min) / 2.0f;

    if (max == min) {
        h = s = 0; // achromatic
    } else {
        float d = max - min;
        s = l > 0.5f ? d / (2 - max - min) : d / (max + min);
        if (max == rd) {
            h = (gd - bd) / d + (gd < bd ? 6 : 0);
        } else if (max == gd) {
            h = (bd - rd) / d + 2;
        } else if (max == bd) {
            h = (rd - gd) / d + 4;
        }
        h /= 6;
    }
    hsl->h = h;
    hsl->s = s;
    hsl->l = l;
}



/** Convert from HSV to HSL  (this is possibly wrong) */
void hsv2hsl(const FloatHSV *hsv, FloatHSL *hsl)
{ 
    float l = (2 - hsv->s) * hsv->v / 2.0f;
    float s = hsv->s;

    if (l != 0) {
        if (l == 1) {
            s = 0;
        } else if (l < 0.5f) {
            s = s * hsv->v / (l * 2);
        } else {
            s = s * hsv->v / (2 - l * 2);
        }
    }
        
    hsl->h = hsv->h;
    hsl->s = s;
    hsl->l = l;
}

/** Convert from HSL to HSV */
void hsl2hsv(const FloatHSL *hsl, FloatHSV *hsv)
{
    float sat = hsv->s * ((hsl->l < 0.5f) ? hsl->l : (1 - hsl->l));
    hsv->s = 2*sat / (hsl->l + sat);
    hsv->h = hsl->h;
    hsv->v = hsl->l + sat;  
}


uint32_t hsl2hex(const FloatHSL *hsl)
{
    FloatRGB rgb;
    hsl2rgb(hsl, &rgb);
    return rgb2hex(&rgb);    
}

uint32_t hsv2hex(const FloatHSV *hsv)
{
    FloatRGB rgb;
    hsv2rgb(hsv, &rgb);
    return rgb2hex(&rgb); 
}


uint32_t rgb2hex(FloatRGB *rgb)
{
    return ((int)floor(rgb->r*255 + 0.5f) << 16) | ((int)floor(rgb->g*255 + 0.5f) << 8) | ((int)floor(rgb->b*255 + 0.5f));
}