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/* hsv2rgb.c
* Integer only conversion functions between HSV and RGB
*/
#include "hsv2rgb.h"
// TODO fix these buggy macros
#define max(x,y) ((x>y) ? x:y)
#define min(x,y) ((x>y) ? y:x)
#define min3(x,y,z) (min(min(x,y),z))
#define max3(x,y,z) (max(max(x,y),z))
rgb_color hsv2rgb(hsv_color hsv)
{
// From : http://qscribble.blogspot.fr/2008/06/integer-conversion-from-hsl-to-rgb.html
int h = hsv.h;
int s = hsv.s;
int v = hsv.v;
rgb_color rgb = {0, 0, 0};
if (v == 0)
return rgb;
// sextant = 0 .. 5
int sextant = (h*6)/256;
// f = 0 .. 42
int f = h - (sextant*256)/6;
int p = (v * (256 - s))/256;
int q = (v * (256*43 - s*f))/(256*43);
int t = (v * (256*43 - s*(43-f)))/(256*43);
// Corrige les erreurs dues aux arrondis
p = max(min(p, 255), 0);
q = max(min(q, 255), 0);
t = max(min(t, 255), 0);
switch(sextant){
case 0: rgb.r = v; rgb.g = t; rgb.b = p; break;
case 1: rgb.r = q; rgb.g = v; rgb.b = p; break;
case 2: rgb.r = p; rgb.g = v; rgb.b = t; break;
case 3: rgb.r = p; rgb.g = q; rgb.b = v; break;
case 4: rgb.r = t; rgb.g = p; rgb.b = v; break;
default:rgb.r = v; rgb.g = p; rgb.b = q; break;
}
return rgb;
}
hsv_color rgb2hsv(rgb_color rgb)
{
// From : http://www.ruinelli.ch/rgb-to-hsv
hsv_color hsv = {0, 0, 0};
int min, max, delta;
min = min3(rgb.r, rgb.g, rgb.b);
max = max3(rgb.r, rgb.g, rgb.b);
if(max==0) {
hsv.h = 0;
hsv.s = 0;
hsv.v = 0;
return hsv;
}
hsv.v = max;
delta = max - min;
hsv.s = (delta)*255 / max;
if(rgb.r == max)
hsv.h = (rgb.g - rgb.b)*42/delta; // between yellow & magenta
else if(rgb.g == max)
hsv.h = 120 + (rgb.b - rgb.r)*42/delta; // between cyan & yellow
else
hsv.h = 240 + (rgb.r - rgb.g)*42/delta; // between magenta & cyan
return hsv;
}
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