getRainbow.c

#include <stdio.h>
#include "rainbow.h"

void HSVtoRGB(float *r, float *g, float *b, float h, float s, float v)
{
    int i;
    float f, p, q, t;
    if (s == 0) {
        *r = *g = *b = v;
        return;
    }
    h /= 60;
    i = h;
    f = h - i;
    p = v * (1 - s);
    q = v * (1 - s * f);
    t = v * (1 - s * (1 - f));

    switch (i) {
        case 0:
            *r = v;
            *g = t;
            *b = p;
            break;
        case 1:
            *r = q;
            *g = v;
            *b = p;
            break;
        case 2:
            *r = p;
            *g = v;
            *b = t;
            break;
        case 3:
            *r = p;
            *g = q;
            *b = v;
            break;
        case 4:
            *r = t;
            *g = p;
            *b = v;
            break;
        default:
            *r = v;
            *g = p;
            *b = q;
            break;
    }
}