HSV to RGV conversion

hsv_to_rgv.c

void
hsv_to_rgb(double h, double s, double v, double *r, double *g, double *b):
    if (s * v == 0) {
        *r = *g = *b = v;
    } else {
        hi = ((int)(floor(3 * h / M_PI))) % 6
        f = 3 * h / M_PI - hi;
        p = v * (1.0 - s)
        q = v * (1.0 - f * s)
        t = v * (1.0 - (1.0 - f) * s)
        if (hi == 0) {
            *r = v;
            *g = t;
            *b = p;
        } else if (hi == 1) {
            *r = q;
            *g = v;
            *b = p;
        } else if (hi == 2) {
            *r = p;
            *g = v;
            *b = t;
        } else if (hi == 3) {
            *r = p;
            *g = q;
            *b = v;
        } else if (hi == 4) {
            *r = t;
            *g = p;
            *b = v;
        } else {
            *r = v;
            *g = p;
            *b = q;
        }
    }
}