RGB_to_HWB (RGBType RGB, HWBType * HWB)
{

  /*
   * RGB are each on [0, 1]. W and B are returned on [0, 1] and H is  
   * returned on [0, 6]. Exception: H is returned UNDEFINED if W == 1 - B.  
   */

  float R = RGB.R, G = RGB.G, B = RGB.B, w, v, b, f;
  int i;

  w = MIN3 (R, G, B);
  v = MAX3 (R, G, B);
  b = 1 - v;
  if (v == w)
    RETURN_HWB (HWB_UNDEFINED, w, b);
  f = (R == w) ? G - B : ((G == w) ? B - R : R - G);
  i = (R == w) ? 3 : ((G == w) ? 5 : 1);
  RETURN_HWB (i - f / (v - w), w, b);

}
Unknown