rgb.cpp

#include "rgb.hpp"

struct rgb hsv_to_rgb(struct hsv hsv)
{
  struct rgb rgb;
  unsigned char region, remainder, p, q, t;

  if (hsv.s == 0) {
    rgb.r = hsv.v;
    rgb.g = hsv.v;
    rgb.b = hsv.v;
    return rgb;
  }

  region = hsv.h / 43;
  remainder = (hsv.h - (region * 43)) * 6;

  p = (hsv.v * (255 - hsv.s)) >> 8;
  q = (hsv.v * (255 - ((hsv.s * remainder) >> 8))) >> 8;
  t = (hsv.v * (255 - ((hsv.s * (255 - remainder)) >> 8))) >> 8;

  switch (region) {
  case 0:  rgb.r = hsv.v; rgb.g = t;     rgb.b = p;     break;
  case 1:  rgb.r = q;     rgb.g = hsv.v; rgb.b = p;     break;
  case 2:  rgb.r = p;     rgb.g = hsv.v; rgb.b = t;     break;
  case 3:  rgb.r = p;     rgb.g = q;     rgb.b = hsv.v; break;
  case 4:  rgb.r = t;     rgb.g = p;     rgb.b = hsv.v; break;
  default: rgb.r = hsv.v; rgb.g = p;     rgb.b = q;     break;
  }

  return rgb;
}