int -r brightness.average (p_rgb color)          int -r brightness.hypotenuse (p_rgb color)
{                                                {
  with (color)                                     with (color)
  {                                                {
    return math:round ((->red +                      return math:round (math:sqrt ((->red ** 2 +
                        ->green +                                                   ->green ** 2 +
                        ->blue) / 3);                                               ->blue ** 2) / 3));
  }                                                }
}                                                }