wtf.rb

wtf.rb

def rgb_to_hsv(r, g, b)
  if r == b && r == g
    h = s = 0
    v = (0.299 * r + 0.587 * g + 0.114 * b) / 255
  else
    max = [r, g, b].max.to_f
    min = [r, g, b].min.to_f

    v = max
    s = min

    if max == r
      if min == b
        h = g
        fi = Proc.new { |a| -1 == a ? 0 : 120 - 2 * (120 * Math.atan(a/0.5)/Math::PI) }
      else
        h = b
        fi = Proc.new { |a| -1 == a ? 0 : 315 + 2 * (45 *  Math.atan(a/1.33)/Math::PI) }
      end
    elsif max == g
      if min == r
        h = b
        fi = Proc.new { |a| -1 == a ? 180 : 210 - 2 * (30 * Math.atan(a/0.75)/Math::PI) }
      else
        h = r
        fi = Proc.new { |a| -1 == a ? 180 : 120 + 2 * (60 * Math.atan(a/0.5)/Math::PI) }
      end
    else
      if min == r
        h = g
        fi = Proc.new { |a| -1 == a ? 255 : 210 + 2 * (45 * Math.atan(a/1.33)/Math::PI) }
      else
        h = r
        fi = Proc.new { |a| -1 == a ? 255 : 315 - 2 * (60 * Math.atan(a/1.33)/Math::PI) }
      end
    end

    if h == min
      temp = -1
    else
      temp = (max-h)/(h-min)
    end
    h = fi.call(temp)

    s = (v-s)/v
    v /= 255
  end

  return [h, s, v]
end

def hsv_to_rgb(h, s, v)
  max = v * 255
  min = max - s * max

  fi = case h
  when (0.0..120.0)
    Proc.new { |a|   0 == a ? -1 : 0.5  * Math.tan((120 - a)/120 * Math::PI / 2) }
  when (120.0..180.0)
    Proc.new { |a| 180 == a ? -1 : 0.5  * Math.tan((a - 120)/60 *  Math::PI / 2) }
  when (180.0..210.0)
    Proc.new { |a| 180 == a ? -1 : 0.75 * Math.tan((210 - a)/30 *  Math::PI / 2) }
  when (210.0..255.0)
    Proc.new { |a| 255 == a ? -1 : 1.33 * Math.tan((a - 210)/45 *  Math::PI / 2) }
  when (255.0..315.0)
    Proc.new { |a| 255 == a ? -1 : 1.33 * Math.tan((315 - a)/60 *  Math::PI / 2) }
  when (315.0..360.0)
    Proc.new { |a|   0 == a ? -1 : 1.33 * Math.tan((a - 315)/45 *  Math::PI / 2) }
  else
    raise ArgumentError
  end

  tmp = fi.call(h)
  tmp = (tmp == -1) ? min : (max + tmp*min) / (tmp + 1)

  case h
  when (0.0..120.0)
    return [max, tmp, min]
  when (120.0..180.0)
    return [tmp, max, min]
  when (180.0..210.0)
    return [min, max, tmp]
  when (210.0..255.0)
    return [min, tmp, max]
  when (255.0..315.0)
    return [tmp, min, max]
  when (315.0..360.0)
    return [max, min, tmp]
  else
    raise ArgumentError
  end
end

p rgb_to_hsv(0x2B, 0x00, 0xFF)
p hsv_to_rgb(225, 1.0, 1.0)