#!ruby -Ku
# -*- mode: ruby; coding: utf-8 -*-
# Last updated: <2017/04/09 12:53:38 +0900>
#
# hls to rgb and rgb to hls
#
# License: CC0 / Public Domain

# hls to rgb, rgb to hls
module TinyColorSys

  # HLS to RGB
  # @param h [Float] hue (0.0 - 1.0)
  # @param l [Float] lightness (0.0 - 1.0)
  # @param s [Float] saturation (0.0 - 1.0)
  # @return [Array] R,G,B (0 - 255)
  def hls_to_rgb(h, l, s)
    h = (h % 1.0)
    l = [[l, 1.0].min, 0.0].max
    s = [[s, 1.0].min, 0.0].max

    if l < 0.5
      maxv = l + l * s
      minv = l - l * s
    else
      maxv = l + (1.0 - l) * s
      minv = l - (1.0 - l) * s
    end
    maxv *= 255.0
    minv *= 255.0

    h *= 360.0
    h = (h % 360.0)
    if h >= 0 and h <= 60
      r = maxv
      g = (h / 60.0) * (maxv - minv) + minv
      b = minv
    elsif h >= 60 and h <= 120
      r = ((120 - h) / 60.0) * (maxv - minv) + minv
      g = maxv
      b = minv
    elsif h >= 120 and h <= 180
      r = minv
      g = maxv
      b = ((h - 120) / 60.0) * (maxv - minv) + minv
    elsif h >= 180 and h <= 240
      r = minv
      g = ((240 - h) / 60.0) * (maxv - minv) + minv
      b = maxv
    elsif h >= 240 and h <= 300
      r = ((h - 240) / 60.0) * (maxv - minv) + minv
      g = minv
      b = maxv
    elsif h >= 300 and h <= 360
      r = maxv
      g = minv
      b = ((360 - h) / 60.0) * (maxv - minv) + minv
    end
    return r.to_i, g.to_i, b.to_i
  end

  # RGB to HLS
  # @param r [Integer] Red (0 - 255)
  # @param g [Integer] Green (0 - 255)
  # @param b [Integer] Blue (0 - 255)
  # @return [Array] hue, lightness, saturation
  #                 hue        = (0.0 - 1.0)
  #                 lightness  = (0.0 - 1.0)
  #                 saturation = (0.0 - 1.0)
  def rgb_to_hls(r, g, b)
    minv = [r, g, b].min
    maxv = [r, g, b].max

    # hue
    if maxv == minv
      h = 0.0
    else
      if r > g and r > b
        # R MAX
        h = 60.0 * (g - b) / (maxv - minv)
      elsif g > b
        # G MAX
        h = 60.0 * (b - r) / (maxv - minv) + 120.0
      elsif b > g
        # B MAX
        h = 60.0 * (r - g) / (maxv - minv) + 240.0
      else
        h = 0.0
      end
    end
    h += 360.0 if h < 0
    h /= 360.0

    # saturation
    cnt = (maxv + minv) / 2.0
    if maxv == minv
      s = 0.0
    else
      if cnt <= 127
        s = (maxv - minv).to_f / (maxv + minv)
      else
        s = (maxv - minv).to_f / (510.0 - maxv - minv)
      end
    end

    # lightness
    l = ((maxv + minv) / 2.0) / 255.0

    return h, l, s
  end
end

if $0 == __FILE__
  # ----------------------------------------
  # usage sample

  require 'dxruby'
  include TinyColorSys

  fnt = Font.new(28)
  v2 = 0.5
  set_hls = true

  Window.loop do
    break if Input.keyPush?(K_ESCAPE)

    set_hls = !set_hls if Input.mousePush?(M_LBUTTON)

    v0 = Input.mousePosX.to_f / (Window.width - 1)
    v0 = [[v0, 1.0].min, 0.0].max

    v1 = Input.mousePosY.to_f / (Window.height - 1)
    v1 = [[v1, 1.0].min, 0.0].max

    v2 += (Input.keyDown?(K_UP))? (1.0 / 255.0) : 0
    v2 -= (Input.keyDown?(K_DOWN))? (1.0 / 255.0) : 0
    v2 = [[v2, 1.0].min, 0.0].max

    if set_hls
      h = v0
      l = v1
      s = v2
      r, g, b = hls_to_rgb(h, l, s)
      h = (h * 360).to_i
      l = (l * 100).to_i
      s = (s * 100).to_i
    else
      r = (v0 * 255).to_i
      g = (v1 * 255).to_i
      b = (v2 * 255).to_i
      h, l, s = rgb_to_hls(r, g, b)
      h = (360 * h).to_i
      l = (100 * l).to_i
      s = (100 * s).to_i
    end

    Window.bgcolor = [r, g, b]
    col = (l < 50)? C_WHITE : C_BLACK
    msg = (set_hls)? "use HLS" : "use RGB"
    Window.drawFont(4, 4, msg, fnt, :color => col)
    Window.drawFont(4, 40, "RGB=#{r}, #{g}, #{b}", fnt, :color => col)
    Window.drawFont(4, 80, "HLS=#{h}, #{l}, #{s}", fnt, :color => col)
    Window.drawFont(4, 120, "(mouse x/y , Up/Down key)", fnt, :color => col)
  end

end