ChunkyPNG HSV

chunky_png_hsv.rb

require 'chunky_png'

module ChunkyPNG::Color

  def h(value)
    r,g,b = r(value).to_f / MAX, g(value).to_f / MAX, b(value).to_f / MAX
    min, max = [r,g,b].minmax

    return 0 if max == min

    result = case max
      when r then (g - b) / (max - min) + (g < b ? 6 : 0)
      when g then (b - r) / (max - min) + 2
      when b then (r - g) / (max - min) + 4
    end

    result * 60
  end

  def s(value)
    min, max = [r(value), g(value), b(value)].minmax.map { |value| value.to_f / MAX }
    max == 0 ? 0 : (max - min) / max
  end

  def v(value)
    [r(value), g(value), b(value)].max.to_f / MAX
  end

  def hsv(h, s, v)
    h = h.to_f / 360
    i = (h * 6).floor
    f = h * 6 - i
    p = v * (1 - s)
    q = v * (1 - f * s)
    t = v * (1 - (1 - f) * s)

     case i % 6
      when 0 then r, g, b = v, t, p
      when 1 then r, g, b = q, v, p
      when 2 then r, g, b = p, v, t
      when 3 then r, g, b = p, q, v
      when 4 then r, g, b = t, p, v
      when 5 then r, g, b = v, p, q
    end

    rgb *[r,g,b].map {|value| (value * 255).round }
  end

end