Colorify.rb

require 'miro'
require 'color'
require 'color/rgb/contrast'

Miro.options[:color_count] = 4
Miro.options[:method] = 'histogram'

class Colorify
  def get(img)
    
    base_color = nil
    final_color = nil
    hue = nil
    white = Color::RGB.new 255,255,255
    lightness_base = 70
    colors = Miro::DominantColors.new(img)
    colors_hsl = colors.to_hsl

    # Trying to exclude as many brown colors as possible
    colors_hsl.each do |c|
       base_color ||= (c[0]*360).between?(10, 50) ? nil : c
    end

    # Nothink works? no problem, let's try the second most prominent color
    base_color ||= colors_hsl[1]

    # Before committing to a particular hue, let's check if the color is too dark
    hue =  (base_color[1] < 0.1 && base_color[0] < 0.005) ? rand(0..360)/360.00 : base_color[0]

    # Now let's generate an accessible color
    lightness_base.downto(1) do |lightness|
      final_color = Color::HSL.new hue*360, 50, lightness
      break if final_color.to_rgb.contrast(white) > 0.47
    end

    return final_color.to_rgb.hex.to_s

  end
end