Lower brightness for a given CSS hex value, used for gradients

hex_darken.rb

    # Reduces a color's brightness by a percentage
    # returns a hex value in the format "#x0x0x0"
    def self.darken(hex,percent)
      
      # convert to r,g,b 
      rgb_version = hex.to_s.gsub("#","").scan(/../).map {|color| color.to_i(16)}
      
      # reduce values by 'percent'
      new_rgb_color = rgb_version.map {|rgb| (rgb - (rgb * percent.to_f/100)).ceil}
      
      # convert back to hex 
      "#%02x%02x%02x" % new_rgb_color
    end