Lighten or darken a hexadecimal color (string)

gistfile1.rb

  # Amount should be a decimal between 0 and 1. Lower means darker
  def darken_color(hex_color, amount=0.4)
    hex_color = hex_color.gsub('#','')
    rgb = hex_color.scan(/../).map {|color| color.hex}
    rgb[0] = (rgb[0].to_i * amount).round
    rgb[1] = (rgb[1].to_i * amount).round
    rgb[2] = (rgb[2].to_i * amount).round
    "#%02x%02x%02x" % rgb
  end
  
  # Amount should be a decimal between 0 and 1. Higher means lighter
  def lighten_color(hex_color, amount=0.6)
    hex_color = hex_color.gsub('#','')
    rgb = hex_color.scan(/../).map {|color| color.hex}
    rgb[0] = [(rgb[0].to_i + 255 * amount).round, 255].min
    rgb[1] = [(rgb[1].to_i + 255 * amount).round, 255].min
    rgb[2] = [(rgb[2].to_i + 255 * amount).round, 255].min
    "#%02x%02x%02x" % rgb
  end

Pretty cool, but I prefer a more functional style, since you're doing the same operations on each value of a list

  def darken_color(hex_color, amount=0.4)
    hex_color = hex_color.gsub('#','')
    rgb = hex_color.scan(/../).map(&:hex).map{|color| color * amount}.map(&:round)
    "#%02x%02x%02x" % rgb
  end