ansi 256 color swatch sample in ruby

gistfile1.rb

#!/usr/bin/env ruby
#
# Usage: 256swatch [-b [foreground [test pattern]]]
#
#       option              description                default
#    -----------------------------------------------------------
#
#              -b    print background swatches instead  normal
#
#      foreground    force foreground (decimal)         normal
#
#    test pattern    text to display                    'test'

def swatch(s, width=16)
  def foreground(x) ; "\033[38;5;#{x}m" end
  def background(x) ; "\033[48;5;#{x}m" end
  def reset         ; "\033[0m"         end

  result = '    ' + (0...width).map{|x|sprintf "%*d",s.size-1+(x==0?0:2),x}.join + "\n"  # header
  color  = 0
  begin #   row header              each cell                    color     cell reset  btw_cell  eol
    result += sprintf("%3d ",color)+(0...width).collect{yield(color+=1).to_s+s+reset}.join(' ')+"\n"
  end until color == 256
  result
end


puts <<-eos

#{swatch(ARGV[2]||"test") { |x| (ARGV[0] ? background(x) : foreground(x)) +
                                (ARGV[1] ? foreground(ARGV[1].to_i) : '') }}

eos