show images on the shell - requires imagemagick

climage.rb

#!/usr/bin/env ruby

def display_image(filename)
  tw = `tput cols`.to_i
  file = `convert #{filename} -resize #{tw}x ppm:-`.lines
  format = file.shift.chomp
  raise 'can only read binary format P6' unless format == 'P6'
  width, height = file.shift.chomp.split(' ').map(&:to_i)
  maxval = file.shift.to_i + 1
  bytes = file.join.bytes
  (0...height).each do |y|
    line = ''
    (0...width).each do |x|
      i = 3*(y*width+x)
      r = bytes[ i ] * 256 / maxval
      g = bytes[i+1] * 256 / maxval
      b = bytes[i+2] * 256 / maxval
      line << "\033[48;5;#{ 16 + 36 * (r/43) + 6 * (g/43) + (b/43) }m \033[0;00m"
    end
    puts line
  end
end

display_image ARGV[0]