optimize-png

#!/usr/bin/env ruby

# pngcrush -rem allb -reduce -brute original.png optimized.png
# pngcrush -d target-dir/ *.png
#
# -rem allb — remove all extraneous data (Except transparency and gamma; to remove everything except transparency, try -rem alla)
# -reduce — eliminate unused colors and reduce bit-depth (If possible)
#
# -brute — attempt all optimization methods (Requires MUCH MORE processing time and may not improve optimization by much)
#
# original.png — the name of the original (unoptimized) PNG file
# optimized.png — the name of the new, optimized PNG file
# -d target-dir/  — bulk convert into this directory "target-dir"
#
# -rem cHRM -rem sRGB -rem gAMA -rem ICC — remove color profiles by name (shortcut -rem alla)
#
# An article explaining why removing gamma correction
# http://hsivonen.iki.fi/png-gamma/

def indented_puts(str="")
  puts "  #{str}"
end

def print_manual
  script_name = "optimize-png"

  indented_puts
  indented_puts script_name
  indented_puts "=" *script_name.size
  indented_puts "- May reduce PNG file size lossless"
  indented_puts "- Removes color profiles: cHRM, sRGB, gAMA, ICC, etc."
  indented_puts "- Eliminates unused colors and reduce bit-depth (If possible)"
  indented_puts
  indented_puts "Batch optimize all *.png in current directory:"
  indented_puts "  #{script_name} output_directory"
  indented_puts
  indented_puts "Optimize single file:"
  indented_puts "  #{script_name} input.png output.png"
  indented_puts
end

def optimization_default_args
  args = ""
  args << "-rem alla " # remove everything except transparency
  args << "-rem text " # remove text chunks
  args << "-reduce " # eliminate unused colors and reduce bit-depth (If possible)
  args
end

def batch_optimize(script_args)
  output_directory = script_args[0]
  match_pattern = "*.*" # be aware of case sensitivty: *.png wouldn't match IMAGE.PNG # pngcrush does nothing with other files than png
  exec "pngcrush -d #{output_directory} #{optimization_default_args} #{match_pattern}"
end

def single_file_optimize(script_args)
  input_file = script_args[0]
  output_file = script_args[1]
  exec "pngcrush #{optimization_default_args} #{input_file} #{output_file}"
end

def main
  if ARGV.size == 1
    batch_optimize(ARGV)
  elsif ARGV.size == 2
    single_file_optimize(ARGV)
  else
    print_manual
  end
end

main