README.md

cgbi_to_png

This Gem allows converting CgBI (Apple's optimized PNG) images into standard PNG images. See http://iphonedevwiki.net/index.php/CgBI_file_format

Installation

Add this line to your application's Gemfile:

gem 'cgbi_to_png'

And then execute:

$ bundle

Or install it yourself as:

$ gem install cgbi_to_png

Usage

Unoptimize single file

opng = CgBItoPNG::from_file('apple-optimized-image.png')
opng.unoptimize
opng.to_file('standard-image.png')

Unoptimized a folder of files

require 'cgbi_to_png'
require 'fileutils'
OUT_DIR = 'unoptimized_pngs'

FileUtils.mkdir_p OUT_DIR

succesfull = []
failed = {}
Dir.foreach('.') do |item|
  next unless item[/.png$/]
  begin
    opng = CgBItoPNG::from_file(item)
    opng.unoptimize if opng.optimized?
    opng.to_file(File.join(OUT_DIR, item))
    succesfull << item
  rescue Exception => e
    failed[item] = e
  end
  puts "Done"
  puts "#{succesfull.count} successful"
  puts "#{failed.count} failed"
  failed.each do |k,v|
    puts "#{k}: #{v}"
  end
end

Limitations

• Currently this Gem only supports 8bit color depth and Color Type '6' (RGB + alpha)
• Interlacing is not supported
• Alpha channel correction is not performed

Taking into account the expected usage of this Gem (viewing iOS optimized icons) these limitations are probably not a problem.

Contributing

1. Fork it ( http://github.com/jappelbe/cgbi_to_png/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request