Script to create Xcode image assets

gistfile1.rb

#!/usr/bin/env ruby                                                                                                                                             
                                                                                   
require "json"                                                                     
require 'fileutils'                                                                
                                                                                   
# Requires https://github.com/JamieMason/ImageOptim-CLI                            
                                                                                   
Dir.glob("source/*.png") do |path|                                                 
  file = path.split("/").pop                                                       
  filename = file.split(".").shift                                                 
  extension = file.split(".").pop                                                  
  imageset_directory = "#{filename}.imageset"                                      
  destination = "destination/#{imageset_directory}"                                
  FileUtils.mkdir_p(destination)                                                   
                                                                                   
  contents_json = {                                                                
    images: [],                                                                    
    info: {                                                                        
      version: 1,                                                                  
      author: "Xcode"                                                              
    }                                                                              
  }                                                                                
                                                                                   
  [                                                                                
    { resize: 200, idiom: "ipad", scale: 1 },                                      
    { resize: 400, idiom: "ipad", scale: 2 },                                      
    { resize: 200, idiom: "iphone", scale: 2 },                                    
    { resize: 300, idiom: "iphone", scale: 3 },                                    
  ].each do |format|                                                               
    new_filename ="#{filename}_#{format[:idiom]}_#{format[:scale]}x.#{extension}"
                                                                                   
    # Resize each file                                                             
    `convert source/#{file} -resize #{format[:resize]}% -filter box #{destination}/#{new_filename}`
                                                                                   
    contents_json[:images] << { idiom: format[:idiom], scale: "#{format[:scale]}x", filename: new_filename }
    print "."                                                                      
  end                                                                              
                                                                                   
  # Optimize                                                                       
  #`imageOptim --directory #{destination}`                                         
                                                                                   
  File.write("#{destination}/Contents.json", contents_json.to_json)                
end