scale images down to 500px and 150px width proportionally

Rakefile

desc 'scale images down to 500px and 150px width proportionally'
task :resize do
  require 'fileutils'
  Dir.chdir File.dirname(__FILE__)
  FileUtils.mkdir '500px' unless File.directory?('500px')
  FileUtils.mkdir '150px' unless File.directory?('150px')
  images = []
  (Dir['*.jpg'] - Dir['500px/**/*.jpg'].map{ |f| File.basename(f) }).each do |jpg|
    status = system("convert -resize 500x500 #{jpg} 500px/#{jpg}")
    puts "#{status ? 'Success' : 'Failed!'}: #{jpg} -> 500px/#{jpg}"
    status = system("convert -resize 150x150 500px/#{jpg} 150px/#{jpg}") if status
    puts "#{status ? 'Success' : 'Failed!'}: 500px/#{jpg} -> 150px/#{jpg}"
    images << File.realpath("500px/#{jpg}")
    images << File.realpath("150px/#{jpg}")
  end
  if images.length == 0
    puts "Nothing to do!"
  else
    system "open -a ImageOptim #{images.join(' ')}"
  end
end

desc 'finish uploading images, put them to done directory'
task :done do
  require 'fileutils'
  Dir.chdir File.dirname(__FILE__)
  %w(500px 150px).each do |width|
    FileUtils.mkdir width unless File.directory?(width)
    FileUtils.mkdir "#{width}/done" unless File.directory?("#{width}/done")
    Dir["#{width}/*.jpg"].map{ |f| File.basename(f) }.each do |file|
      FileUtils.mv "#{width}/#{file}", "#{width}/done/#{file}"
    end
  end
end