optimize.rake

desc "Optimize GIF, JPG and PNG files"
task :optimize => [ 'optimize:find_tools', 'optimize:run' ]

namespace :optimize do
  desc "Test for presence of image optimization tools in the command path"
  task :find_tools do
    RakeFileUtils.verbose(false)
    tools = %w[jpegtran gifsicle pngcrush]
    puts "\nOptimizing images using the following tools:"
    tools.delete_if { |tool| sh('which', tool) rescue false }
    raise "The following tools must be installed and accessible from the execution path: #{ tools.join(', ') }" if tools.size > 0
  end

  task :run do
    RakeFileUtils.verbose(false)
    start_time = Time.now

    file_list = FileList.new 'public/images/**/*.{gif,jpeg,jpg,png}'

    last_optimized_path = 'public/images/.last_optimized'
    if File.exists? last_optimized_path
      last_optimized = File.new last_optimized_path
      file_list.exclude do |f|
        File.new(f).mtime < last_optimized.mtime
      end
    end

    puts "\nOptimizing #{ file_list.size } image files."

    proc_cnt = 0
    skip_cnt = 0
    savings = {:old => Array.new, :new => Array.new}

    file_list.each_with_index do |f, cnt|
      puts "Processing: #{cnt+1}/#{file_list.size} #{f.to_s}"

      extension = File.extname(f).delete('.').gsub(/jpeg/,'jpg')
      ext_check = `file -b #{f} | awk '{print $1}'`.strip.downcase
      ext_check.gsub!(/jpeg/,'jpg')
      if ext_check != extension
        puts "\t#{f.to_s} is a: '#{ext_check}' not: '#{extension}' ..skipping"
        skip_cnt = skip_cnt + 1
        next
      end

      case extension
      when 'gif'
        `gifsicle -O2 #{f} > #{f}.n`
      when 'png'
        `pngcrush -q -rem alla -reduce -brute #{f} #{f}.n`
      when 'jpg'
        `jpegtran -copy none -optimize -perfect -progressive #{f} > #{f}.p`
        prog_size = File.size?("#{f}.p")

        `jpegtran -copy none -optimize -perfect #{f} > #{f}.np`
        nonprog_size = File.size?("#{f}.np")

        if prog_size < nonprog_size
          File.delete("#{f}.np")
          File.rename("#{f}.p", "#{f}.n")
        else
          File.delete("#{f}.p")
          File.rename("#{f}.np", "#{f}.n")
        end
      else
        skip_cnt = skip_cnt + 1
        next
      end

      old_size = File.size?(f).to_f
      new_size = File.size?("#{f}.n").to_f

      if new_size < old_size
        File.delete(f)
        File.rename("#{f}.n", f)
      else
        new_size = old_size
        File.delete("#{f}.n")
      end

      savings[:old] << old_size
      savings[:new] << new_size

      reduction = 100.0 - (new_size/old_size*100.0)

      puts "Output: #{sprintf "%0.2f", reduction}% | #{old_size.to_i} -> #{new_size.to_i}"
      proc_cnt = proc_cnt + 1
    end

    total_old = savings[:old].inject(0){|sum,item| sum + item}
    total_new = savings[:new].inject(0){|sum,item| sum + item}
    total_reduction = total_old > 0 ? (100.0 - (total_new/total_old*100.0)) : 0

    minutes, seconds = (Time.now - start_time).divmod 60
    puts "\nTotal run time: #{minutes}m #{seconds.round}s"

    puts "Files: #{file_list.size}\tProcessed: #{proc_cnt}\tSkipped: #{skip_cnt}"
    puts "\nTotal savings:\t#{sprintf "%0.2f", total_reduction}% | #{total_old.to_i} -> #{total_new.to_i} (#{total_old.to_i - total_new.to_i})"

    FileUtils.touch last_optimized_path
  end
end