Optimize script with MozJPEG

optimize

#!/usr/bin/env ruby

require 'shellwords'

# Percent smaller the new file has to be to bother keeping it. The logic here
# is that in case it's already been optimized we can skip optimizing again
# given that it may have already been added to the Git repository and the new
# version will slightly different, therefore doubling up on file size.
SIZE_THRESHOLD = 0.05

#
# ---
#

CACHED_HOMEBREW_PATHS = {}
def get_homebrew_path(package)
  CACHED_HOMEBREW_PATHS[package] ||= begin
    brew_path = run_command("brew --prefix #{package}", abort: false)
    if !brew_path
      abort("Homebrew package #{package} may be unavailable; try `brew install #{package}`")
    end
    brew_path
  end
end

SIZE_ORDERS = {
  'B'  => 1024,
  'kB' => 1024 * 1024,
  'MB' => 1024 * 1024 * 1024,
  'GB' => 1024 * 1024 * 1024 * 1024,
  'TB' => 1024 * 1024 * 1024 * 1024 * 1024
}

def human_file_size(size)
  SIZE_ORDERS.each do |unit, s|
    return "#{(size.to_f / (s / 1024)).round(2)}#{unit}" if size < s
  end
end

def run_command(command, abort: true)
  ret = `#{command}`
  if $? != 0
    if abort
      abort("command failed: #{command}")
    else
      return false
    end
  end
  ret.strip
end

#
# ---
#

def main
  mozjpeg_path = if ENV["MOZJPEG_BIN"]
    File.dirname(File.dirname(ENV["MOZJPEG_BIN"]))
  else
    mozjpeg_path = get_homebrew_path("mozjpeg")

    mozjpeg_path
  end

  abort("need at least one file as argument") if ARGV.empty?
  ARGV.each do |filename|
    if File.directory?(filename)
      $stderr.puts("should not be a directory: #{filename} (skipping)") 
      next
    end

    file_ext = File.extname(filename).downcase
    if file_ext != ".jpg" && file_ext != ".jpeg"
      $stderr.puts("should be a jpg: #{filename} (skipping)")
      next
    end

    dir = File.dirname(filename)

    temp_filename = "#{dir}/#{File.basename(filename, ".*")}.temp.jpg"
    target_filename = "#{dir}/#{File.basename(filename, ".*")}.jpg"

    # DO NOT use cpjeg to pipe. It will strip EXIF.
    run_command("#{mozjpeg_path}/bin/cjpeg -outfile #{Shellwords.escape(temp_filename)} -optimize -progressive #{Shellwords.escape(filename)}")

    size = File.size(filename)
    temp_size = File.size(temp_filename)

    if temp_size < size - size * SIZE_THRESHOLD
      saved_size = size - temp_size
      saved_percent = 100 - (temp_size.to_f / size * 100).round

      # copy created/modified timestamps from the original file
      run_command("touch -r #{Shellwords.escape(filename)} #{Shellwords.escape(temp_filename)}")

      run_command("mv #{Shellwords.escape(temp_filename)} #{Shellwords.escape(target_filename)}")
      puts "created: #{target_filename} (#{human_file_size(size)} -> #{human_file_size(temp_size)} / saved #{saved_percent}%)"
    else
      run_command("rm #{Shellwords.escape(temp_filename)}")
      puts "new file within #{SIZE_THRESHOLD * 100}% of original; discarding"
    end
  end
end

#
# ---
#

main