Having a look at Google Page Speed I liked ‘Optimize images’ section, which reports the size reduction that can be achieved in the images of a website, also offering a version of the image after having applied the reduction.

The truth is that when you save a JPG image, you don’t know exactly how much compression level apply. Sometimes we try different values until we find the best balance between quality and size. Google Page Speed must be using an algorithm that optimizes this relationship, performing a lossless compression to JPG and PNG files.

As mentioned in the section on optimization of images, we can use tools like jpegtran and jpegoptim

You can install jpegoptim in GNU / Linux easily. If you are an Ubuntu user, it is included in the section on Graphics (universe) and simply run:

sudo apt-get install jpegoptim

If you want to make the optimization of images across your website, or simply reduce the size of your photo albums, you can run this script, that will recursively scan folders to optimize every JPG file. The files will be overwritten with the optimized version.

#!/bin/bash
optimize() {
  jpegoptim *.jpg --strip-all
  for i in *
  do
    if test -d $i
    then
      cd $i
      echo $i
      optimize
      cd ..
    fi
  done
  echo
}
optimize

This script uses the option --strip-all to strip out the text information contained in the file (comments and EXIF data) that are not necessary on web images (for your own pictures you’d better keep them).