It is well known that Google and other search engines give preference to faster sites. There are some techniques to have faster sites, but in this article, I will talk about only one: minimizing the size of your PNG files.
Having a better SEO is a must these days. The file minimization will allow your website to load faster, and as a consequence, it will rank better in the search engines.
To do this task, I write the following line:
find -name *.png | xargs optipng -o7
This line will look for all files with .png as extensions, and it will optimize utilizing the optipng tool. When this finishes, your website will have smaller files.