mod_pagespeed image compression with primefaces

Question

Why does mod_pagespeed compress images rendered using <h:graphicImage> but not images using <img>.

For example: Doesn't get compressed:

<img src="/resources/img/logo.png" alt="Logo" height="50" width="230" />

This does get compressed:

<h:graphicImage library="img" name="logo.png" alt="Logo"  height="50" width="230" />

Answer 1

mod_pagespeed will only compress cacheable images:

https://developers.google.com/speed/pagespeed/module/faq#not-rewriting