How to auto embed images using this plugin

This discussion is related to the HTMLPurifier addon.

Does anyone know how I can set the options of this plugin to auto embed images (restricted to a certain size) like it does with youtube videos?

I took a look at the documentation at http://htmlpurifier.org/live/configdoc/plain.html and i'm pretty sure it can be done, but I don't know exactly what I should add to the config-defaults file (this plugin is part of the V2 core)