How to use phpthumb snippet inside a module (or how to make a thumbnail)

I am coding a module for newsletter and I need a way to make a thumbnail with border and rounded corners from a image in a template variable and save it on the server so I can get an absolute url to the thumbnail since it is going to be in an email. I usually use phpthumb to do this, but that is in chunks and snippets.

How can I call phpthumb to make a thumbnail from inside the module?

It seems that I’ve a problem quite similar : I would like to use the phpthumb in the core like this :

<img id="PhotoMembre" src="connectors/system/phpthumb.php?w=110&src=[[getResourceField? &id=`[[*createdby:userinfo=`phone`]]` &isTV=`1` &field=`ImageTV`]]" title="" alt=""/>

To help you understand this line of code : each membre has a resource with an image field (and many other informations, like a full profile. In the classical user profile, the field "phone" is used to put the ID of member’s ressource. I can’t use a filter output because the image name come from a getResourceField call.

This code was perfectly working before MODx 2.0.8 . Since this release (the same for 2.1RC4), it shows a blank picture.

The other solution I see is to transform phpthumb output filter as a snippet?

Any other idea?

Many thanks in advance