Is there a PHP image handling class like XMLWriter for RSS or MySQLi_STMT for databases?
If you have PHP 5.3+, check out Imagine; it's quickly gaining ground to become the goto for image manipulation in PHP.
Just looked at Imagine, that seems pretty good and I'll be using it.
If you don't have PHP 5.3 then have a look at the functions here for native extensions for something lighter:
Image Processing and Generation (PHP Manual)