Anytime I need to do any server side manipulation of images I start off thinking “OK, let’s just use GD. It’s built into PHP and I won’t have to muck about with perl, or worse, with PerlMagick.
This goes fine until I need to do something with an alpha channel and GD starts acting completely screwy, which prompts me to swallow hard to dive into the “incredibly poorly documented but will eventually work as advertised” ImageMagick.