fly :: it depends what you need to do with the image you want to process.
I used to use gs, latex, image magick (unix version) and convert.
these programs can do whatever you can imagine really, the question is if the cpu usage has any importance to you
most of them are installed by default on redhat linux, not sure about other platforms. There is bsd 4.4 on our university server, it also had them all.
try the manual pages, i dont remember URLs really.