I just finished implementing an image processing service with a URL-based API

I wrote a PHP script along a similar line.

Example:

http://fritzw.com/resizer.php?w=80&h=30&c=0&f=ht...

Code:

http://fritzw.com/Programming/do/resize

Doesn't have as many options but great for developers who don't want to open PS every time a client hands you a new photo to throw on the site.

Interesting idea for a service. I wrote an Apache module that is very similar.

http://code.google.com/p/moddims/