[rajivtiru]

I need a way to do this in Apache and/or PHP.

I think Cloudfront has a way to pass variables to your server so theoretically you can use any image generation package right?

[donavanm]

Cloudfront can vary objects by using a different uri stem, query params, or cookie contents. As noted in the article you can also route uri prefixs to your image sizer origin. So yes, I'd expect most image manipulation to be cachable using query strings for size/format/quality and a sane default for the base uri.