Image operations on remote server

I recently purchased a new domain for the sole purpose of hosting all the static content on a separate server and delegate CPU intensive operation like thumbnail creation on a different pool. Now I would like to do some operations on images uploaded to that remote server : creating thumbnails or updating the image if we need to. Should I download the images to my server, modify them there and then upload them back to the remote server or should I try to create web-services to manipulate the images?

One of my solution was to provide an interface to upload and manipulate the images in the new domain, by leaving the old domain when it comes time to work on im开发者_运维问答ages, but I find it kind of awkward.

I would like to keep the new domain cookie free. How would that affect my ability to restrict any random user to use the web-services if I decide to go that way?

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Well you already have a server but this seems like it would have been a good oppurtunity to use google App Engine's image API. You could upload directly (I think size limit is 1 meg) and there are functions for resize, crop, etc.

http://code.google.com/appengine/docs/python/images/overview.html