[Zope] Image management in Zope

Hi I would like to make a site, where the user can upload an image in any size. The site then have to convert the image to jpg or another optimized format. After that I would like to be able to display the picture in a form of shop-system, in different sizes. I have been looking at the Photo product, and it seems like it is close. I just can't see how I convert the image upon upload. Does anyone have some ideas regarding this. I don't mind if the solution is a commercial product to extend zope. Thank's in advance Jens Bjerre