You'd need to create a customize image selector widget to achieve this - would it be an option to simply allow users to select any image and then fix the witdh/height with image resizing instead?
See http://docs.composite.net/Configuration/Resizing-Images for info on auto resizing images. The resizing happens server side so quality and size/compression is pretty good.
Quick examples of server side image resizing:
See http://docs.composite.net/Configuration/Resizing-Images for info on auto resizing images. The resizing happens server side so quality and size/compression is pretty good.
Quick examples of server side image resizing: