As the files are being logged in a DB, the row's uniqueid/identity column will be enough. No need for any additional file processing.
But if a user or another user uploads the same pic, getting SHA1 of file will catch it since hash will match. Otherwise no way to see if files being uploaded are indentical unless you manually look at every image and see oh user12 uploaded a pic of a rabbit in this thread, and uploaded the same pic of the rabbit in another thread. This way is a user does in fact use same pic for multiple areas, or another user uploadeds same pic, the file when found to already exist will be rejected and already uploaded version will be used. So we wont have multiple copies that were just named differently by user or uploaded at a different place or time.
