Images and MySQL - please help

Hi, I am trying to do this: - I have an image stored in database 'A' - a php script should load this image, and "stamp" it with a watermark - then the php script should save the new image (with the watermark) in database 'B' ... How can I do this? I guess somehow I have to buffer the output, manipulate the buffer by adding the watermark, and then "insert" the image into the database. Is this possible? Any ideas? Thanks! DrTebi