I know that there are a lot of free scripts to do this. However, my question is not how to do it, but how the process works. I just need some clarification, because there are many ways to do this. Do most image watermark systems add the watermark to the image, and create a temporary image that is deleted after the page is done being viewed? If this is not how the process works, how does it work, or how would it best work? Thanks! I like having an idea of how the process works before I code something, or use a script.
My guess would be the images are watermarked as they are inserted into the system then this way a page that displays 20 watermarked images doesn't have that huge over head of processing 20 images
http://www.sitepoint.com/article/watermark-images-php some powerfull functions of gd lib (http://www.boutell.com/gd/)