Originally Posted by Chio

Take a look at gallery 2 watermark code. It does that.

Example:

It should have skarkyfarts logo on the bottom.

Now click the link below and refresh to see the non hotlink version.

http://www.sharkyfarts.com/gallery/v...etski.jpg.html

EDIT: You can set different watermark files as well depending on what's happening... viewed on site, hotlinked, etc.