Filerobot can place a watermark on top of your images if you want to protect them from copying, or tag them with a serial number or custom text. There are three types of watermarks - click on each one for more details.
In the above fragment, wat_opacity=0.5 will be applied to both watermarks.
Multiple watermark types
Combining multiple watermark types is also possible. Remember that the presense of wat_url=X parameter defines a dynamic watermark, wat_text=X defines a text watermark and the absence of either defines a static watermark.