[maxwell]

Here's an example of a low tech watermark:



If you had this picture open, captured the screen and then viewed the screen capture you'd still be able to see the text I printed on it, right?

This is of course a bit different from the kind of watermarks we're talking about because the modification I made is visible to the human eye. Say I kept decreasing the opacitity of the text down to 1%. You and I wouldn't be able to tell the difference between this and the original photograph, but the computer still could. This watermark will also still be able to survive the screen capture processes, since a screen capture is just a direct copy of the pixels.

This is a simplification, but hopefully it illustrates the point.

Max