[nathankleyn]

Yep - that's totally possible. Actually, now you phrase it like that, I see what you mean about using it that way for a CMS, and it's an awesome idea.

[artursapek]

You could also use the canvas element to display the image & watermark as a flat layer.

[kuschku]

Still, the image would somehow have to be loaded in the browsers, at which point it’s easy to circumvent.