Archived posting to the Leica Users Group, 1999/02/09

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Subject: Re: [Leica] Web publishing and watermarks
From: (David Morton)
Date: Tue, 9 Feb 1999 20:25 +0000 (GMT Standard Time)

Pascal wrote:
> There is one such scheme built-in into Adobe Photoshop 5 (at least in 
> the Mac version), Digimarc. It is quite simple and the basic functions 
> are for free.
> However, I have the impression that such watermarks can deteriorate 
> image quality (more "pixelisation" and loss of sharpness).

If it's correctly implemented it certainly *shouldn't* be visible at all. 
With the right choice of spreading function it's possible to conceal the 
watermark below the noise floor of the image, making it effectively 

For example, every BBC programme has been watermarked since the early 
nineteen eighties (*), and I don't think anyone's noticed yet!

David Morton                       |  "Times are bad. Children no           |  longer obey their parents and  |  everyone is writing a book."
(+44) 171 917 6272                 |  Marcus Tullius Cicero (106-43 BC)

(*) and some of these young techies would have you believe this is a new