Archived posting to the Leica Users Group, 1999/02/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Dear David, Can you, or someone who is familiar with the technology, please explain how these digital "watermarks" work? Curuious. Thanks, Joe Stephenson - -----Original Message----- From: David Morton <dmorton@journalist.co.uk> To: leica-users@mejac.palo-alto.ca.us <leica-users@mejac.palo-alto.ca.us> Cc: dmorton@journalist.co.uk <dmorton@journalist.co.uk> Date: Tuesday, February 09, 1999 5:28 PM Subject: Re: [Leica] Web publishing and watermarks >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 >invisible. > >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 >dmorton@journalist.co.uk | longer obey their parents and >David.Morton@openconsulting.co.uk | 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 >idea > > >