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Invisible Watermark? Where And What?  
User currently offlineBlackened From , joined Dec 1969, posts, RR:
Posted (14 years 10 months 4 weeks 10 hours ago) and read 3009 times:

The photo usage page of this site says all pictures carry an invisible watermark. Where is it and what is it? How can you see it?

3 replies: All unread, jump to last
User currently offlineMikephotos From United States of America, joined Oct 2000, 2923 posts, RR: 52
Reply 1, posted (14 years 10 months 4 weeks 10 hours ago) and read 2978 times:

If it's invisible, I don't think you can see it  Smile

Seriously, I'd be curious to know myself.....


User currently offlineShamrock77 From , joined Dec 1969, posts, RR:
Reply 2, posted (14 years 10 months 4 weeks 8 hours ago) and read 2965 times:

Hey ,
I could be way off here, in fact I probably am, but as far as I know there is a way of embedding text in the .jpg file.

Perhaps this is how it is done, maybe not, but it's something to think about!

It was used in the movie 'Along Came A Spider'
The rich kids in the movie used this method to pass notes around the class,
no-one knew what they were doing, cause it seemed as if they were just sharing pictures.

Don't blame me if I'm totally wrong!!


User currently offlineJwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 17
Reply 3, posted (14 years 10 months 3 weeks 4 days 12 hours ago) and read 2916 times:

There is a way to add extra headers to a JPEG file that can contain just about anything. A good program that does not recognise these headers should leave them in place (a bad program may remove them...).

From a document on the JPG format:
"APP0 marker used for application-specific information

Additional APP0 marker segments can be used to hold application-specific information
which does not affect the decodability or displayability of the JFIF file. Application-
specific APP0 marker segments must appear after the JFIF APP0 and any JFXX APP0
segments. Decoders should skip any unrecognized application-specific APP0 segments.

Application-specific APP0 marker segments are identified by a zero terminated string
which identifies the application (not "JFIF" or "JFXX"). This string should be an
organization name or company trademark. Generic strings such as dog, cat, tree, etc.
should not be used. "

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