On 04/14/2013 12:19 PM, WanderingPen wrote:

> I would like to add a hidden watermark to my photos, but not sure how to do 
> so.
> I did find a tutorial of how to make the watermark in GIMP, but it was written
> using an old version of GIMP. I have the current 2.8 version.

Transparent vs. Hidden is a potential question.  We often see
"transparent" watermarks on commercial clip art, typically a mosaic
of copyright notices positioned to "ruin" the image while allowing
the original to show through.  This is easily done via a text or
image layer with its transparency adjusted.

To create a "really" hidden watermark with the GIMP, see this
tutorial, and a plugin using the same method:


Not sure about the plugin, but the tutorial should work on any
recent version of the GIMP.  I just tested it in GIMP 2.8 and it
worked as advertised.

The plus side:  This kind of watermark is very hard to spot, and
difficult to remove even if someone realizes that it is present.

The minus side:  Digging a hidden watermark back out of a marked
image and reading it, requires a copy of both the original and the
watermarked image, and involves doing operations to reveal the
difference between the marked and unmarked versions.  You may need
to hire an expert witness if you need to introduce this kind of
watermark into evidence in a Court proceeding, to do the watermark
extraction and render an "opinion" that it is genuine.

By the time all is said and done, maybe it would be better to e-mail
a copy of the original to yourself via a webmail service.  A printed
copy of this message provides a 3rd party time stamp, for proof of
priority of publication.  For a large number of images, e-mailing
MD5 or SHA checksums of your original files to yourself may be a
more practicable method of getting a 3rd party time stamp.



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