Re: [Gimp-user] Creating Transparent WaterMark

[Ofnuts <ofnuts laposte net>]

On 04/15/2013 01:29 AM, Steve Kinney wrote:
> 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:
>
> http://www.gimpdome.com/gimp-general-use/hidden-watermarks-in-gimp/
> http://registry.gimp.org/node/21024
>
> 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.
>
> :o)
>
> Steve

For photos, the best way to demonstrate ownership it to publish a 
slightly cropped version and keep the full version for yourself (and the 
courts, if necessary)