How do i add digital signatures to my photos on linux platform?

Question

I had try to use Steghide to hide a small image into my photo When i edit the resulted photos by resizing, I try to retrieve the hidden photo and it failed.

Are there possible way in which a photo with invisible watermake will still intact even when the photo is been altered?

Answer 1

You can use Gimp to add digital signature to your photos. First you should have gimp installed on your system. then install the "Digital Signature plugin" for gimp. It can be found at

http://registry.gimp.org/plugin?id=313.

If you cannot find it there search for it here

http://registry.gimp.org/list?category=9

Answer 2

If you want to add a watermark you can do it with a program written in PHP. You basically combine to images, the picture plus the image of your watermark.

There is sample code in the help system to show you how.

Doing it with PHP is cool since you can do this either sitting at the computer, or build it into a web application that does this as pictures are uploaded to your web site.