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Photo Editing Software

Digital Watermark

horsegoggles
 
Posts: 70

Digital Watermark

Post Wed Jul 23, 2008 3:50 am


I don't know how many of you are interested in a way to digitally watermark your photos, but I have found a combination of open source software (free) and some self made Perl wrappers that allow you to hide as much data as you like in an image. The applications required are:

CYGWIN -Cygwin is a Linux-like environment for Windows. It consists of two parts:
A DLL (cygwin1.dll) which acts as a Linux API emulation layer providing substantial Linux API functionality.
A collection of tools which provide Linux look and feel.

PERL - Can be part of the CYGWIN install

STEGHIDE -Steghide is a steganography program that is able to hide data in various kinds of image- and audio-files. The color- respectivly sample-frequencies are not changed thus making the embedding resistant against first-order statistical tests.

SOME PERL scripts that provide a friendly interface to STEGHIDE.

I won't put any more detail in until I see if anyone is interested. It's not what I would call a simple process to set up all of this stuff, but if you are into hacking stuff, you might like this. It is free and legal.

Don

dang
 
Posts: 3780

Re: Digital Watermark

Post Wed Jul 23, 2008 5:56 am


Sounds great Don, if it's not too complicated running in Windows. If I'm understanding right, you're saying this is embedded within the image separate from the exif which would be great. Seems I'd seen a program somewhere which used a clear layer over the image to hold the data, but for some reason it wasn't available at the time, and digimark gets expensive. Sounds like this would be something a lot of people would enjoy having.

horsegoggles
 
Posts: 70

Re: Digital Watermark

Post Wed Jul 23, 2008 2:18 pm


Dang,

The data that you put in the file is password encrypted into the image file. You provide a password to encrypt the data into the image, and you use the same password to decrypt the data and it is written to a text file. The password is of your choice. To my knowledge there is no practical limit to the size of the text file you encrypt into the image

The image below has the entire first chapter of the book of Romans embeded in it, and the file size is practically the same as the original

Image

The data remains part of the image. The program Steghide is a command line program that will work in windows by itself.

If you embed text into an image, post it on a site, and later discover it on another site, submitted by someone else. Make sure to "Save picture as" using the original image name. Otherwise the encrypted data is lost. I'm no expert on this, just something I disovered.

You can download the windows version at: http://steghide.sourceforge.net/download.php.

Because I wanted to make it more user friendly and I am somewhat familiar with PERL programming language, I needed to install CYGWIN and PERL to facilitate the the use of perl in windows. More to come
Last edited by horsegoggles on Thu Jul 24, 2008 6:06 pm, edited 2 times in total.

dang
 
Posts: 3780

Re: Digital Watermark

Post Wed Jul 23, 2008 5:52 pm


Sounds great. Is it possible to have it so the file can be read without a password? Seems it would be more effective for search engines picking up the data, making tracking easier.

horsegoggles
 
Posts: 70

Re: Digital Watermark

Post Thu Jul 24, 2008 1:39 am


Dang,
I tested this out on my own photo web site which uses Serendipity to manipulate images. I wasn't able to do anything to an encrypted image to mess it up and assumed it would be the norm... mistake. I tried it out with Pbase photos and it bombed. I discovered that if I download the image with any name (like the crazy name Pbase assigns) that it would not decode. However if I save the picture with the original image name, the encrypted data is intact. Saving the picture with the crazy name and then renaming it back to the original on my computer doesn't hack it. Steghide must use the file name in the encryption process, and somehow downloading with another name messes it up. As far as your question about not using a password, I will have to try it. I was afraid for a while that Pbase was doing something in compression that messed up the data.
Don
Last edited by horsegoggles on Thu Jul 24, 2008 2:09 am, edited 1 time in total.

dang
 
Posts: 3780

Re: Digital Watermark

Post Thu Jul 24, 2008 2:03 am


Don,
Thanks for your effort. Such things are way above my head, but guess it's not surprising it wouldn't work here. Hopefully, one day, admin will release whats needed for those like you trying to write compatible programs.

horsegoggles
 
Posts: 70

Re: Digital Watermark

Post Thu Jul 24, 2008 3:41 am


Dang,
I don't think Steghide works without a passphrase.
Don

horsegoggles
 
Posts: 70

Re: Digital Watermark

Post Thu Jul 24, 2008 4:05 am


If you go to this address http://steghide.sourceforge.net/download.php, you can download the windows package. I unzipped it to a folder under c: and called it steghide.
in steghide you type steghide to get this help printout

The last two lines tell you how to encrypt data into your image and decrypt it. Emb.txt is a text file you create. Cvr.jpg is your image.

Image

dang
 
Posts: 3780

Re: Digital Watermark

Post Fri Jul 25, 2008 6:17 am


Wow... way above my head, but interesting none the less. I'll look through the full manual in the next few days to see if I can understand better. I'm trying to figure what uses I'd have for hidden text. As I'd said earlier, if it could be hidden but still read through Photoshop (as example) without being altered, it would be great for adding copyright information. But I can understand where others sharing sensitive text would find it helpful.

horsegoggles
 
Posts: 70

Re: Digital Watermark

Post Fri Jul 25, 2008 5:19 pm


Dang,

Actually the only information I intend to put in the text file that I embed in my images is copyright info.

carylwithay
 
Posts: 32

Re: Digital Watermark

Post Wed Sep 10, 2008 5:56 pm


I copied your image to see what would happen. Nothing. I can download it and copy it BUT if I go to the digimark filter I am told that this is not to be copied. Well, for those who are honest and care to check, they will find out that it is watermarked. otherwise what is the reason you do it? It does not offer real protection.
Caryl
see my gallery at: pbase.com/carylwithay

ralf
 
Posts: 311

Re: Digital Watermark

Post Thu Sep 11, 2008 2:34 am


STEGHIDE is not meant for watermarking, and is thus not robust to changes in the image; even recompressing will eradicate the hidden data, never mind cropping or resizing, since it relies on flipping low-order bits of each pixel. Programs like Digimarc use an actual watermarking algorithm which can survive some (but not all possible) modifications to an image, but can't actually store any significant amount of information -- the watermark content will usually be a 32- to 128-bit identifier (4 to 16 bytes).

dang
 
Posts: 3780

Re: Digital Watermark

Post Thu Sep 11, 2008 5:11 pm


I guess I'm still a bit confused too, since PS will actually allow adding a copyright notice into the exif, which does survive resizing as long as it's not deliberately destroyed. And since it's read by all photo programs I've checked it with, I'm not sure what's being accomplished. It's also good to note, Sheila pointed out in a thread recently, there's a free image tracking service available now which seems to work well. Google "TinEye" and you'll find it. Images can be tracked by either uploading a shot, or by url. Works great if you find a shot with lots of links to it. It's still in Beta, so they're still indexing shots at this point. But just making people aware it's there should help cut down image theft.

Am I still missing something?

horsegoggles
 
Posts: 70

Re: Digital Watermark

Post Thu Oct 16, 2008 1:18 am


I guess I jumped the gun on STEGHIDE, but it was fun while it lasted. I thought that if I could hide a bit of info in an image, and that I were to find the image in use someplace, I could download it and with STEGHIDE find the hidden information to prove it was mine. as RALF stated, it isn't robust enough. I was in hopes I had found a poor man's Digimarc.


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