Alph Tech / STUART requested a plugin to detect hidden messages in existing graphics. Using the least significan bit of color information to encode hidden messages/images is called steganography. More information can be seen at Wikipedia here: http://en.wikipedia....i/Steganography
The Idea
My first thought was to devise a code for encoding text to the least significant bit of the target image. This would have worked well, but I saw on the Wiki article that this technique could be extended to images! Cool. So, my second thought was to encode a 1 bit image (black-and-white). I played around with CodeLab until I had something workable. Then I started wondering how many bits it would take to encode a color photograph...
Once I had a working algorithm, I found Paint.NET user pleska's photo flood fill plugin source code. I started with his code and made the necessary changes. If there are any bugs in this plugin, of course, I blame pleska.
I learned a couple of new things while coding this plugin. First, stay out of other people's namespace. Heh. And, second, I learned how to put multiple plugins into a single DLL file.
The Effect DLL
If you like it, you can download the precompiled effect here:
Steganography.zip 10.91K
686 downloadsInstructions for Use
To use this plugin, you must have 2 image files. Then, follow these steps:
1. Open the graphic into which you wish to hide an image. It is best if this image has lots of detail and not much area that is a solid color.
2. Click the Effects > Steganography > Hide Image menu. You will see the following UI:
3. Click on the "..." button to select the image you wish to hide. IF you are going to pick the Black and White method, you may want to prepare your hidden image with the Floyd-Steinberg HalfTone error defusion effect.
4. Select the method (either Color or Black and White) for the encoding.
5. Click the OK button to finalize the image.
6. Save your image in a 24-bit lossless format. THIS IS CRITICAL. Lossless formats include PNG and BMP. This will not work if you save as JPG or GIF!
To view the hidden image, follow these steps:
1. Open the graphic that contains the hidden image.
2. Click the Effects > Steganography > Reveal Hidden B&W Image to view a black and white hidden image.
Or, click the Effects > Steganography > Reveal Hidden Color Image to view a color hidden image.
Sample Images
This image has a hidden Black & White image:
To view the hidden image, right click on the image
and pick "Save Image As" to save it to your computer.
Then, open the image in Paint.NET and follow the
steps above.
This image has a hidden Color image:
Enjoy 8)
P.S. More info here: <!-- m -->http://boltbait.goog...m/steganography<!-- m -->
EDITS:
Version 1.1 updated 2007-07-06: This version is not compatible with 1.0, sorry. Improved 1Bit images. Added Preview checkbox so you can see what the hidden image will look like when decoded. Compiled for release instead of debug.
-Rick Brewster
... In other words... Great Plugin!! 
