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Steganography (version 3.0 Updated 2014-07-12) 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.org/wiki/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. EDIT: I completely rewrote the UI for v2.0 of this plugin. It is now for Paint.NET 4.0+ only. Also, I broke out the encode and decode effects to separate files. Only crazy people put more than one effect in a single dll file. The Effect DLL If you like it, you can download the precompiled effect here: Steganography30.zip Instructions 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. Somewhat darker images seem to work best. 2. Click the Effects > Steganography > ...Encode From File... You will see the following UI: 3. Click on the "Browse" button and select the image you wish to hide. You will see a loading bar while the image loads. This can take some time for large images. 4. Check the "Preview decoded image" check box. This will allow you to see the hidden image while you adjust the various controls. 5. Select the method (either Color or Black and White) for the encoding. 6. Adjust the various controls. When you are happy with how the decoded image will look, UNcheck the "Preview decoded image" check box. 7. Click the OK button to finalize the image. 8. 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 1. Open the graphic that contains the hidden image. 2. Click the Effects > Steganography > B&W Decoder to view a black and white hidden image. Or, click the Effects > Steganography > Color Decoder to view a color hidden image. Note: There's no way of knowing if a color image, a b&w image, or no image is hidden before running the decoder. Just try one and if it doesn't work just press Ctrl-Z to get back your original. 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) 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. Version 2.0 updated 2014-07-09: Compiled for Paint.NET 4.0. Algorithm is the same, only the UI has changed. Version 3.0 updated 2014-07-12: Added Floyd-Steinberg dithering to hidden image. This dramatically improves the quality of the hidden image.