These are C++ programs to hide and reveal data kept in low-order bits of lossless image files. See the video at https://www.youtube.com/watch?v=-7FBPgQDX5o
Building them requires a C++ compiler and the GraphicsMagick library. (GraphicsMagick is a variant of ImageMagick, and the latter might be made to work as well.)
On a GNU/Linux system, you can probably install the libgraphicsmagick++1-dev
package, and the equivalent of build-essential, and then type make at the
prompt.
On MacOS, I recommend using Homebrew. Once you have that, these commands should work:
brew install graphicsmagick libtool
brew link graphicsmagick libtool
make
I will happily include contributions of working build instructions for other platforms, but I cannot support them directly.
These are the programs that are available:
./encode-file input.png secret.data output.png
Encodes the secret data file into the two low-order bits of the input image, producing the output image. No guarantees if the secret data does not fit. A small change to the code determines whether it fills any remaining bits randomly, or leaves them as they were.
./decode-file input.png secret.data
Extracts the two low-order bits of each channel, writing them to the secret data file. Note: uses the entire image, so there will be some binary data left over at the end if the secrets were shorter than the original image.
./encode public.png private.png output.png
Embeds a private imagine within a public one, using 6 bits per channel from public, and 2 bits per channel from private. The result is stored in the given output filename.
./decode input.png output.png
Extracts the lowest two bits per channel from the input image, to form the output image.
./tweaky N input.png out
Specify N = the number of bits (1-7) to tweak. The output files will be named out-0s.png, out-1s.png, out-rand.png, where it tweaks the lowest N bits in the input image.
./shifty input.png out
Simulate left-shifting the channel representations, one bit at a time. The output files will be named out0.png, out1.png, etc.
./spy X Y image1.png [image2.png ...]
Identify the color of the specified X,Y coordinate in each image. Prints the color in hexadecimal and binary.