StegoSaurus is a free and open source tool to perform steganography on 24-bit BMP files.
Use StegoSaurus to hide and recover any type of file to and from a selected BMP image, without altering the original size of the image.
Building from source: Unarchive, open a Terminal window, go to the StegoSaurus directory in the src folder and from there run the following command:
qmake
Then double click the generated Xcode project and choose Build from the Build menu in Xcode. This will build StegoSaurus in the "/build/Debug" folder inside the source directory.