There are many more things we can do with image files. One thing we can do is use steganography to conceal messages inside image files. As image files are large, complex, and relatively noisy, adding a few extra bits of data won't make much of a visible change to the image or the file.

Sometimes this is summarized as adding a digital watermark to an image. We're going to subtly alter the image in a way that we can recognize and recover it later.

Adding a message can be seen as a lossy modification to the image. Some of the original pixels will be unrecoverable. As the JPEG compression, in general, already involves minor losses, tweaking the image as part of steganography will be a similar level of image corruption.

Speaking of losses, the JPEG format can, and will, tweak some of the bits in our image. Consequently, it's difficult to perform steganography with JPEG. Rather than wrestle with JPEG details, we'll use the TIFF format for our concealed messages.

There...