Select either "Hide image" or "Unhide image". Play with the example images (all 200x200 px) to get a feel for it.
How it works
Each channel (red, green, blue) of each pixel in an image is represented by an 8-bit value. To hide the secret image
inside the cover image, we replace the n least significant bits of the cover pixel value with the same number of most significant
bits from the secret pixel value. Example, using 3 hidden bits:
The output colour is almost indistinguishable from the cover colour, but now contains information
to extract an approximation of the secret pixel value, which gets padded with 0 to fill in the missing bits, so comes out to
(64, 192, 96) ==
(01000000, 11000000, 01100000) .
Using a larger number of hidden bits results in a better quality hidden image, but makes it easier to tell that the hidden
image is there. Play with the 'hidden bits' slider to see.
There is an example on Wikipedia of a cat hidden in a picture of a tree. To do the example here, use the 'Unhide image' tool
to select the 'Wikipedia tree' example, and set hidden bits to 2.
Once you've hidden your secret image inside a cover image, send the output image to your accomplice. Your accomplice then
uses the 'Unhide image' tool to recover the secret image.