Back in the years when I was still coding in QBASIC (pretty nice language to start programmation), I took an interest in steganography (see Wikipedia for more information on the subject) and quickly came across an article describing a technique to hide a picture into another one . The aim of this post is to share this technique and rapidly shows how it can be implemented in HTML5 using canvas elements. The original piece of software I built with QBASIC, I called it "Blackshell", did work neatly, but was very slow (about 1 min of processing to hide a 100*100 picture). As I've been looking for a project to get myself started with the use of canvases with HTML5 for a few months, I thought I might just try to port that tool in HTML/JS. You can find a first draft here: http://manuthommes.be/toolbox/html5exp/ EDIT: it seems that the script does not run properly on my website any longer (beats me why...). If you encounter trouble too (i.e. the colors are all weird...