Currently I am working on a visual cryptography tool named Nemesis. Nemesis will be available for free and it will be published under a Creative commons licence. The screenshot below shows an alpha version GUI to test the model layer. It could differ from a later version I'll publish. The software bases on the work of Naor & Shamir (1994)1. In its very first version it only extracts the colored part of an source image to generate a black output as you can see below.
Visual Cryptography is an astonishing easy to understand and easy to use technique to encrypt images by computing a key and an encrypted image.
If one print the key on a translucent foil and the encrypted image on a normal sheet and stack both together the black amount of the source image appears as it was.
You can watch the effect on the fourth image of the screenshot.
Mathematically spoken VC is a sort of one-time pad and therefore can't be broken. Given that the key image is used only one single time for encryption. With Nemesis it is only a click to produce multiple key images with a given size. So Alice will be able to give a huge bunch of keys to Bob in one go for later use.