Alright, take a look at the two versions of Starry Night above. They look the same, right?
There’s a Shel Silverstein poem in one of them. It’s chilling out in the different red values of the pixels in the upper left hand corner on the second Starry Night. I love this method of hiding messages.
If you convert letters into numbers, you can use those to make pixel color changes that are pretty darn subtle. Then when you send your encoded image to anyone with the original, they can use Processing to pull the message out.