Say you have a 1000x1000 pixel field. You can embed a dark pixel at each location to spell out something, or fractional, or even coded to a different color. There’s an immense variety of possibilities and it’s very difficult to discern even the existence of an underlying message, let alone any encryption the message itself could be in.
That is so slick! I scared myself. I actually understand what you just said. I have noticed that a bunch of my favorite tweeters have suddenly disappeared. I hope they are all on a conference call, working on this.