If I wanted to make a picture that on the computer screen it looked like a picture of something (anything, really) but when you printed it out you could read words somehow that you could not see on the screen - how might I go about that? It's easy enough to do with a word document, but what about standard picture formats (gif, jpg or bmp)?
well, with a picture, you can make a lot more colors than a printer can. therefore, you should be able to get two really close shades of gray, and as long as you get those two colors just at the verge of where the printer would step between one color and another, you might get it. you would have to experiment to get that, and it would probably change from printer to printer.
you could stipulate that it needed to be printed on a black and white printer that would fix your problem
It has to work on any printer. In Word, as I said, it would be easy. You can designate pitures embedded into a document as screen only, print only or both. As far as I know, you can't do that with a picture. I suppose I may be able to do it with a web page - can you define a layer as non-printing? Still, I'd rather do it with an image.
