Pictures Of Inside Of The Vingina What Do You Call Those Pictures That Are Mad With Dots Which Conceal A Secret Picture Inside?

What do you call those pictures that are mad with dots which conceal a secret picture inside? - pictures of inside of the vingina

I am keen that the paintings are made in a lot of fun with the points that seem rather boring to see at first, but after a few minutes of these stars show into a hidden picture. They are hiding something like blindness tests in red color in a picture of the green dots.

If you have a link to these images on the net, I appreciate them.