It's an old visual trick from about 20 years ago where parts of the image are print one or two pixels out of alignment - where by relaxing your eyes and not focusing on any particular part of the overall picture, an image of a house or animal emerged. There was a pile of books released on it at the time but it faded because the market got flooded. So it's just a matter of relaxing your eyes and you will find that you can flip between the two types of image. I do like the comment re only "seeing a labor government" - before the real image emerged.
