Slice up a photo of a dog and reassemble it, and you’ll be left with two images of the same pup. Slice those photos up again, and somehow you’ll then have four images of that doggo. It seems like an impossible optical illusion, but this neat trick is actually a very basic demonstration of how image editing apps work.
To be fair to a complicated application like Photoshop, Kensuke Koike’s fun video is a gross simplification of how a digitised image is reduced in size. Complex algorithms are used to ensure that when a pixelated image is shrunk, the results are sharp while lines and edges remain smooth.
But slicing this real-life dog photo both vertically and horizontally essentially turned it into a compilation of smaller pixels. And when you throw away every other pixel in an image, the results are half as large as the original, but still completely recognisable, if the pixels are small enough.