They're examples of lenticular printing , a technique undergoing a modest revival thanks to new digital-imaging capabilities.
Interlaced Images Producing a lenticular print basically takes three steps.
You create a series of images in Adobe Photoshop or any other painting program. Then you use lenticular-imaging software to cut each picture into thin vertical or horizontal slices that are interlaced to produce one image. After printing the interlaced image, you laminate it with a lenticular lens screen, a plastic covering embossed with tiny lenses set at different angles. The lenses force the eye to focus on only one of the interlaced images at any viewing angle. When you change the angle, the image changes, too.