Anamorphic:
Anamorphic describes a projection or drawing that is distorted, though when observed through a particular viewpoint or method, it appears normal. For instance, some artists draw, paint or print a flat image which appears to be distorted in shape and perspective, but when its reflection is viewed in a cylindrical mirror, it appears normal. Another example involves the anamorphic lens, a type of film lens that stretches the image into a wider, higher quality image. Originally, anamorphic was a geological term describing certain types of metamorphic rock. The word anamorphic is derived from the Greek word anamorphōsis which means transformation. [Grammarist]
Noted in “Christmas crafts: How to make your own amazing optical illusion,” Daniel Cossins, NewScientist (19 December 2020):
Anamorphic illusions, from the Greek word for “transformation”, have been popular since at least the Renaissance, when artists like Leonardo da Vinci were experimenting with perspective. Perhaps the most famous example is a 16th-century painting called The Ambassadors by Hans Holbein the Younger, in which a distorted shape at the bottom of the picture is revealed to be a skull when viewed from an acute angle.
It also includes instructions on how to do your own anamorphic illusion.
