Anamorphosis is a reversible deformation of an image produced by an optical procedure (such as using a curved mirror) or through a mathematical procedure. It is a perspective effect used in art to force the observer to a certain preset or privileged point of view, from which the element takes a proportionate and clear form.
In the image we show you, a deformed image becomes an umbrella when viewed on a cone.Below you can see another anamorphosis with a snowflake. In this case a cylinder is necessary to visualize the image with its correct proportions.
You will find much more information and examples on Wikipedia.