UNM Scheme is an implementation of the Scheme programming language written by yours truly to serve as the interface for an image processing library. Unlike vanilla Scheme, it contains primitive types for representing real and complex images; expressions which evaluate to either type cause a window to be created and the image to be displayed automatically. Additionally, as in MATLAB, all arithmetic functions are overloaded and work on any combination of real or complex images and scalars.
UNM Scheme is a fairly complete implementation of Scheme except that all numbers are represented internally as floats, i.e., there is no support for rationals or bignums. It has characters, strings, vectors, and quasiquote. It has call/cc and define-macro but not define-syntax.