Similarities and Differences in the Mathematical Formalizations of the Retinex Model and Its Variants

Edwin H. Land and John J. McCann introduced the Retinex model as a computational theory of color vision. However, they specified the details of Retinex rather algorithmically and not mathematically and this opened the way to a multitude of different interpretations of their model, many times even contradicting ones. The aim of this paper is to present a systematic and self-contained overview about these different interpretations and the corresponding mathematical formalizations in terms of variational principles and partial differential equations.