The Retinex algorithm, in its incarnation as McCann'99, presents an interesting mix of a locally connected iterative algorithm and a multiresolution analysis of the image. By recasting the algorithm, using wavelets, the behavior of the algorithm comes to light. This allows generalizations to be proposed, by changes in both the multiresolution structure and the iterative update structure.
Hawley K. Rising, Hawley K. Rising,
"Analysis and generalization of Retinex by recasting the algorithm in wavelets", Proc. SPIE 4662, Human Vision and Electronic Imaging VII, (30 May 2002); doi: 10.1117/12.469540; https://doi.org/10.1117/12.469540