Over the years I have written quite a lot of Matlab code. The code is available here, here, here, and here and covers mostly image processing and interpolation/approximation topics. All the code is released under a GPL v3 licence (unless specified differently).
Note: This code has been rotting on my computers for years now. It’s badly documented, likely to be buggy and probably won’t even run without some fixes. I don’t have access to Matlab any longer and have no plans in using this code any more.