You may already know this, but pymorph is BSD licensed and may be a good starting point for incorporating morphological functions: http://luispedro.org/pymorph/ Also, I'm going to advertise the existence of this toolbox around here - I know a friend has some filtered back-projection code which may still be based on numarray, but is apparently quite fast. I'll try to get him to contribute it (and numpyify it first if necessary). Also I have some small Finite Radon Transform routines, which are pure Python and hence not super fast (but they are super fast compared to Matlab) but they do work correctly. It's not a widely used transform but if you're interested, I'm happy to contribute it to scikits.image.transform.