Attached here my cython implementation of the bilateral filter, which is my first cython program. I would ask for the following: 1. Is there any way to speed up the code just by "cosmetic" modifications? 2. In particular I use the unportable gcc function __builtin_abs: Is there any way to access this in a portable way? 3. I would like to donate this code to scipy or any other suitable project. What can/should I do to realise it? Remarks: The code contains 3 end-user routines: 1. A pure python implementation: Easy to read and modify --- it can be cut out into a python source code. 2. A straight forward cython implementation: About 4 times as fast as the python implementation. 3. An optimised cython implementation earning another factor of 2 in speed (depends on the parameters used). I see this code as a "research grade" that would evolve in the near future, as I am working on a related project, and hopefully following your comments. Nadav