https://github.com/dfarmer/scikits.image/compare/master...dfarmer-filters-ca... Mostly just trying to follow procedure. I already mentioned my concerns in the previous thread. I made one stab at introduced a "None" default for the mask, but I got hung up and reverted it. The default I was going to propose was np.ones(img.shape,bool) (and after the fact I even noticed that's how it is used in one of the unit tests). But I started thinking that that could be quite wasteful of memory if you were working with large images (on my test use case with ~512x512 images it's about 300 KB for the "fake" mask). The problem I had was that if I don't allocate the emask array I get run-time errors starting at line 129 (in the diff of canny.py) because the arrays all have different lengths if they aren't logical_and'd with emask above. So anyway, I thought I would let you take a look at the code and decide if you'd like me to try to figure out a way around that or incorporate it as is (with no default) or add the np.ones default. The tests pass and as I mentioned it has worked fine so far in day-to-day use. Also regarded Ralf's comment to consolidate into one filter.py file, I agree with that I just figured I would do that with the next batch (in a separate commit). But again, let me know if I'm not approaching this properly. Thanks, Dan