@ahojnnes I am stuck on how to outsource this loop to Cython. I looked at the `.py` and `.pyx` files of `feature._template` and `filter._denoise` but they were different in the sense that the .py and .pyx of denoise did not have any function in common but the template ones had `match_template()` in common. It would be great if you could throw some more light on it.