[PYTHON] Non-local means

Since m43 is said to have low sensitivity, I tried to remove noise with Non-local means (NLM).

For more information on NLM http://opencv.jp/opencv2-x-samples/non-local-means-filter

The result of removing noise with NLM from a photo of Japanese white-eye taken with Olympus E-M1. The patch is 7x7 and the search window is 21x21.

The source code is https://github.com/kibo35/restoration/blob/master/NLM/nlm.py