Pysource.com

https://pysource.com/2018/02/27/morphological-transformation-opencv-3-4-with-python-3-tutorial-17/ dilate, erode image to remove small spots. See Python and opencv#tutorials
cv2.morphologyEx dilate, erode in one step. 
=== links ===
https://github.com/navigatingbots/OpenCV-python-tests
Learnopencv.com
Pyimagesearch.com
Category:Opencv