So many questions already about this topic, but I didn\'t find any satisfying answer about the \"DLL not found\" traditional issue.
As mentioned in the comment which I didn't notice at first, you can resolve this by installing from the unofficial site (Gohlke) (http://www.lfd.uci.edu/~gohlke/pythonlibs/#opencv)
I uninstalled the official one by calling:
pip uninstall opencv-python
And then downloaded the .whl package from the mentioned site (you need to carefully choose the correct python version and the correct processor architecture x86 or x64).
And then, go to the path where the .whl file is downloaded and call:
pip install opencv_python-x.x.x-cpxx-cpxxm-win_xx.whl