opencv-python: https://pypi.org/project/opencv-python/
opencv-contrib-python: https://pypi.org/project/opencv-contrib-python/
opencv-python-headless: https://pypi.org/project/opencv-python-headless/
opencv-contrib-python-headless: https://pypi.org/project/opencv-contrib-python-headless/
Added Python 3.9 support.
NOTE: Your pip version must be >= 19.3 to be able to install the pre-built manylinux2014 packages used in the latest releases. Please upgrade your pip with pip install --upgrade pip.