Install OpenCV 4.1.1 on Raspberry Pi 4

The below is largely based upon this https://gist.github.com/willprice/abe456f5f74aa95d7e0bb81d5a710b60
The scripts work very well but you will need to update them to use opencv 4.1.1

I used the raspberry pi 4 with 4G of ram. It's a good idea to install heat sinks on the Pi as it will get hot during the install.

Imutils:

Once opencv is installed we need to install the imutils module. Use the command below to install it:

     sudo pip3 install imutils

Note we are doing this for python 3 thus the pip3.

ImportError: /usr/local/lib/libopencv_core.so.4.1: undefined symbol: __atomic_compare_exchange_8 Error:

If you run the test.py example and get the error above you need to edit the

/root/opencv/opencv-4.1.1/build/modules/python3/CMakeFiles/opencv_python3.dir/link.txt

file and change the first part from:

/usr/bin/c++ -fPIC -fsigned-char -W -Wall.

to

/usr/bin/c++ -fPIC  -latomic  -fsigned-char -W -Wall.

ie Add the -latomic term and then run make install again and all should be ok.