Which module should I use to create an OMR recognition code with Python?

I'm a beginner Wang who just finished his introduction to Python.

If students take a picture of the checked OMR card with their cell phone and send it, I would like to save it as a picture file and calculate the score through image analysis. What's the best way?

If you look at the code, you can barely understand it. I'd appreciate it if you could tell me which modules and how to approach them^{^}