I am writing something that needs to verify the practical readability of qr codes which has been painted over.

First thing that comes to mind is to apply Gaussian blur on the image and check if it is readable. Then I could get a “readability score” by doing binary search between blur strengths range [0, n].

I also may do the same with noise, not sure if I should.

Would appreciate if somebody with more knowledge of QR codes help me