Thanks Petra! 😊

Have you seen some uglier formulas? Now I'm curious.

You have definitely found the right person for scaring people with math, send them over! :D

Well, like I said to Alex above in comments - those mistakes appeared because some samples were really bad written and the algorithm by itself works nicely, but I assume that there can be some improvement.

Here's one idea - when cropping, we can after reaching first black pixels on image, to check few rows further to see do we have more black pixels - if not, we can consider it as a black spot and can continue cropping and preprocessing image. That way, we could eliminate that case of misinterpreted eight from above. I hope that I was clear :)