opencv compat

[benallard]

findContours returns only two values with opencv 4.2

[nicolashahn]

I haven't upgraded to a newer version of OpenCV because it gave me different results for some functions (possibly findContours, I don't remember exactly), changing the behavior such that it doesn't find all the sets for test_SetGame in test.py. Were you able to get this to work?

[benallard]

You're correct, it doesn't find all the cards in the pictures.

[benallard]

Actually, according to 'classify_cards_accuracy', the biggest problem it has is the shade it only got 46 out of 72. It's guessing 'solid' almost everytime. is it passing with 100% with the previous opencv ? (I cannot switch easily between the two ...)

[nicolashahn]

Results for OpenCV 3.4.2:

Score for color: 72 / 72
Score for number: 69 / 72
Score for shade: 65 / 72
Score for shape: 69 / 72
Overall accuracy: 95.48611111111111%
Perfect (full card) classifications: 60 / 72 - 83.33333333333333%

If the OpenCV version upgrade includes changes to keep or improve this level of accuracy (and pass test.py), I can accept the PR, otherwise it seems like it needs to stay at its current version.