How to apply a grid to an image (split the image into parts)?

Question

Python

Good afternoon!
I'm trying to apply a grid to the image (with a step of 30 pixels):

for r in range(0, img.shape[0], 30):
    for c in range(0, img.shape[1], 30):
        cv2.rectangle(img, (r, c), (r+30, c+30), (0, 0, 0), 2)

The problem is that the grid doesn't "reach" the end of the image (any).
I don't understand why is that?

(In the future, I plan to process each of the received cells in a special way, that is, plt.grid() and the like are not for this task)

Answer 1

Did you skip math at school?
Well, so as not to get up twice: