import cv2
import math
import itertools as it

DENSITY = 5
RED = [0, 0, 255]


def draw_rectangles(frame):
    """ Draw some rectangles on top of the image """
    height, width, d = frame.shape
    n = DENSITY
    m = math.ceil(n * (height / width))
    dx = width / n
    dy = height / m
    for x, y in it.product(range(n), range(n)):
        sp = (int(x * dx), int(y * dy))
        ep = (int(x * dx + dx), int(y * dy + dy))
        frame = cv2.rectangle(frame, sp, ep, (255, 0, 0))
    return frame


if __name__ == '__main__':
    camera = cv2.VideoCapture(0)

    while True:
        ret, frame = camera.read()
        frame = draw_rectangles(frame)
        cv2.imshow('Input', frame)

        c = cv2.waitKey(1)
        if c == 27:
            break

    camera.release()
    cv2.destroyAllWindows()