Distance maps can be calculated using the OpenCV cv2.distanceTransform function. It calculates the specified type of distance (cv2.DIST_L1, cv2.DIST_L2, or cv2.DIST_C) to the closest zero pixel. You can also vary the mask size that's used for computing the approximate distance (the available options are cv2.DIST_MASK_3 and cv2.DIST_MASK_5). You can also use the cv2.DIST_MASK_PRECISE flag, which leads to computing not approximate, but precise distances.
The following output is expected:
