OpenCV 3 Computer Vision with Python Cookbook

How to do it...

1. Import the modules:

import cv2import numpy as npimport matplotlib.pyplot as plt

2. Load the test binary image:

image = cv2.imread('../data/BnW.png', 0)

3. Find the external and internal contours. Organize them into a two-level hierarchy:

_, contours, hierarchy = cv2.findContours(image, cv2.RETR_CCOMP, cv2.CHAIN_APPROX_SIMPLE)

4. Prepare the external contour binary mask:

image_external = np.zeros(image.shape, image.dtype)for i in range(len(contours)):    if hierarchy[0][i][3] == -1:        cv2.drawContours(image_external, contours, i,         255, -1)

5. Prepare the internal contour binary mask:

image_internal = np.zeros(image.shape, image.dtype)for i in range(len(contours)):    if hierarchy[0][i][3] != -1: cv2.drawContours(image_internal, contours, ...