OpenCV 3 Computer Vision with Python Cookbook

How to do it...

1. Import all of the necessary modules, open an image, and display it on the screen:

import cv2, randomimport numpy as npimg = cv2.imread('bw.png', cv2.IMREAD_GRAYSCALE)

2. Find the contours of the loaded image, draw them, and show the result:

im2, contours, hierarchy = cv2.findContours(img, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)color = cv2.cvtColor(img, cv2.COLOR_GRAY2BGR)cv2.drawContours(color, contours, -1, (0,255,0), 3)cv2.imshow('contours', color)cv2.waitKey()cv2.destroyAllWindows()

3. Take the first contour, find its area in various cases, and output the resulting numbers:

contour = contours[0]print('Area of contour is %.2f' % cv2.contourArea(contour))print('Signed area of contour is %.2f' % cv2.contourArea(contour, True)) ...