OpenCV 3 Computer Vision with Python Cookbook

How to do it

You need to complete the following steps:

1. Import the necessary modules, open an input image, and copy it:

import cv2import numpy as npimg = cv2.imread('../data/circlesgrid.png', cv2.IMREAD_COLOR)show_img = np.copy(img)

2. Define two functions to implement the process of points selection :

selected_pts = []def mouse_callback(event, x, y, flags, param):    global selected_pts, show_img    if event == cv2.EVENT_LBUTTONUP:        selected_pts.append([x, y])        cv2.circle(show_img, (x, y), 10, (0, 255, 0), 3)def select_points(image, points_num):    global selected_pts    selected_pts = []        cv2.namedWindow('image')    cv2.setMouseCallback('image', mouse_callback)    while True:        cv2.imshow('image', image)        k = cv2.waitKey(1) if k == 27 or len(selected_pts) == ...