OpenCV 3 Computer Vision with Python Cookbook

How to do it

You need to complete the following steps:

1. Import the necessary modules:

import cv2import numpy as np

2. Define a class that encapsulates mask creation:

class MaskCreator:    def __init__(self, image, mask):        self.prev_pt = None        self.image = image        self.mask = mask        self.dirty = False        self.show()        cv2.setMouseCallback('mask', self.mouse_callback)    def show(self):        cv2.imshow('mask', self.image)    def mouse_callback(self, event, x, y, flags, param):        pt = (x, y)        if event == cv2.EVENT_LBUTTONDOWN:            self.prev_pt = pt        elif event == cv2.EVENT_LBUTTONUP:            self.prev_pt = None        if self.prev_pt and flags & cv2.EVENT_FLAG_LBUTTON:            cv2.line(self.image, self.prev_pt, pt, (127,)*3, 5)            cv2.line(self.mask, self.prev_pt, pt, 255, 5)                            self.dirty = True self.prev_pt ...