OpenCV 3.x with Python By Example - Second Edition

How did we do it?

As we can see in the main function of the program, we initialize a video capture object. We then bind the function draw_rectangle with the MouseCallback function in the following line:

cv2.setMouseCallback('Webcam', draw_rectangle, event_params) 

We then start an infinite loop and start capturing the video stream. Let's see what is happening in the function draw_rectangle; whenever we draw a rectangle using the mouse, we basically have to detect three types of mouse events: mouse click, mouse movement, and mouse button release. This is exactly what we do in this function. Whenever we detect a mouse click event, we initialize the top left point of the rectangle. As we move the mouse, we select the region of interest by keeping ...