OpenCV 3.x with Python By Example - Second Edition

Interacting with a live video stream

Let's see how we can use the mouse to interact with a live video stream from the webcam. We can use the mouse to select a region, and then apply a negative film effect on that region, as shown in the following image:

In the following program, we will capture the video stream from the webcam, select a region of interest with the mouse, and then apply this effect:

import cv2 
import numpy as np def update_pts(params, x, y):    global x_init, y_init    params["top_left_pt"] = (min(x_init, x), min(y_init, y))    params["bottom_right_pt"] = (max(x_init, x), max(y_init, y)) img[y_init:y, x_init:x] = 255 - img[y_init:y, ...