q1_1.py

import cv2
import numpy as np


def optical_flow_GF(addr):
    cap = cv2.VideoCapture(addr)
    ret, frame1 = cap.read()
    prvsImg = cv2.cvtColor(frame1, cv2.COLOR_BGR2GRAY)
    hsv_mask = np.zeros_like(frame1)
    hsv_mask[:, :, 1] = 255

    while True:
        ret, frame2 = cap.read()
        nextImg = cv2.cvtColor(frame2, cv2.COLOR_BGR2GRAY)
        flow = cv2.calcOpticalFlowFarneback(prvsImg, nextImg, None, 0.5, 3, 15, 3, 5, 1.2, 0)
        mag, ang = cv2.cartToPolar(flow[:, :, 0], flow[:, :, 1], angleInDegrees=True)
        hsv_mask[:, :, 0] = ang / 2
        hsv_mask[:, :, 2] = cv2.normalize(mag, None, 0, 255, cv2.NORM_MINMAX)
        bgr = cv2.cvtColor(hsv_mask, cv2.COLOR_HSV2BGR)
        cv2.imshow('frame2', bgr)
        k = cv2.waitKey(10) & 0xff

        if k == 27:
            break
        prvsImg = nextImg

    cap.release()
    cv2.destroyAllWindows()

if __name__ == '__main__':
    optical_flow_GF('cars.mp4')