【01】Dense Optical Flow in OpenCV (Python) Optical Flow Video

B station operation video: https://www.bilibili.com/video/BV14V4y1V7mT/

Dense Optical Flow in OpenCV

import numpy as np
import cv2


cap = cv2.VideoCapture('./1.mp4')

#获取第一帧
ret, frame1 = cap.read()
prvs = cv2.cvtColor(frame1,cv2.COLOR_BGR2GRAY)
hsv = np.zeros_like(frame1)

#遍历每一行的第1列
hsv[...,1] = 255


while(1):
    ret, frame2 = cap.read()
    next = cv2.cvtColor(frame2,cv2.COLOR_BGR2GRAY)

    #返回一个两通道的光流向量，实际上是每个点的像素位移值
    flow = cv2.calcOpticalFlowFarneback(prvs,next, None, 0.5, 3, 15, 3, 5, 1.2, 0)

    #print(flow.shape)
    print(flow)

    #笛卡尔坐标转换为极坐标，获得极轴和极角
    mag, ang = cv2.cartToPolar(flow[...,0], flow[...,1])
    hsv[...,0] = ang*180/np.pi/2
    hsv[...,2] = cv2.normalize(mag,None,0,255,cv2.NORM_MINMAX)
    rgb = cv2.cvtColor(hsv,cv2.COLOR_HSV2BGR)

    cv2.imshow('frame2',rgb)
    k = cv2.waitKey(30) & 0xff
    if k == 27:
        break
    elif k == ord('s'):
        cv2.imwrite('opticalfb.png',frame2)
        cv2.imwrite('opticalhsv.png',rgb)
    prvs = next

cap.release()
cv2.destroyAllWindows()

python demo.py

refer to

Optical Flow in OpenCV (C++/Python)：https://learnopencv.com/optical-flow-in-opencv/

Optical Flow：https://docs.opencv.org/4.x/d4/dee/tutorial_optical_flow.html

Python opencv entry optical flow method (41): https://blog.csdn.net/tengfei461807914/article/details/80978947