1.从摄像头读取图片

import numpy as np
import cv2 as cv
cap = cv.VideoCapture(0)
while(True):
    # Capture frame-by-frame
    ret, frame = cap.read()  
    # Our operations on the frame come here
    gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
    # Display the resulting frame
    cv.imshow('frame',gray)
    if cv.waitKey(1) & 0xFF == ord('q'):
        break
# When everything done, release the capture
cap.release()
cv.destroyAllWindows()

2.从文件读取视频

import numpy as np
import cv2 as cv
cap = cv.VideoCapture('vtest.avi')
while(cap.isOpened()):
    ret, frame = cap.read()
    gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
    cv.imshow('frame',gray)
    if cv.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()
cv.destroyAllWindows()

3.保存视频

import numpy as np
import cv2 as cv
cap = cv.VideoCapture(0)
# Define the codec and create VideoWriter object
fourcc = cv.VideoWriter_fourcc(*'XVID')  # 保存视频的编码
out = cv.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
    ret, frame = cap.read()
    if ret==True:
        frame = cv.flip(frame,0)
        # write the flipped frame
        out.write(frame)
        cv.imshow('frame',frame)
        if cv.waitKey(1) & 0xFF == ord('q'):
            break
    else:
        break
# Release everything if job is finished
cap.release()
out.release()
cv.destroyAllWindows()