USB Camera

#  -*- coding: UTF-8 -*-
import cv2  # Import OpenCV library


# Open usb camera 0.
cap = cv2.VideoCapture(0) 
# Set the camera buffer to 1, to decrease the latency.
cap.set(cv2.CAP_PROP_BUFFERSIZE, 1) 
# Set the windows to be full screen.
cv2.namedWindow('winname',cv2.WND_PROP_FULLSCREEN) 
# Set the windows to be full screen.
cv2.setWindowProperty('winname',cv2.WND_PROP_FULLSCREEN, cv2.WINDOW_FULLSCREEN) 

index = 1
fourcc = cv2.VideoWriter_fourcc(*'mp4v')

while (cap.isOpened()): 
    # Read one frame from usbcam.
    ret, frame = cap.read() 
    # If frame available. 
    if ret: 
        '''crop the center of the frame and resize to (240, 320) while keeping image ratio.'''
        h, w, c = frame.shape  # Record the shape and size of the image, including height, width, and channel
        w1 = h*240//320  # change the height to fit the render image
        x1 = (w-w1)//2  # midpoint of width without resizing
        frame = frame[:, x1:x1+w1]  # crop into the center
        frame = cv2.resize(frame, (240, 320))  # resize according to the screen keeping the aspect ratio 
        frame = cv2.flip(frame,1)  # Rotate horizontally 180 °
        frame = cv2.rotate(frame, cv2.ROTATE_90_COUNTERCLOCKWISE)
        '''Display real-time video stream'''
        cv2.imshow('winname',frame)  # Display image img on winname window
        key = cv2.waitKey(1)  # Refresh the image every 1ms, and the delay cannot be 0, otherwise the read result will be a static frame
        if key & 0xFF == ord('a'):  # Press the A key to enter the save image operation below
            cv2.imwrite(str(index) + ".png", frame)
            print("save" + str(index) + ".png successfuly!")
            print("-------------------------")
            index += 1
            # lz = cv2.VideoWriter('/root/video/output.mp4',fourcc,3,(240,320))  # Store video recordings
            # lz.write(frame)  # Storage frame
            # cv2.imshow('cvNamedWindow',frame)  # Display video stream
        '''Press the B key to exit the program'''
        if key & 0xFF == ord('b'):
            break

cap.release()  # Release the camera
cv2.destroyAllWindows()  # Close all