opencv python中的限制扫描区域

如何解决opencv python中的限制扫描区域

我有一个二维码扫描仪的代码。如何限制这样的扫描区域？
https://www.checkfront.com/wp-content/uploads/2017/08/Android-Mobile-QR-Scanner.png
在照片中，您可以找到扫描区域。我试图在网上搜索我的问题。但不幸的是，我没有找到有用的东西。希望你能帮助我。谢谢

代码：

import cv2
import numpy as np
import sys
import time
import pyzbar.pyzbar as pyzbar

cap = cv2.VideoCapture(0)
hasFrame,frame = cap.read()
vid_writer = cv2.VideoWriter('output.avi',cv2.VideoWriter_fourcc('M','J','P','G'),10,(frame.shape[1],frame.shape[0]))

# display barcode and QR code location
def display(im,decodedobjects):

  # Loop over all decoded objects
  for decodedobject in decodedobjects:
    points = decodedobject.polygon

    # If the points do not form a quad,find convex hull
    if len(points) > 4 :
      hull = cv2.convexHull(np.array([point for point in points],dtype=np.float32))
      hull = list(map(tuple,np.squeeze(hull)))
    else :
      hull = points;

    # Number of points in the convex hull
    n = len(hull)

    # Draw the convext hull
    for j in range(0,n):
      cv2.line(im,hull[j],hull[ (j+1) % n],(255,0),3)

  # display results
  # cv2.imshow("Results",im);

# Create a qrCodeDetector Object
qrDecoder = cv2.QRCodeDetector()

# Detect and decode the qrcode
t = time.time()
while(1):
    hasFrame,inputimage = cap.read()
    if not hasFrame:
        break
    decodedobjects = pyzbar.decode(inputimage)
    if len(decodedobjects):
        zbarData = decodedobjects[0].data
    else:
        zbarData=''
    opencvData,bBox,rectifiedImage = qrDecoder.detectAndDecode(inputimage)
    if zbarData:
        cv2.putText(inputimage,"ZBAR : {}".format(zbarData),(10,50),cv2.FONT_HERShey_SIMPLEX,1,(0,255,2,cv2.LINE_AA)
    else:
        cv2.putText(inputimage,"ZBAR : QR Code NOT Detected",255),cv2.LINE_AA)
    if opencvData:
        cv2.putText(inputimage,"OpenCV:{}".format(opencvData),150),"OpenCV:QR Code NOT Detected",cv2.LINE_AA)

    display(inputimage,decodedobjects)
    cv2.imshow("Result",inputimage)
    vid_writer.write(inputimage)
    k = cv2.waitKey(20)
    if k == 27:
        break
cv2.destroyAllWindows()
vid_writer.release()