Python OpenCV从二进制图像中检测白色对象并裁剪它

现在我的OpenCV Python代码可以找到这份白皮书.第一步,我创建了一个用于查找此白皮书的掩码：

正如你们所看到的,小的白噪声和小块已被删除.然后问题变成了如何从这个二进制图像中裁剪这个白皮书对象来制作一个新的子集二进制图像？

我目前的代码是：

import cv2
import numpy as np

QR = cv2.imread('IMG_0352.TIF',0) 
mask = np.zeros(QR.shape,np.uint8) 

contours,hierarchy = cv2.findContours(QR,cv2.RETR_LIST,cv2.CHAIN_APPROX_SIMPLE)

for cnt in contours:
    if cv2.contourArea(cnt)>1000000:
        cv2.drawContours(mask,[cnt],255,-1)

寻找cnt var,有四个元素,但它们对我来说是无稽之谈.
我使用代码来装箱：

x,y,w,h = cv2.boundingRect(cnt)
cv2.rectangle(img,(x,y),(x+w,y+h),(0,0),2)

盒子信息似乎不正确.

谢谢你的任何建议.

跟进：
我已经弄清楚了这个问题,这很容易.代码附后：

import cv2
import numpy as np


QR_orig = cv2.imread('CamR_IMG_0352.TIF',0)
QR = cv2.imread('IMG_0352.TIF',0) # read the QR code binary image as grayscale image to make sure only one layer
mask = np.zeros(QR.shape,np.uint8) # mask image the final image without small pieces

# using findContours func to find the none-zero pieces
contours,cv2.CHAIN_APPROX_SIMPLE)

# draw the white paper and eliminate the small pieces (less than 1000000 px). This px count is the same as the QR code dectection
for cnt in contours:
    if cv2.contourArea(cnt)>1000000:
        cv2.drawContours(mask,-1) # the [] around cnt and 3rd argument 0 mean only the particular contour is drawn

        # Build a ROI to crop the QR
        x,h = cv2.boundingRect(cnt)
        roi=mask[y:y+h,x:x+w]
        # crop the original QR based on the ROI
        QR_crop = QR_orig[y:y+h,x:x+w]
        # use cropped mask image (roi) to get rid of all small pieces
        QR_final = QR_crop * (roi/255)

cv2.imwrite('QR_final.TIF',QR_final)