OpenCV Python调整大小图像

我正在尝试将轮廓尺寸调整为28x28像素，并将其通过我的模型以检测数字并显示它。但是，我对function有问题cv2.resize()。这是我的代码：

ret, frame = cap.read()

if ret == False:
    continue
gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
blurred = cv2.GaussianBlur(gray, (5, 5), 0)
edged = cv2.Canny(blurred, 50, 200, 255)

# Threshold the image
threshold = cv2.adaptiveThreshold(edged, 255, cv2.ADAPTIVE_THRESH_GAUSSIAN_C, cv2.THRESH_BINARY_INV, 11, 4)

# Find contours in the image
_, contours, _= cv2.findContours(threshold, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)


# ******************************************************************* #
# Get rectangles contains each contour
rects = [cv2.boundingRect(ctr) for ctr in contours]

for rect in rects:
    # Draw the rectangles
    cv2.rectangle(frame, (rect[0], rect[1]), (rect[0] + rect[2], rect[1] + rect[3]), (0, 255, 0), 3) 

    # Make the rectangular region around the digit
    leng = int(rect[3] * 1.6)
    pt1 = int(rect[1] + rect[3] // 2 - leng // 2)
    pt2 = int(rect[0] + rect[2] // 2 - leng // 2)

    height, width = frame.shape[:2]

    if pt1+leng > width or pt2+leng > height:
        continue;

    roi = frame[pt1:pt1+leng, pt2:pt2+leng]

    # Resize the image
    roi = cv2.resize(roi, (28, 28), cv2.INTER_AREA)
    roi = cv2.dilate(roi, (3, 3))

    #nbr = clf.predict(np.array([roi_hog_fd], 'float64'))
    #cv2.putText(frame, str(int(nbr)), (rect[0], rect[1]),cv2.FONT_HERSHEY_DUPLEX, 1, (0, 0, 255), 3)
    cv2.putText(frame, "2", (rect[0], rect[1]),cv2.FONT_HERSHEY_DUPLEX, 1, (0, 0, 255), 3)

我得到的错误是：

错误：C：\ projects \ opencv-python \ opencv \ modules \ imgproc \ src \ resize.cpp：4044：错误：（-215）函数cv :: resize中的ssize.width> 0 && ssize.height> 0

调整视频原始帧的大小（之前未应用任何其他cv2功能）效果很好。

有什么建议么？