OpenCV错误：试图将图像放置在网络摄像机源上时，在setSize中断言失败（s>=0）

Question

我试图在一个网络摄像头的feed中把一个帽子的图像覆盖在头上，我得到了下面一行的错误-

hat = cv2.resize(imghat, (hatWidth,hatHeight), interpolation = cv2.INTER_AREA)

程序运行，但很快退出并出现上述错误。代码段如下-

# Create the mask for the hat
imghatGray = cv2.cvtColor(imghat, cv2.COLOR_BGR2GRAY)
#cv2.imwrite("imghatGray.png", imghatGray)

ret, orig_mask = cv2.threshold(imghatGray, 0, 255, cv2.THRESH_BINARY)
#cv2.imwrite("orig_mask.png", orig_mask)

# Create the inverted mask for the hat
orig_mask_inv = cv2.bitwise_not(orig_mask)
#cv2.imwrite("orig_mask_inv.png", orig_mask_inv)

# Convert hat image to BGR
# and save the original image size (used later when re-sizing the image)
imghat = imghat[:,:,0:3]
orighatHeight, orighatWidth = imghat.shape[:2]

video_capture = cv2.VideoCapture(0)

while True:

    ret, frame = video_capture.read()

    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    faces = face_cascade.detectMultiScale(gray, 1.3, 5, flags=cv2.cv.CV_HAAR_SCALE_IMAGE)

    for (x, y, w, h) in faces:
        cv2.rectangle(frame, (x,y), (x+w, y+h), (255,0,0), 2)

        roi_gray = gray[y:y+h, x:x+w]
        roi_color = frame[y:y+h, x:x+w]

        hatWidth = w
        hatHeight = hatWidth * orighatHeight / orighatWidth

        # Center the hat
        x1 = x -15
        x2 = x + hatWidth + 15
        y1 = y - hatHeight
        y2 = y + 15

        # Check for clipping
        if x1 < 0:
            x1 = 0
        if y1 < 0:
            y1 = 0
        if x2 > w:
            x2 = w
        if y2 > h:
            y2 = h

        cv2.rectangle(frame, (x1,y1), (x2, y2), (0,255,0), 2)

        # Re-calculate the width and height of the hat image
        hatWidth = x2 - x1
        hatHeight = y2 - y1

        # Re-size the original image and the masks to the hat sizes
        # calcualted above
        hat = cv2.resize(imghat, (hatWidth,hatHeight), interpolation = cv2.INTER_AREA)
        mask = cv2.resize(orig_mask, (hatWidth,hatHeight), interpolation = cv2.INTER_AREA)
        mask_inv = cv2.resize(orig_mask_inv, (hatWidth,hatHeight), interpolation = cv2.INTER_AREA)

        # take ROI for hat from background equal to size of hat image
        roi = roi_color[y1:y2, x1:x2]

        # roi_bg contains the original image only where the hat is not
        # in the region that is the size of the hat.
        roi_bg = cv2.bitwise_and(roi,roi,mask = mask_inv)

        # roi_fg contains the image of the hat only where the hat is
        roi_fg = cv2.bitwise_and(hat,hat,mask = mask)

        # join the roi_bg and roi_fg
        dst = cv2.add(roi_bg,roi_fg)

        # place the joined image, saved to dst back over the original image
        roi_color[y1:y2, x1:x2] = dst

        break

这是显示的错误消息-

v2.error:/home/vinravun/opencv-2.4.10/modules/core/src/matrix.cpp:116:错误：（-215）s>；=0（函数设置大小）