问'cv::tracking::impl::TrackerKCFImpl::getSubWindow‘函数中的OpenCV(4.5.5)错误：(-215:断言失败) img.channels() == 3

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  File "C:\Users\angjw\Dropbox\NUS\Blink detection\mov files\Leye blink info extractor_v2.py", line 368, in <module>
    ret, bbox = tracker.update(roi)

error: OpenCV(4.5.5) D:\a\opencv-python\opencv-python\opencv_contrib\modules\tracking\src\trackerKCF.cpp:688: error: (-215:Assertion failed) img.channels() == 3 in function 'cv::tracking::impl::TrackerKCFImpl::getSubWindow'

tracker = cv2.TrackerKCF_create()
while True and frameCount <= COUNTlastframe:
    
    # Read a new frame
    ok, frame = video.read()
    if not ok:
        break   
    
    roi = frame[roiCoor1: roiCoor2, roiCoor3: roiCoor4]
    ## Do a drift correction every 600 frames (10s) (was 500; 8.33s)
    if frameCount % 600 == 0 and blinkStarted == False or frameCount == COUNTfirstframe:
        
        xylocalizer = [0,0,0,0]
        roi = frame[roiCoor1: roiCoor2, roiCoor3: roiCoor4]
        rows, cols, _ = roi.shape
        roi = cv2.cvtColor(roi, cv2.COLOR_BGR2GRAY)
        roi = cv2.GaussianBlur(roi, (7, 7), 0)
        
        _, threshold = cv2.threshold(roi, binaryThreshold, 255, cv2.THRESH_BINARY_INV) #min and max colour values for pupil threshold
        contours, _ = cv2.findContours(threshold, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
        contours = sorted(contours, key=lambda x: cv2.contourArea(x), reverse=True)   
            
        for cnt in contours:
            (x, y, w, h) = cv2.boundingRect(cnt)
            
            #cv2.rectangle(roi, (x, y), (x + w, y + h), (255, 0, 0), 2)
            #cv2.line(roi, (x + int(w/2), y), (x + int(w/2), y+h), (255, 0, 0), 2)
            break    
        
        ## Sum up the xy location of eye for the first xysample seconds.
        ## *1.25 arbitrary value to increase ROI box size for greater detection accuracy. 
        xylocalizer[0] = xylocalizer[0] + x    #x (from left)
        xylocalizer[1] = xylocalizer[1] + y    #y (from top)
        xylocalizer[2] = xylocalizer[2] + w*1.25    #box width
        xylocalizer[3] = xylocalizer[3] + h*1.25    #box height        
        
        tracker = cv2.TrackerKCF_create()
        ok = tracker.init(frame, (int(xylocalizer[0]),int(xylocalizer[1]),int(xylocalizer[2]),int(xylocalizer[3]))) 
        ret, bbox = tracker.update(roi)