OpenCV代码导致似乎是断言错误

Question

我运行了这段代码，但是我不理解错误以及如何解决

cap = cv2.VideoCapture(0)

while(1):
    _,frame = cap.read()
    hsv = cv2.cvtColor(frame,cv2.COLOR_BGR2HSV)
    lower_blue = np.array([110,50,50])
    upper_blue = np.array([130,255,255])

    mask = cv2.inRange(hsv,lower_blue,upper_blue)
    res = cv2.bitwise_and(frame,frame,mask = mask)

    cv2.imshow('frame',frame)
    cv2.imshow('mask',mask)
    cv2.imshow('res',res)
    k = cv2.waitKey(5) & 0xFF
    if k==27:
        break

cv2.destroyAllWindows()

  

OpenCV（3.4.1）C：\ Miniconda3 \ conda-bld \ opencv-suite_1533128839831 \ work \ modules \ imgproc \ src \ color.cpp：11214：错误：（-215）（scn == 3 || scn == 4）&&（深度== 0 ||深度== 5）在函数cv :: cvtColor

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