获取openCV错误：在RaspberryPi 3上的python中断言失败（scn == 3 || scn == 4）

Question

我正按照此处显示的步骤尝试制作手势控制灯 https://makezine.com/projects/raspberry-pi-potter-wand/

但是我遇到了一个问题，我不断收到断言

def TrackWand():

    global rval,old_frame,old_gray,p0,mask,color,ig,img,frame
    color = (0,0,255)
    rval, old_frame = cam.read()
    cv2.flip(old_frame,1,old_frame)
    old_gray = cv2.cvtColor(old_frame, cv2.COLOR_BGR2GRAY)
    equalizeHist(old_gray,old_gray)
    old_gray = GaussianBlur(old_gray,(9,9),1.5)
    dilate_kernel = np.ones(dilation_params, np.uint8)
    old_gray = cv2.dilate(old_gray, dilate_kernel, iterations=1)
    # Take first frame and find circles in it
    p0 = cv2.HoughCircles(old_gray,cv2.cv.CV_HOUGH_GRADIENT,3,100,param1=100,param2=30,minRadius=4,maxRadius=15)
    try:
            p0.shape = (p0.shape[1], 1, p0.shape[2])
            p0 = p0[:,:,0:2] 
    except:
            print ("No points found")         
# Create a mask image for drawing purposes
    mask = np.zeros_like(old_frame)

    while True:
            rval, frame = cam.read()
            cv2.flip(frame,1,frame)
            frame_gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        #equalizeHist(frame_gray,frame_gray)
    #frame_gray = GaussianBlur(frame_gray,(9,9),1.5)
    #dilate_kernel = np.ones(dilation_params, np.uint8)
        #frame_gray = cv2.dilate(frame_gray, dilate_kernel, iterations=1)
            try:     
        # calculate optical flow
                    p1, st, err = cv2.calcOpticalFlowPyrLK(old_gray, frame_gray, p0, None, **lk_params)

        # Select good points
                    good_new = p1[st==1]
                    good_old = p0[st==1]

                # draw the tracks
                    for i,(new,old) in enumerate(zip(good_new,good_old)):
                            a,b = new.ravel()
                            c,d = old.ravel()
                    # only try to detect gesture on highly-rated points (below 15)
                            if (i<15):
                                    IsGesture(a,b,c,d,i)
                            dist = math.hypot(a - c, b - d)
                            if (dist<movment_threshold):
                                    cv2.line(mask, (a,b),(c,d),(0,255,0), 2)
                            cv2.circle(frame,(a,b),5,color,-1)
                            cv2.putText(frame, str(i), (a,b), cv2.FONT_HERSHEY_SIMPLEX, 1.0, (0,0,255))
            except IndexError:
                    print ("Index error")  
                    cam.release()
                    cv2.destroyAllWindows()
                    break          
            except:
                    e = sys.exc_info()[0]
                    print ("Error: %s" % (e,)) 
                    cam.release()
                    cv2.destroyAllWindows()
                    break
            img = cv2.add(frame,mask)

            cv2.putText(img, "Press ESC to close.", (5, 25),
                cv2.FONT_HERSHEY_SIMPLEX, 1.0, (255,255,255))
            cv2.imshow("Raspberry Potter", frame)

        # get next frame
            rval, frame = cam.read()

        # Now update the previous frame and previous points
            old_gray = frame_gray.copy()
            p0 = good_new.reshape(-1,1,2)
            key = cv2.waitKey(20)
            if key in [27, ord('Q'), ord('q')]: # exit on ESC
                    break

这是断言错误

  

初始化点跟踪   错误：模块＆＃39; cv2＆＃39;没有属性＆＃39; cv＆＃39;   OpenCV错误：断言失败（scn == 3 || scn == 4）在cvtColor中，文件/home/pi/opencv-3.3.0/modules/imgproc/src/color.cpp，第10638行   Traceback（最近一次调用最后一次）：     文件＆＃34; rpotter2.py＆＃34;，第202行，in       TrackWand（）
    在TrackWand中输入文件＆＃34; rpotter2.py＆＃34;，第131行       old_gray = cv2.cvtColor（old_frame，cv2.COLOR_BGR2GRAY）   cv2.error：/home/pi/opencv-3.3.0/modules/imgproc/src/color.cpp:10638：错误：（-215）scn == 3 || scn == 4 in function cvtColor

我对此非常陌生，所以任何帮助都会非常感激！