在 python 中使用 cv2.findContours() 时，我的 python 代码出现了 ValueError。 -> 没有足够的值来解包（预期 3，得到 2）答案

【问题标题】：My python code had a ValueError while using cv2.findContours() in python. -> not enough values to unpack (expected 3, got 2)在 python 中使用 cv2.findContours() 时，我的 python 代码出现了 ValueError。 -> 没有足够的值来解包（预期 3，得到 2）
【发布时间】：2020-07-30 16:04:17
【问题描述】：

当我试图运行它时，shell 抛出了一个错误：第 48 行，在 nada,contours,nada = cv2.findContours(frame5.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE) ValueError：没有足够的值来解包（预期 3，得到 2）

请帮我解决它。提前致谢。

# master frame
master = None

while 1:

    # grab a frame
    (grabbed,frame0) = camera.read()

    # end of feed
    if not grabbed:
        break

    # gray frame
    frame1 = cv2.cvtColor(frame0,cv2.COLOR_BGR2GRAY)

    # blur frame
    frame2 = cv2.GaussianBlur(frame1,(15,15),0)

    # initialize master
    if master is None:
        master = frame2
        continue

    # delta frame
    frame3 = cv2.absdiff(master,frame2)

    # threshold frame
    frame4 = cv2.threshold(frame3,15,255,cv2.THRESH_BINARY)[1]

    # dilate the thresholded image to fill in holes
    kernel = np.ones((2,2),np.uint8)
    frame5 = cv2.erode(frame4,kernel,iterations=4)
    frame5 = cv2.dilate(frame5,kernel,iterations=8)

    # find contours on thresholded image
    nada,contours,nada = cv2.findContours(frame5.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)

    # make coutour frame
    frame6 = frame0.copy()

    # target contours
    targets = []

    # loop over the contours
    for c in contours:

        # if the contour is too small, ignore it
        if cv2.contourArea(c) < 500:
                continue

        # contour data
        M = cv2.moments(c)#;print( M )
        cx = int(M['m10']/M['m00'])
        cy = int(M['m01']/M['m00'])
        x,y,w,h = cv2.boundingRect(c)
        rx = x+int(w/2)
        ry = y+int(h/2)
        ca = cv2.contourArea(c)

        # plot contours
        cv2.drawContours(frame6,[c],0,(0,0,255),2)
        cv2.rectangle(frame6,(x,y),(x+w,y+h),(0,255,0),2)
        cv2.circle(frame6,(cx,cy),2,(0,0,255),2)
        cv2.circle(frame6,(rx,ry),2,(0,255,0),2)

        # save target contours
        targets.append((cx,cy,ca))

    # make target
    mx = 0
    my = 0
    if targets:

        # average centroid adjusted for contour size
        #area = 0
        #for x,y,a in targets:
        #    mx += x*a
        #    my += y*a
        #    area += a
        #mx = int(round(mx/area,0))
        #my = int(round(my/area,0))

        # centroid of largest contour
        area = 0
        for x,y,a in targets:
            if a > area:
                mx = x
                my = y
                area = a


    # plot target
    tr = 50
    frame7 = frame0.copy()
    if targets:
        cv2.circle(frame7,(mx,my),tr,(0,0,255,0),2)
        cv2.line(frame7,(mx-tr,my),(mx+tr,my),(0,0,255,0),2)
        cv2.line(frame7,(mx,my-tr),(mx,my+tr),(0,0,255,0),2)

    # update master
    master = frame2

    # display
    cv2.imshow("Frame0: Raw",frame0)
    cv2.imshow("Frame1: Gray",frame1)
    cv2.imshow("Frame2: Blur",frame2)
    cv2.imshow("Frame3: Delta",frame3)
    cv2.imshow("Frame4: Threshold",frame4)
    cv2.imshow("Frame5: Dialated",frame5)
    cv2.imshow("Frame6: Contours",frame6)
    cv2.imshow("Frame7: Target",frame7)

    # key delay and action
    key = cv2.waitKey(1) & 0xFF
    if key == ord('q'):
        break
    elif key != 255:
        print('key:',[chr(key)])

# release camera
camera.release()

# close all windows
cv2.destroyAllWindows()

【问题讨论】：

标签： python opencv typeerror nonetype

【解决方案1】：

这个问题是基于你的一个非常简单的要求。

nada,contours,nada = cv2.findContours(frame5.copy(),cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)

你期望这个函数有 3 个变量，但它只返回两个。你可以阅读库规范，看看你做错了什么。

【讨论】：