cv2.matchShapes（）始终返回0.0

Question

我一直在尝试使用cv2.matchshapes（）比较livefeed的轮廓和图像的轮廓。我用的是 image

这是我正在使用的代码（很抱歉格式太草率）：

import numpy as np
import cv2


cap = cv2.VideoCapture(2)
img1 = cv2.imread('prod1_gray.jpg',0)

ret, thresh_img1 = cv2.threshold(img1, 230, 255, cv2.THRESH_BINARY)

kernel = np.ones((3, 3), np.uint8)
thresh_img1 = cv2.dilate(thresh_img1, kernel, iterations=2)
thresh_img1 = cv2.erode(thresh_img1, kernel, iterations=3)

_, contours_img1, hierarchy = cv2.findContours(thresh_img1, 
cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
if contours_img1:
    cntimg = contours_img1[0]



while True:
    _, frame  = cap.read()
    frame = frame[127:470, 80:550]
    frame_gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
    ret, thresh = cv2.threshold(frame_gray, 230, 255, cv2.THRESH_BINARY)

    kernel = np.ones((3, 3), np.uint8)
    thresh = cv2.dilate(thresh, kernel, iterations=2)
    thresh = cv2.erode(thresh, kernel, iterations=3)

    _, contours, hierarchy = cv2.findContours(thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

    if contours:
        cnt = contours[0]
        area = cv2.contourArea(cnt)
        if area > 30:
            cv2.drawContours(frame, contours, -1, (0, 255, 255), 3)

        ret = cv2.matchShapes(cnt[0], cntimg[0], 1, 0.0)
        print(ret)


    cv2.imshow("Original", frame)
    cv2.imshow("thresh",thresh)
    cv2.imshow("gray", frame_gray)
    cv2.imshow("prod1",img1)


    k = cv2.waitKey(30)
    if k == 27:
        cv2.imwrite("pen.jpg", img1)
        print("cntimg, ",cntimg[0])
        print("cnt, ",cnt[0])
        break

cap.release()
cv2.destroyAllWindows()

由于某些原因，cv2.matchShapes（）总是输出0.0，无论相机前面是什么（没有轮廓）还是像pen这样的随机对象。但它应该输出一个数字，因为笔的形状与原始对象不同。在

我做错什么了？在