识别图像中的圆并在圆周边中获得4个像素（点）

Question

我需要用圆圈处理图像以识别圆圈。 然后从内部圆到圆的外围需要4个像素点。

到目前为止，我已经在this blog的帮助下对此代码进行了编程：

import numpy as np
import cv2
import argparse

def imageProcessing():
    ap=argparse.ArgumentParser()
    ap.add_argument("-i","--image",required=True,help="path to image")
    args=vars(ap.parse_args())

    # load the image, clone it for output, and then convert it to grayscale
    image = cv2.imread(args["image"])
    output = image.copy()
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)

    # detect circles in the image
    circles = cv2.HoughCircles(gray,cv2.HOUGH_GRADIENT, 1.2, 100)

    # ensure at least some circles were found
    if circles is not None:
        # convert the (x, y) coordinates and radius of the circles to integers
        circles = np.round(circles[0, :]).astype("int")

        # loop over the (x, y) coordinates and radius of the circles
        for (x, y, r) in circles:
            # draw the circle in the output image, then draw a rectangle
            # corresponding to the center of the circle
            cv2.circle(output, (x, y), r, (0, 255, 0), 4)
            cv2.rectangle(output, (x - 5, y - 5), (x + 5, y + 5), (0, 128, 255), -1)

        # show the output image
        cv2.imshow("output", np.hstack([image, output]))
        cv2.waitKey(0)

if __name__=="__main__":
    imageProcessing()

它可以在简单的图像中识别圆，如下所示：

但是无法识别下图中我需要处理的圆圈：

您能指出我犯的错误吗？为什么程序无法识别圆？

也指导我如何在内圈上获得4分。