无法正确获取轮廓

我正在玩opencv并做下面的简单任务。

1)读取图像

2)阈值

3)寻找轮廓。

4)在空白图像中绘制所有轮廓。

5)绘制单个轮廓。

在虚拟图像上绘制所有等高线看起来不错,而绘制单个等高线会生成分散的等高线,如下图所示。

原件:

所有轮廓:

单轮廓:

请在下面找到代码。

import  cv2
import numpy as np

#Reading Image.
srcImg = cv2.imread("./bottle.jpeg")

#Color Conversion.

grayedImg = cv2.cvtColor(srcImg,cv2.COLOR_RGB2GRAY)
__, thresholdedImg = cv2.threshold(grayedImg, 240, 255, cv2.THRESH_BINARY)

#Noice Removal
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (3,3))
erodeImage = cv2.erode(thresholdedImg,kernel, iterations=1)
dilatedImg = cv2.dilate(erodeImage,kernel, iterations=1)
_, contours, _ = cv2.findContours(dilatedImg,cv2.RETR_TREE,cv2.CHAIN_APPROX_SIMPLE)

#draw All Contours.

dummyImg = np.zeros(grayedImg.shape, dtype=grayedImg.dtype)
cv2.drawContours(dummyImg, contours, -1, 255, 1)
cv2.imshow("All Contours", dummyImg)
cv2.imwrite("allContours.jpeg",dummyImg)

#draw Individual Contours.

mask =  np.zeros(dummyImg.shape[:2], dtype= dummyImg.dtype)
isolatedImg = cv2.drawContours(mask, contours[9], -1, 255, 1)

cv2.imshow("Indivial Contours.", isolatedImg)
cv2.imwrite("single.jpeg",isolatedImg)

cv2.waitKey(0)