为什么我会在 OpenCV 中收到这个 SimpleBlobDetector 错误？

如何解决为什么我会在 OpenCV 中收到这个 SimpleBlobDetector 错误？

我正在运行从 https://learnopencv.com/blob-detection-using-opencv-python-c/ 复制的以下代码并得到如下所示的错误。错误消息没有帮助。代码在 OpenCV4.2 中进行了测试。只是想知道新版本是否有一些语法变化。

# Standard imports
import cv2
import numpy as np;

# Read image
im = cv2.imread("blob.jpg")

# Setup SimpleBlobDetector parameters.
params = cv2.SimpleBlobDetector_Params()

# Change thresholds
params.minThreshold = 10
params.maxThreshold = 200


# Filter by Area.
params.filterByArea = True
params.minArea = 1500

# Filter by Circularity
params.filterByCircularity = True
params.minCircularity = 0.1

# Filter by Convexity
params.filterByConvexity = True
params.minConvexity = 0.87

# Filter by Inertia
params.filterByInertia = True
params.minInertiaratio = 0.01

# Create a detector with the parameters
# OLD: detector = cv2.SimpleBlobDetector(params)
detector = cv2.SimpleBlobDetector_create(params)


# Detect blobs.
keypoints = detector.detect(im)

# Draw detected blobs as red circles.
# cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS ensures
# the size of the circle corresponds to the size of blob

im_with_keypoints = cv2.drawKeypoints(im,keypoints,np.array([]),(0,255),cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS)

# Show blobs
cv2.imshow("Keypoints",im_with_keypoints)
cv2.waitKey(0)

以下是错误信息。 回溯（最近一次调用）：

文件“”，第 44 行，在 im_with_keypoints = cv2.drawKeypoints(im,cv2.DRAW_MATCHES_FLAGS_DRAW_RICH_KEYPOINTS)

错误：OpenCV(4.5.2) C:\Users\runneradmin\AppData\Local\Temp\pip-req-build-vi271kac\opencv\modules\imgproc\src\color.cpp:182: 错误：(- 215：断言失败) !_src.empty() 在函数 'cv::cvtColor'