SimpleBlobDetector opencv python error but missing output

Question

I am trying to work with the opencv SimpleBlobDetector. My current program is a simple test program like this:

import cv2
import numpy as np;

im = cv2.imread("blobs.jpg", cv2.IMREAD_GRAYSCALE)

params = cv2.SimpleBlobDetector_Params()

params.filterByArea = True;
params.minArea = 1;
params.maxArea = 1000;

detector = cv2.SimpleBlobDetector(params)

keypoints = detector.detect(im)

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

cv2.imshow("Keypoints", im_with_keypoints)
cv2.waitKey(0)

code runs until the keypoints line where it should actually detect the blobs. it doesnt show any error message but just restarts the kernel. i used a very easy picture so blobs should be detected.

used image

Paddy Harrison · Accepted Answer · 2020-05-04 11:17:59Z

1

Seems to work for me. If you are using Python 3 you want to use detector = cv2.SimpleBlobDetector_create(params) rather than what you had before. I increased the max area to 10000 pixels and I've included a screenshot of the output too:

import cv2
import numpy as np;

im = cv2.imread("blobs.jpg", cv2.IMREAD_GRAYSCALE)

params = cv2.SimpleBlobDetector_Params()

params.filterByArea = True;
params.minArea = 1;
params.maxArea = 10000;

detector = cv2.SimpleBlobDetector_create(params)

keypoints = detector.detect(im)

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

cv2.imshow("Keypoints", im_with_keypoints)
cv2.waitKey(0)

answered May 4, 2020 at 11:17

Paddy Harrison

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1 Comment

o.st. Over a year ago

If you are using Python 3 you want to use detector = cv2.SimpleBlobDetector_create(params). That one did the job. thanks a lot.

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