Why is a contour from cv2.findContours() in a shape like [N,1,2]?

asked 2020-09-28 00:13:53 -0600

Eric Song
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updated 2020-09-28 01:02:41 -0600

berak
32993 ●7 ●81 ●312

Hi, guys,
I am a learner of OpenCV, and I found the returned contours from cv2.findContours() are in a a shape like [N,1,2]?
And I want to know why not using the shape as [N,2]?
What is the reason for the middle dimension?

Any idea or answer will be appreciated!

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answered 2020-09-28 03:09:56 -0600

berak
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opencv is a c++ library, the automatically generated python wrappers have some oddities...

since a std::vector<Point> has to be the equivalent of a cv::Mat(N,1,CV_32SC2) (a 2d matrix !) in c++, you'll get it translated like this into python