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Minimal area rectangle for multiple contours

asked 2018-03-02 04:12:25 -0500

updated 2018-03-05 09:36:15 -0500

I have a case with several contours

std::vector<std::vector<cv::Point>> contours;

I want to get the smallest area rectangle RotatedRect containing all these contours. I have tried minAreaRect() but it returns an exception (probably because I pass it more than one contour).

What would be the best way of getting the minimal area rectangle when you're dealing with more than one contour?

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You want a rotated rectangle containing all the contours in the vector, our just a bounding box enclosing all the contours?

Pedro Batista gravatar imagePedro Batista ( 2018-03-02 05:02:02 -0500 )edit

A rotated rectangle, but bonus points if the answer includes bounding box as well! :-)

Björn Larsson gravatar imageBjörn Larsson ( 2018-03-02 05:06:41 -0500 )edit

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answered 2018-03-02 05:28:11 -0500

berak gravatar image

both minAreaRect() and boundingRect() expect a single contour, not a std::vector<std::vector<cv::Point>>

you'll have to build a single vector<Point> , and then apply your favourite function:

vector<Point> joined;
for (size_t i=0; i<contours.size(); i++) {
      joined.insert(joined.end(), contours[i].begin(), contours[i].end());
}

boundingRect(joined);
minAreaRect(joined);
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Thanks, that solved my problem! :-)

Björn Larsson gravatar imageBjörn Larsson ( 2018-03-02 09:55:48 -0500 )edit

@berak, a little explanation for the code and how it solves the problem, please..

questerer gravatar imagequesterer ( 2018-03-19 00:54:23 -0500 )edit
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Asked: 2018-03-02 04:12:25 -0500

Seen: 357 times

Last updated: Mar 02