Opencv_contrib: GMSMatcher Crashes in debug Mode (vector subscript out of range)

[0x23]

Description:
In '_modules/xfeatures2d/src/gms.cpp_' method GMSMatcher::run crashes in Line 373 in debug mode:

373: if (mCellPairs[mvMatchPairs[i].first] == mvMatchPairs[i].second)
374:                mvbInlierMask[i] = true;

This is because array mCellPairs is indexed with mvMatchPairs[i].first which sometimes has value -1. The Value -1 is written to mCellPairs in method assignMatchPairs line 170:

int lgidx = mvMatchPairs[i].first = getGridIndexLeft(lp, gridType);

were getGridIndexLeft() returns -1 if the feature point coordinates are close to the border. See Line 222:

222:    if (x >= mGridSizeLeft.width || y >= mGridSizeLeft.height)
223:        return -1;

Suggested Fix:

Add additional check for mvMatchPairs[i].first in Line 373:

373: if (mvMatchPairs[i].first>=0 && mCellPairs[mvMatchPairs[i].first] == mvMatchPairs[i].second)
374:                mvbInlierMask[i] = true;

[catree]

Can you add some reproducible code and data (e.g. two images saved in a lossless format as png)?

Also, you may want to report the bug in the upstream repository.

[0x23]

I dont have a stand alone exampe for bug reproduction at hand but I think this one can be checked by looking at the code only. I tried to explain the problem above

[alalek]

If this line is under test coverage, they you can try to create Pull Request with patch. CI run automatic tests on it.

[catree]

This has been fixed in the upstream repository, see this comment.

The code in the upstream repository: https://github.com/JiawangBian/GMS-Feature-Matcher/blob/d7e63bb3b1530a6cb183444a5eb27fb0894d0748/include/gms_matcher.h#L411

---

@0x23

Can you open a pull request with the according change?