opencv - orb descriptor computation on provided keypoints -

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i using opencv 2.4.8. declaring orb such:

int patchsize = 31; orb orb(1000,1.0f,1,patchsize,0,2,orb::harris_score,patchsize);

doesn't patch size mean there should (patchsize-1)/2 space around keypoint?

i providing keypoints @ coordinates 15 pixels margins vertically , horizontally, such positions fail produce descriptors.

for example, image 240x320 point (15,15) fails described, though there enough pixels ( 0,1,....14 -> 15 pixels).

opencv uses keypointsfilter::runbyimageborder selected edgethreshold (which patchsize) eliminate keypoints close image border orb computation (the file modules/features2d/src/orb.cpp, if want have look; line 669 in computekeypoints).

so margin 31, , not 15.

hope helps!


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