cv::flann::index::knnsearch values of indices and dists

opencv3
c++

asked 2016-02-02 14:47:41 -0600

phirestalker
21 ●1 ●4

updated 2016-02-02 21:22:08 -0600

ok given the following code

    index.knnSearch(mat,indices,dists,3);

when using binary descriptors how do I make dists results into a useful ratio or percentage match?

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"a useful ratio or percentage match" -- describing what ?

the smaller the distance, the closer your mat is to the retrieved items

berak ( 2016-02-02 23:56:52 -0600 )edit

Thanks I did some reading and I think I've got a formula

phirestalker ( 2016-02-03 00:13:01 -0600 )edit

oh, please tell us ?

berak ( 2016-02-03 00:22:48 -0600 )edit

it returns the amount of differing bits between the 2 matches. so for 500 descriptors at 32 BYTES each so 256 bits, 256 X 500 descriptors 128,000 bits per set of descriptors so a 90% match would mean a value of 12,800 so anything lower than that is a good match

phirestalker ( 2016-02-03 00:29:10 -0600 )edit

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bool goodMatch(int distance, float percent, int descriptornum) { int descriptorbits = 256 * descriptornum; int result = descriptorbits - (descriptorbits * percent); return (distance <= result); }

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Just some style: "return (distance <= result);"

FooBar ( 2016-02-05 13:54:09 -0600 )edit

thanks, edited

phirestalker ( 2016-02-05 13:57:01 -0600 )edit

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cv::flann::index::knnsearch values of indices and dists

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cv::flann::index::knnsearch values of indices and dists