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POObject Detection with Hamming distance
 

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  1. POObject Detection with Hamming distance
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    <p>I am using FAST and FREAK to get the descriptors of a couple of images and then I apply knnMatch with a <em>BruteForceMatcher matcher</em> and next I am using a loop to separate the good matches:</p> <pre><code> float nndrRatio = 0.7f; std::vector&lt;KeyPoint&gt; keypointsA, keypointsB; Mat descriptorsA, descriptorsB; std::vector&lt; vector&lt; DMatch &gt; &gt; matches; int threshold=9; // detect keypoints: FAST(objectMat,keypointsA,threshold,true); FAST(sceneMat,keypointsB,threshold,true); FREAK extractor; // extract descriptors: extractor.compute( objectMat, keypointsA, descriptorsA ); extractor.compute( sceneMat, keypointsB, descriptorsB ); BruteForceMatcher&lt;Hamming&gt; matcher; // match matcher.knnMatch(descriptorsA, descriptorsB, matches, 2); // good matches search: vector&lt; DMatch &gt; good_matches; for (size_t i = 0; i &lt; matches.size(); ++i) { if (matches[i].size() &lt; 2) continue; const DMatch &amp;m1 = matches[i][0]; const DMatch &amp;m2 = matches[i][1]; if(m1.distance &lt;= nndrRatio * m2.distance) good_matches.push_back(m1); } //If there are at least 7 good matches, then object has been found if ( (good_matches.size() &gt;=7)) { cout &lt;&lt; "OBJECT FOUND!" &lt;&lt; endl; } </code></pre> <p>I think the problem could be the good matches search method, because using it with the FlannBasedMatcher works fine but with the BruteForceMatcher very weirdly. I'm suspecting that I may be doing a nonsense with this method because the Hamming distance uses binary descriptors, but I can't think of a way to adapt it!</p> <p>Any links, snippets, ideas,... please?</p>
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    1. COSo the problem is that the matches given by the BFMatcher are wrong? How do you initialize it? `cv::BFMatcher(cv::NORM_HAMMING)`?
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    2. COI tried with: `cv::BFMatcher matcher(cv::NORM_HAMMING);` but the results are almost the same. I still think that my problem may be in the latest part...
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    3. COI still don't get your problem. Why do you say that the results are bad?
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