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POOpenCV: Comparing multiple images using ORB
 

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  1. POOpenCV: Comparing multiple images using ORB
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    <p>I am trying to create a C++ program where there are a lot of images in a list compared to one input image. I got the whole thing working and the program is creating <code>DMatch</code> matches. </p> <p>Now I am trying to determine which of the list of images that is compared to the source image is the best match. I first tried to do this with just comparing how many matches there where between the images, but the problem is that when a generated image has a lot of key-points; they also tend to have a lot of matches, at least in my program.</p> <p>So how can I determine which of the array of images is the best match to the source image? I am using this loop to determine the matches but it doesn't really work:</p> <pre><code>vector&lt; vector&lt;DMatch&gt; &gt; filteredMatches; vector&lt;int&gt; goodIds; Ptr&lt;DescriptorMatcher&gt; matcher(new BFMatcher(NORM_HAMMING, false)); printf("bad matches: "); for(size_t i = 0; i &lt; images.size();i++){ vector&lt;DMatch&gt; matches, good_matches; matcher-&gt;clear(); matcher-&gt;match(images[i], tex_des, matches); if(matches.size() &lt; 8){ printf("F%d,", (int)i + 1); continue; } double min_dist = 100; for(size_t j = 0; j &lt; matches.size(); j++ ){ double dist = matches[j].distance; if( dist &lt; min_dist ) min_dist = dist; } if(min_dist &gt; 50.0){ printf("D%d,", (int)i + 1); continue; } double good_dist = min_dist * 3; for(size_t j = 0; j &lt; matches.size(); j++ ){ if(matches[j].distance &lt; good_dist) good_matches.push_back(matches[j]); } size_t size = good_matches.size(); if(size &lt; 8){ printf("M%d,", (int)i + 1); continue; } vector&lt;Point2f&gt; srcPoints(size); vector&lt;Point2f&gt; dstPoints(size); for(size_t j = 0; j &lt; size; j++){ srcPoints[j] = destination[good_matches[j].trainIdx].pt; dstPoints[j] = keyPoints[i][good_matches[j].queryIdx].pt; } vector&lt;unsigned char&gt; inliersMask(srcPoints.size()); Mat H = findHomography(srcPoints, dstPoints, CV_FM_RANSAC, 3.0, inliersMask); vector&lt;DMatch&gt; inliers; for(size_t j = 0; j &lt; inliersMask.size(); j++){ if(inliersMask[j]){ inliers.push_back(good_matches[j]); } } if(inliers.size() &lt; 4){ printf("S%d,", (int)i + 1); continue; } filteredMatches.push_back(inliers); goodIds.push_back((int)i); H.release(); } printf(" good matches: "); int best = -1; int amount = 0; for(size_t i = 0; i &lt; filteredMatches.size(); i++){ int size = (int)filteredMatches.at(i).size(); if(size &lt; 8) continue; printf("%d,", goodIds[i] + 1); if(amount &lt; size){ amount = size; best = i; } } if(best &gt;= 0) printf(" best match on image: %d, keypoints: %d, ", goodIds[best] + 1, amount); </code></pre> <p>If someone can point me to the functions or the logic I must use I would greatly appreciate it!</p>
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      1. POOpenCV: Comparing multiple images using ORB
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    1. COWhat is the problem with saying "The match with the most inliers is my best match."?
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      1. USTobias Hermann
    2. COThat was the first thing I thought of too, but when I tried it I didn't get any accurate results.
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    3. COOK, so the images (even the false ones) are quite similar I guess. How is the accuracy if you take the average distance of all matches or of all inliers? Can you post example pictures where this fails?
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