使用FLANN进行特征点匹配

「爱情、让人受尽委屈。」 2022-08-19 08:37 265阅读 0赞

# 使用FLANN进行特征点匹配 #

## 目标 ##

在本教程中我们将涉及以下内容:

*  使用 [FlannBasedMatcher][] 接口以及函数 [FLANN][] 实现快速高效匹配( *快速最近邻逼近搜索函数库(Fast Approximate Nearest Neighbor Search Library)* )

## 理论 ##

## 代码 ##

这个教程的源代码如下所示。你还可以从 [以下链接下载得到源代码][Link 1]

#include <stdio.h>
    #include <iostream>
    #include "opencv2/core/core.hpp"
    #include "opencv2/features2d/features2d.hpp"
    #include "opencv2/highgui/highgui.hpp"
    
    using namespace cv;
    
    void readme();
    
    /** @function main */
    int main( int argc, char** argv )
    {
          
      if( argc != 3 )
      {
           readme(); return -1; }
    
      Mat img_1 = imread( argv[1], CV_LOAD_IMAGE_GRAYSCALE );
      Mat img_2 = imread( argv[2], CV_LOAD_IMAGE_GRAYSCALE );
    
      if( !img_1.data || !img_2.data )
      {
           std::cout<< " --(!) Error reading images " << std::endl; return -1; }
    
      //-- Step 1: Detect the keypoints using SURF Detector
      int minHessian = 400;
    
      SurfFeatureDetector detector( minHessian );
    
      std::vector<KeyPoint> keypoints_1, keypoints_2;
    
      detector.detect( img_1, keypoints_1 );
      detector.detect( img_2, keypoints_2 );
    
      //-- Step 2: Calculate descriptors (feature vectors)
      SurfDescriptorExtractor extractor;
    
      Mat descriptors_1, descriptors_2;
    
      extractor.compute( img_1, keypoints_1, descriptors_1 );
      extractor.compute( img_2, keypoints_2, descriptors_2 );
    
      //-- Step 3: Matching descriptor vectors using FLANN matcher
      FlannBasedMatcher matcher;
      std::vector< DMatch > matches;
      matcher.match( descriptors_1, descriptors_2, matches );
    
      double max_dist = 0; double min_dist = 100;
    
      //-- Quick calculation of max and min distances between keypoints
      for( int i = 0; i < descriptors_1.rows; i++ )
      {
           double dist = matches[i].distance;
        if( dist < min_dist ) min_dist = dist;
        if( dist > max_dist ) max_dist = dist;
      }
    
      printf("-- Max dist : %f \n", max_dist );
      printf("-- Min dist : %f \n", min_dist );
    
      //-- Draw only "good" matches (i.e. whose distance is less than 2*min_dist )
      //-- PS.- radiusMatch can also be used here.
      std::vector< DMatch > good_matches;
    
      for( int i = 0; i < descriptors_1.rows; i++ )
      {
           if( matches[i].distance < 2*min_dist )
        {
           good_matches.push_back( matches[i]); }
      }
    
      //-- Draw only "good" matches
      Mat img_matches;
      drawMatches( img_1, keypoints_1, img_2, keypoints_2,
                   good_matches, img_matches, Scalar::all(-1), Scalar::all(-1),
                   vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );
    
      //-- Show detected matches
      imshow( "Good Matches", img_matches );
    
      for( int i = 0; i < good_matches.size(); i++ )
      {
           printf( "-- Good Match [%d] Keypoint 1: %d  -- Keypoint 2: %d  \n", i, good_matches[i].queryIdx, good_matches[i].trainIdx ); }
    
      waitKey(0);
    
      return 0;
     }
    
     /** @function readme */
     void readme()
     {
           std::cout << " Usage: ./SURF_FlannMatcher <img1> <img2>" << std::endl; }

## 解释 ##

## 结果 ##

1.  这里是第一张图特征点检测结果:
    
    ![../../../../\_images/Featur\_FlannMatcher\_Result.jpg][.._.._.._.._images_Featur_FlannMatcher_Result.jpg]
2.  此外我们通过控制台输出FLANN匹配关键点结果:
    
    ![../../../../\_images/Feature\_FlannMatcher\_Keypoints\_Result.jpg][.._.._.._.._images_Feature_FlannMatcher_Keypoints_Result.jpg]原文：[http://www.opencv.org.cn/opencvdoc/2.3.2/html/doc/tutorials/features2d/feature\_flann\_matcher/feature\_flann\_matcher.html][http_www.opencv.org.cn_opencvdoc_2.3.2_html_doc_tutorials_features2d_feature_flann_matcher_feature_flann_matcher.html]

[FlannBasedMatcher]: http://opencv.willowgarage.com/documentation/cpp/features2d_common_interfaces_of_descriptor_matchers.html?#FlannBasedMatcher
[FLANN]: http://opencv.willowgarage.com/documentation/cpp/flann_fast_approximate_nearest_neighbor_search.html#
[Link 1]: https://code.ros.org/svn/opencv/trunk/opencv/samples/cpp/tutorial_code/features2D/SURF_FlannMatcher.cpp
[.._.._.._.._images_Featur_FlannMatcher_Result.jpg]: /images/20220731/47b8ae91e1884c4d80e53cc412e1527d.png
[.._.._.._.._images_Feature_FlannMatcher_Keypoints_Result.jpg]: http://www.opencv.org.cn/opencvdoc/2.3.2/html/_images/Feature_FlannMatcher_Keypoints_Result.jpg
[http_www.opencv.org.cn_opencvdoc_2.3.2_html_doc_tutorials_features2d_feature_flann_matcher_feature_flann_matcher.html]: /images/20220731/652e6af6a1f443bfa278c75d16c217b9.png