Added code for SURF using FLANN Matcher and drawMatches options

samples/cpp/tutorial_code/features2D/SURF_FlannMatcher.cpp

+/**
+ * @file SURF_FlannMatcher
+ * @brief SURF detector + descriptor + FLANN Matcher
+ * @author A. Huaman
+ */
+
+#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
+ * @brief Main function
+ */
+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_descriptor <img1> <img2>" << std::endl; }