gcc linking error: undefined reference to symbol '_ZN2cv5flann12SearchParamsC1Eifb',

Question

I am using OpenCv along with Eclipse to implement matching with homography. I am getting the following error while building it:

/usr/bin/ld: ./src/flann.o: undefined reference to symbol '_ZN2cv5flann12SearchParamsC1Eifb'

An image of compilation error.

Here's my code:

#include <stdio.h>
#include <iostream>
#include "opencv2/core/core.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/calib3d/calib3d.hpp"
#include "opencv2/nonfree/nonfree.hpp"

using namespace cv;

void readme();

/** @function main */
int main()
{


  Mat img_object = imread( "/home/gaps/Desktop/DSC00268.JPG");
  Mat img_scene = imread( "/home/gaps/Desktop/chart_1-2_1816185b.jpg" );

  if( !img_object.data || !img_scene.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_object, keypoints_scene;

  detector.detect( img_object, keypoints_object );
  detector.detect( img_scene, keypoints_scene );

  //-- Step 2: Calculate descriptors (feature vectors)
  SurfDescriptorExtractor extractor;

  Mat descriptors_object, descriptors_scene;

  extractor.compute( img_object, keypoints_object, descriptors_object );
  extractor.compute( img_scene, keypoints_scene, descriptors_scene );

  //-- Step 3: Matching descriptor vectors using FLANN matcher
  FlannBasedMatcher matcher;
  std::vector< DMatch > matches;
  matcher.match( descriptors_object, descriptors_scene, matches );

  double max_dist = 0; double min_dist = 100;

  //-- Quick calculation of max and min distances between keypoints
  for( int i = 0; i < descriptors_object.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 3*min_dist )
  std::vector< DMatch > good_matches;

  for( int i = 0; i < descriptors_object.rows; i++ )
  { if( matches[i].distance < 3*min_dist )
     { good_matches.push_back( matches[i]); }
  }

  Mat img_matches;
  drawMatches( img_object, keypoints_object, img_scene, keypoints_scene,
               good_matches, img_matches, Scalar::all(-1), Scalar::all(-1),
               vector<char>(), DrawMatchesFlags::NOT_DRAW_SINGLE_POINTS );

  //-- Localize the object
  std::vector<Point2f> obj;
  std::vector<Point2f> scene;

  for( int i = 0; i < good_matches.size(); i++ )
  {
    //-- Get the keypoints from the good matches
    obj.push_back( keypoints_object[ good_matches[i].queryIdx ].pt );
    scene.push_back( keypoints_scene[ good_matches[i].trainIdx ].pt );
  }

  Mat H = findHomography( obj, scene, CV_RANSAC );

  //-- Get the corners from the image_1 ( the object to be "detected" )
  std::vector<Point2f> obj_corners(4);
  obj_corners[0] = cvPoint(0,0); obj_corners[1] = cvPoint( img_object.cols, 0 );
  obj_corners[2] = cvPoint( img_object.cols, img_object.rows ); obj_corners[3] = cvPoint( 0, img_object.rows );
  std::vector<Point2f> scene_corners(4);

  perspectiveTransform( obj_corners, scene_corners, H);

  //-- Draw lines between the corners (the mapped object in the scene - image_2 )
  line( img_matches, scene_corners[0] + Point2f( img_object.cols, 0), scene_corners[1] + Point2f( img_object.cols, 0), Scalar(0, 255, 0), 4 );
  line( img_matches, scene_corners[1] + Point2f( img_object.cols, 0), scene_corners[2] + Point2f( img_object.cols, 0), Scalar( 0, 255, 0), 4 );
  line( img_matches, scene_corners[2] + Point2f( img_object.cols, 0), scene_corners[3] + Point2f( img_object.cols, 0), Scalar( 0, 255, 0), 4 );
  line( img_matches, scene_corners[3] + Point2f( img_object.cols, 0), scene_corners[0] + Point2f( img_object.cols, 0), Scalar( 0, 255, 0), 4 );

  //-- Show detected matches
  imshow( "Good Matches & Object detection", img_matches );

  waitKey(0);
  return 0;
  }

  /** @function readme */
  void readme()
  { 
std::cout << " Usage: ./SURF_descriptor <img1> <img2>" << std::endl; 
}

but i am not able to find the solution, all the answers to the above mentioned question specify the problem, but any particular solution to it @ AndyG — Gur Amrit Pal Singh, Jan 04 '16 at 15:10
OpenCV could be not installed correctly, or it's not referenced correctly in your path (the compiler cannot find appropriate files). Try to make a much simpler program to recreate the problem first, and then focus on solving those linker errors. — AndyG, Jan 04 '16 at 15:16
all other programs and projects are running fine, except for this one — Gur Amrit Pal Singh, Jan 04 '16 at 15:22
Maybe your make file is wrong? Try to perform a complete clean (removing all intermediate files) and rebuild. — AndyG, Jan 04 '16 at 15:25
Since you have a linkage error, we're in the dark until you post the g++ commandline that performs the failing linkage. Add this information to the question. — Mike Kinghan, Jan 04 '16 at 19:42

score 3 · Accepted Answer · answered Jan 05 '16 at 14:06

3

You are not linking libopencv_flann, in which the undefined symbol is defined. Add -lopencv_flann to your linker options.

answered Jan 05 '16 at 14:06

Mike Kinghan

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gcc linking error: undefined reference to symbol '_ZN2cv5flann12SearchParamsC1Eifb',

1 Answers1