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AlgorithmInfo does not name a type

I am now trying to use the surf module provided in /opencv2/nonfree. There is an error here: /usr/include/opencv2/nonfree/features2d.hpp:132:5: error: ‘AlgorithmInfo’ does not name a type AlgorithmInfo* info() const; Any solution for it ?The following is my original code copied from the website of OpenCV tutorial: `/** * @file SURF_FlannMatcher * @brief SURF detector + descriptor + FLANN Matcher * @author A. Huaman */

include <stdio.h>

include <iostream>

include "opencv2/core/core.hpp"

using namespace std; //order for include and using namespace is crucial using namespace cv;

include "opencv2/features2d/features2d.hpp"

include "opencv2/highgui/highgui.hpp"

include "opencv2/nonfree/features2d.hpp"

include "opencv2/nonfree/nonfree.hpp"

void readme();

/* * @function main * @brief Main function */ int main( int argc, char* argv ) { cv::initModule_nonfree(); 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, //-- or a small arbitary value ( 0.02 ) in the event that min_dist is very //-- small) //-- 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 <= max(2*min_dist, 0.02) ) { 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 < (int)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; }`

AlgorithmInfo does not name a type

I am now trying to use the surf module provided in /opencv2/nonfree. There is an error ~~here:~~ here:

/usr/include/opencv2/nonfree/features2d.hpp:132:5: error: ‘AlgorithmInfo’ does not name a type
     AlgorithmInfo* info() const;

Any solution for it ?The following is my original code copied from the website of OpenCV ~~tutorial:~~ tutorial:

`/**
 * @file SURF_FlannMatcher
 * @brief SURF detector + descriptor + FLANN Matcher
 * @author A. Huaman
 */
 include <stdio.h>
 include <iostream>
 include "opencv2/core/core.hpp"
 */

#include <stdio.h>
#include <iostream>
#include "opencv2/core/core.hpp"
using namespace std;
//order for include and using namespace is crucial
using namespace cv;
 include "opencv2/features2d/features2d.hpp"
 include "opencv2/highgui/highgui.hpp"
 include "opencv2/nonfree/features2d.hpp"
 include "opencv2/nonfree/nonfree.hpp"
 cv;
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/nonfree/features2d.hpp"
#include "opencv2/nonfree/nonfree.hpp"
void readme();
 /*
readme();

/**
 * @function main
 * @brief Main function
 */
int main( int argc, char* char** argv )
{
  cv::initModule_nonfree();
  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;
 400;

  SurfFeatureDetector detector( minHessian );
 std::vector<keypoint> );

  std::vector<KeyPoint> keypoints_1, keypoints_2;
 keypoints_2;

  detector.detect( img_1, keypoints_1 );
  detector.detect( img_2, keypoints_2 );
 );

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

  Mat descriptors_1, descriptors_2;
 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;
 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,
  //-- or a small arbitary value ( 0.02 ) in the event that min_dist is very
  //-- small)
  //-- PS.- radiusMatch can also be used here.
  std::vector< DMatch > good_matches;
 good_matches;

  for( int i = 0; i < descriptors_1.rows; i++ )
  { if( matches[i].distance <= max(2*min_dist, 0.02) )
    { 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 < (int)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);
 }

  waitKey(0);

  return 0;
}
 }

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