title: Linker issue in opencv
body: <p>I am using OpenCV 2.4.6 in Visual Studio 2012 and I have testing one of the sample programs , name matcher_simple.cpp -- which matches two sample images , image1 and image2.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include "opencv2/core/core.hpp"
  #include "opencv2/features2d/features2d.hpp"
  #include "opencv2/highgui/highgui.hpp"
  #include "opencv2/nonfree/nonfree.hpp"
  #include "opencv2/opencv.hpp"
  
  using namespace cv;
  
  static void help()
  {
      printf("\nThis program demonstrates using features2d detector, descriptor extractor and simple matcher\n"
              "Using the SURF desriptor:\n"
              "\n"
              "Usage:\n matcher_simple &lt;image1&gt; &lt;image2&gt;\n");
  }
  
  int main(int argc, char** argv)
  {
      if(argc != 3)
      {
          help();
          return -1;
      }
  
      //cv::initModule_nonfree();
      Mat img1 = imread(argv[1], CV_LOAD_IMAGE_GRAYSCALE);
      Mat img2 = imread(argv[2], CV_LOAD_IMAGE_GRAYSCALE);
      if(img1.empty() || img2.empty())
      {
          printf("Can't read one of the images\n");
          return -1;
      }
  
  
      // detecting keypoints
      SurfFeatureDetector detector(400);
      vector&lt;KeyPoint&gt; keypoints1, keypoints2;
      detector.detect(img1, keypoints1);
      detector.detect(img2, keypoints2);
  
      // computing descriptors
      SurfDescriptorExtractor extractor;
      Mat descriptors1, descriptors2;
      extractor.compute(img1, keypoints1, descriptors1);
      extractor.compute(img2, keypoints2, descriptors2);
  
      // matching descriptors
      BFMatcher matcher(NORM_L2);
      vector&lt;DMatch&gt; matches;
      matcher.match(descriptors1, descriptors2, matches);
  
      // drawing the results
      namedWindow("matches", 1);
      Mat img_matches;
      drawMatches(img1, keypoints1, img2, keypoints2, matches, img_matches);
      imshow("matches", img_matches);
      waitKey(0);
  
      return 0;
  }
  </code></pre>
  
  <p>On compiling I get this error : </p>
  
  <pre><code>1&gt;------ Build started: Project: opencvreinstated, Configuration: Release x64 ------
  1&gt;matcher_simple.obj : error LNK2001: unresolved external symbol "public: __cdecl cv::SURF::SURF(void)" (??0SURF@cv@@QEAA@XZ)
  1&gt;matcher_simple.obj : error LNK2001: unresolved external symbol "public: __cdecl cv::SURF::SURF(double,int,int,bool,bool)" (??0SURF@cv@@QEAA@NHH_N0@Z)
  1&gt;C:\Users\motiur\documents\visual studio 2012\Projects\opencvreinstated\x64\Release\opencvreinstated.exe : fatal error LNK1120: 2 unresolved externals
  ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
  </code></pre>
  
  <p>I have testing this in release mode 64 bit , I also have successfully ran simple other opencv samples , for example streaming live video . I did not have these sort of issues there . Help is appreciated . Thanks.</p>