title: openCV SURF error
body: <p><strong>i'm using opencv 2.44 , viusal studio c++ 2010</strong>
  when i compliel i get this error </p>
  
  <blockquote>
    <p>Error 1   error LNK2019: unresolved external symbol "public: __thiscall cv::SURF::SURF(void)" (??0SURF@cv@@QAE@XZ) referenced in function _main   C:\Users\user\Desktop\proiect\prj\prj\sh1.obj   prj</p>
  </blockquote>
  
  <pre><code>#include &lt;opencv2\imgproc\imgproc_c.h&gt;
  #include &lt;stdio.h&gt;
  #include &lt;math.h&gt;
  #include &lt;opencv\highgui.h&gt;
  #include &lt;opencv\cv.h&gt;
  #include &lt;opencv2/features2d/features2d.hpp&gt;
  #include &lt;opencv2/calib3d/calib3d.hpp&gt;
  #include &lt;opencv2/core/core.hpp&gt;
  #include &lt;opencv2/nonfree/features2d.hpp&gt;
  using namespace cv;
  void main(){
  char i; 
  Mat image,img,ref;
  ref=imread("hh.jpg");
  // create window to show image 
  namedWindow("window", CV_WINDOW_AUTOSIZE);
  namedWindow("costel", CV_WINDOW_AUTOSIZE);
  namedWindow("fanel", CV_WINDOW_AUTOSIZE);
  Mat ig,ib,ibb;
  Mat bkg;
  Mat prev;
  Mat stor;
  cvtColor(ref, ref, CV_BGR2GRAY);
  FastFeatureDetector detector(15);
  vector&lt;KeyPoint&gt; keypoints1;
  detector.detect(ref, keypoints1);
  SurfDescriptorExtractor extractor;
  Mat descriptors1;
  extractor.compute(ref, keypoints1, descriptors1);
  
  ....
  </code></pre>