title: how to use "shape_predictor_68_face_landmarks.dat" in landmark extraction in opencv C++ using Dlib
body: <p>I'm trying to run the following code and detect the facial landmarks of the frames which are taken from webcam.</p>
  
  <pre><code>#include &lt;dlib/opencv.h&gt;
  #include &lt;opencv2/highgui/highgui.hpp&gt;
  #include &lt;dlib/image_processing/frontal_face_detector.h&gt;
  #include &lt;dlib/image_processing/render_face_detections.h&gt;
  #include &lt;dlib/image_processing.h&gt;
  #include &lt;dlib/gui_widgets.h&gt;
  
  using namespace dlib;
  using namespace std;
  
  int main()
  {
      try
      {
          cv::VideoCapture cap(0);
          if (!cap.isOpened())
          {
              cerr &lt;&lt; "Unable to connect to camera" &lt;&lt; endl;
              return 1;
          }
  
          image_window win;
  
          // Load face detection and pose estimation models.
          frontal_face_detector detector = get_frontal_face_detector();
          shape_predictor pose_model;
          deserialize("shape_predictor_68_face_landmarks.dat") &gt;&gt; pose_model;
  
          // Grab and process frames until the main window is closed by the user.
          while(!win.is_closed())
          {
              // Grab a frame
              cv::Mat temp;
              cap &gt;&gt; temp;
              // Turn OpenCV's Mat into something dlib can deal with.  Note that this just
              // wraps the Mat object, it doesn't copy anything.  So cimg is only valid as
              // long as temp is valid.  Also don't do anything to temp that would cause it
              // to reallocate the memory which stores the image as that will make cimg
              // contain dangling pointers.  This basically means you shouldn't modify temp
              // while using cimg.
              cv_image&lt;bgr_pixel&gt; cimg(temp);
  
              // Detect faces 
              std::vector&lt;rectangle&gt; faces = detector(cimg);
              // Find the pose of each face.
              std::vector&lt;full_object_detection&gt; shapes;
              for (unsigned long i = 0; i &lt; faces.size(); ++i)
                  shapes.push_back(pose_model(cimg, faces[i]));
  
              // Display it all on the screen
              win.clear_overlay();
              win.set_image(cimg);
              win.add_overlay(render_face_detections(shapes));
          }
      }
      catch(serialization_error&amp; e)
      {
          cout &lt;&lt; "You need dlib's default face landmarking model file to run this example." &lt;&lt; endl;
          cout &lt;&lt; "You can get it from the following URL: " &lt;&lt; endl;
          cout &lt;&lt; "   http://dlib.net/files/shape_predictor_68_face_landmarks.dat.bz2" &lt;&lt; endl;
          cout &lt;&lt; endl &lt;&lt; e.what() &lt;&lt; endl;
      }
      catch(exception&amp; e)
      {
          cout &lt;&lt; e.what() &lt;&lt; endl;
      }
  }
  </code></pre>
  
  <p>But when executing this .cpp file it gives the console output like this.</p>
  
  <p><a href="https://i.stack.imgur.com/BCwQz.png" rel="nofollow noreferrer">enter image description here</a></p>
  
  <p>As in this I have download shape_predictor_68_face_landmarks.dat. But I don't know where to add this .dat and whish directory to include. Could anyone tell me how to use this shape_predictor_68_face_landmarks.dat.</p>