title: fatal error: opencv2/contrib/contrib.hpp' file not found (open cv already built)
body: <p>I have downloaded and built open cv according to these <a href="http://docs.opencv.org/3.0-last-rst/doc/tutorials/introduction/linux_install/linux_install.html" rel="nofollow noreferrer">open cv docs</a>.</p>
  
  <p>I am trying to compile this <a href="http://docs.opencv.org/modules/contrib/doc/facerec/facerec_tutorial.html" rel="nofollow noreferrer">Eigenfaces demo</a>, and I am getting the following error.</p>
  
  <pre><code>fatal error: 'opencv2/contrib/contrib.hpp' file not found
  </code></pre>
  
  <p>The line of concern is</p>
  
  <pre><code>#include "opencv2/contrib/contrib.hpp"
  </code></pre>
  
  <p>The contrib directory is not in my <code>usr/local/include/opencv/</code> directory. I have referenced the following <a href="https://stackoverflow.com/questions/28222067/mac-osx-build-opencv-contrib-fatal-error-file-not-found-opencv2-core-hpp">SO Question</a>, but it seems to only handle the case of building from scratch.</p>
  
  <p>Also, the repository that it references <a href="https://github.com/Itseez/opencv_contrib" rel="nofollow noreferrer">opencv_contrib</a> does not even contain the file <code>contrib.hpp</code></p>
  
  <p>How can I simply add the necessary source files to my current build without having to completely rebuild everything?</p>