title: How to convert a java collection of images to CvArr
body: <p>I want to use OpenCV's <code>FaceRecognition</code> in java through <em>javacv</em> wrapper library.
  I don't know how to pass images and labels to <code>com.googlecode.javacv.cpp.opencv_contrib.FaceRecognizer.train(CvArr, CvArr)</code></p>
  
  <p>I can use <code>cvLoadImage(String)</code> or <code>cvLoadImageM(String)</code> to obtain single images, but how do I make an <code>CvArr</code> of them?</p>