title: Returning Mat object from native code to java in OpenCV
body: <p>I have an OpenCV Android app. Most of its code is in Java but I have
  one function that is in C.
  The function gets a Mat object and returns a new one.</p>
  
  <p>My question is how do I return a Mat from the native code to Java?
  Couldn't find any example of that.</p>
  
  <p>Thanks. </p>