title: can't understand following c++ code line
body: <p>I'm new with C++, and try to figuring out what this line of code means:</p>
  
  <pre><code>cur_rect = cv::Rect(cur_rect) &amp; cv::Rect(0, 0, mat-&gt;cols, mat-&gt;rows); // here
  if( cv::Rect(cur_rect) == cv::Rect() )  //here
  {
  .......
  }
  </code></pre>