title: How are two-element vector represented in a OpenCV Mat in Java?
body: <p>I was looking at <a href="http://docs.opencv.org/java/2.4.2/org/opencv/imgproc/Imgproc.html#HoughLines%28org.opencv.core.Mat,%20org.opencv.core.Mat,%20double,%20double,%20int%29">Opencv Java documentation of Hough Transform</a>.</p>
  
  <p>The return value <code>lines</code> is in a <code>Mat</code> data type described as:</p>
  
  <blockquote>
    <p>Output vector of lines. Each line is represented by a two-element
    vector (rho, theta). rho is the distance from the coordinate origin
    (0,0) (top-left corner of the image). theta is the line rotation angle
    in radians (0 ~ vertical line, pi/2 ~ horizontal line).</p>
  </blockquote>
  
  <p>Curiously, this description matches <a href="http://docs.opencv.org/modules/imgproc/doc/feature_detection.html?highlight=houghlines#houghlines">the C++ interface's description</a>, <strong>but</strong> the data type not: in C++ you can use a <code>std::vector&lt;cv::Vec2f&gt; lines</code> as described in <a href="http://docs.opencv.org/doc/tutorials/imgproc/imgtrans/hough_lines/hough_lines.html#standard-and-probabilistic-hough-line-transform">this tutorial</a>. In C++ the returned data representation, given the description, is straightforward, but in Java not.</p>
  
  <p>So, in Java, how are the two-element vector represented/stored in the returned Mat?</p>