title: OpenCV 2.1: where is ostream operator<< for cv::Mat?
body: <p>Following <a href="https://stackoverflow.com/questions/7970988/print-out-the-values-of-a-mat-matrix-in-opencv-c">this question</a>, I am attempting to print out the contents of a <code>cv::Mat</code> to standard output:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;opencv/cv.h&gt;
  #include &lt;opencv/cv.hpp&gt;
  #include &lt;opencv/cxcore.h&gt;
  #include &lt;opencv/cxcore.hpp&gt;
  
  int main() {
  
    cv::Mat m = cv::Mat::ones(10, 10, CV_32S);
    std::cout &lt;&lt; m &lt;&lt; "\n";
  
  }
  </code></pre>
  
  <p>This results in the error</p>
  
  <pre><code>error: no match for ‘operator&lt;&lt;’ in ‘std::cout &lt;&lt; m’
  </code></pre>
  
  <p>I am using gcc 4.6.1 on Ubuntu 11.10, and installed opencv, excluding the examples, following <a href="https://help.ubuntu.com/community/OpenCV" rel="nofollow noreferrer">these instructions</a>. My question is, is the operator available in 2.1 and if so, how do I get it?</p>