title: How can I install opencv2 with brew under OSX
body: <p>Recently, I installed opencv with the following command:</p>
  
  <pre><code>brew install opencv
  </code></pre>
  
  <p>I found opencv3 was installed in dir <code>/usr/include</code> and <code>/usr/lib</code>. But what I want is opencv2. How can install opencv2 with the <code>brew</code> command?</p>