title: With OpenCV, try to extract a region of a picture described by ArrayOfArrays
body: <p>I am developing some image processing tools in iOS. Currently, I have a contour of features computed, which is of type InputArrayOfArrays.</p>
  
  <p>Declared as:</p>
  
  <pre><code>std::vector&lt;std::vector&lt;cv::Point&gt; &gt; contours_final( temp_contours.size() );
  </code></pre>
  
  <p>Now, I would like to extract areas of the original RGB picture circled by contours and may further store sub-image as cv::Mat format. How can I do that?</p>
  
  <p>Thanks in advance!</p>