title: OpenCV Identifying Lines and Curves
body: <p>I'm just starting to learn OpenCV programming. May I just ask about how can I identify lines and curves in OpenCV? My problem is that I have to identify if the image contains a convex or concave (horizontal or vertical curve) curve, a vertical, diagonal or a horizontal line.</p>
  
  <p>In my code, I used <code>CvSetImageROI</code> to take a particular part of an image, and then I'm trying to identify each according to the said lines/curves.</p>
  
  <p>Are there functions in OpenCV that are available? Thank you very much for the help. By the way, i'm using Linux and C++.</p>