title: Face detection and image preview drawing
body: <p>I'm developing application that uses DirectShow combined with C++.
  Its main goal is to capture users' faces.
  I have reached the phase when I capture a image from my webcam. 
  The problem is I need an intelligent render. In fact, I need that render to be able to detect a face inside a rectangle. 
  I'm wondring if there is a filter that I can use for this purpose, 
  or if I need to create my own custmized filter. 
  If so enlighten my mind.
  It would look like this: <br>
  <img src="https://i.stack.imgur.com/i8o6F.jpg" alt="enter image description here"></p>
  
  <hr>
  
  <p><strong>I need to understand how I can draw a recangle in my render in the first place. Because otherwise, even if I know the algorithm, I will not be able to  apply it. This is my main goal now.</strong>  </p>
  
  <p>I have some idea but I don't know if they are correct. I think I need to grab each frame separately and apply some modification in some pixels, like what's drawn in the live render.</p>