title: How to align face images c++ opencv
body: <p>I am developing a C++ application for face authentication. First, I have to detect the face and pre-process the image.</p>
  
  <ol>
  <li>For face detection I have used the HaarCascadeClassifier. The problem is that the this tool or this algorithm gives me a facial region detected by a little bit large rectangle that englobes hair and some of the background. Is there a solution to change the dimension of this rectangle? I used "frontalfacecascaadclassifier.xml".</li>
  <li>For face pre-processing i want to do face alignment exactly like <a href="http://www.bytefish.de/blog/aligning_face_images">this technique</a>. How would I go about accomplishing this?</li>
  </ol>