How to align face images c++ opencv

Question

I am developing a C++ application for face authentication. First, I have to detect the face and pre-process the image.

1. For face detection I have used the HaarC

Answer 1

I have implemented it here using OpenCV & DLib: https://github.com/ManuBN786/Face-Alignment-using-Dlib-OpenCV

Any tilted faces can be aligned using my code.