Hi Raghuveer,
You can easily retrieve the relative positions of the key points of the face. Then you can apply some technique to get your "emotion". The easiest on is to define a few archetypes (let say the tradition Ekmann 6 emotions) in term of those key point
position, then you do nearest neighbhoor. Not the most robust but easy to implement...
For more you can use machine learning to get the mapping from key points to emotions.
