Model-based face image coding using spherical harmonics

A model-based image coding technique combines image processing, computer vision and computer graphics techniques to achieve higher coding efficiency. Traditional model-based image coding techniques encode the motion in an image sequence as changes of model parameters, thus very low bit rates can be achieved for video coding. We present a novel method to improve coding efficiency of face images. The key idea is to use a spherical harmonic representation of illumination and a generic face geometric model to encode the variation of appearance produced by diffuse reflection. We show that this method improves coding efficiency. This method is complementary to other model-based image coding techniques.