Adaptive low bit rate facial feature enhanced residual image coding method using SPIHT for compressing personal ID images

Personal identification (ID) image of a person is the main source of authentication in security systems. To retrieve an ID image quickly from the server, a very small sized image file is required. This is achieved by lossy compression of the image. In this paper we propose a method for compressing an ID image below 1 KB that gives good visual quality of the facial features. Discrete Wavelet Transform (DWT) based on CDF 9/7 wavelet filter is used to transform the image. The image is encoded with SPIHT coding at a given rate of bpp. Maxshift method is applied to the residual matrix for the facial features and encoded with SPIHT at another rate of bpp. Both the encoded bit streams are sent to the client. At the client side both the bit streams are decoded and applied with inverse wavelet transformation separately. The images are added to get the reconstructed image. Experimental results show that this method gives better visual quality of the face than that of SPIHT at bpp < 0.1.