Image Compression Using Zerotree and Multi-Stage Vector Quantization

Embedded zerotree of wavelet coef ic ient ( E Z W) algori thm has become a n efSective way of compressing images. T h e use of multistage vector quantizer ( M S V Q ) provides successive-approximation coding f o r vectors. A n e w algorithm i s proposed tha t provides good quality of reconstructed images at very low bit rates. T h e algorithm uses successive-approximation quantization of both scalars and vectors o n wavelet coef ic ients of the image. Successive-approximation quantization of scalars and vectors is done using EZW and M S V Q algorithms respectively. EZ W algorithm is applied t o wavelet coef ic ients belonging to coarser level subbands and M S V Q is applied t o vectors of wavelet coeficients belonging t o f iner level subbands. T h e proposed method further uses static HufSman coding t o achieve more compression.