VARIABLE BLOCK SIZE CODING OF IMAGES WITH HYBRID QUANTIZATION

This paper describes a progressive image transmission (PIT) scheme usi ng a variable block size coding technique in conjunction with a variet y of quantization schemes in the transform domain, The proposed scheme uses a region growing technique to partition the images so that regio ns of different sizes can be addressed using a small amount of side in formation. This segmentation divides the image into five different reg ions that vary in size based on the details within the image. High-det ail blocks are classified into four different categories based on the energy distribution followed by vector quantization (VQ), and low-deta il blocks are encoded with scalar quantization (SQ). Progressive refin ement is achieved by proper masking of the information in the transfor m domain. Simulation results show that the reconstructed images preser ve fine and pleasant qualities based on both subjective and mean squar e error criteria. Also, the receiver reconstructs more details in each stage so that the observer can recognize the image quickly.