A Wavelet VQ Image Compression System

Abstract

The discrete wavelet transform (DWT) is a powerful technique for image compression because of its flexibility in representing image and its ability in adapting to the human visual system characteristics. This paper presents a new wavelet compression technique that mainly contains a modified search order coding (SOC) for lowest band and crossband vector quantization (VQ) for higher bands. For each lowest-band coefficient, a searching scheme is employed to find out the matched coefficient, within a tolerable distortion, from the previous coefficients, and then the corresponding search order of the matched coefficient is sent to the decoder. For higher bands, there exists correlation among the coefficients of different resolution levels (or scales). We employ a crossband vector quantization technique with a novel weighted distortion measure to exploit the correlation efficiently. The simulation results indicate that the new wavelet-based technique achieves good picture quality at very low bit rate.