A perceptually tuned embedded zerotree image coder
Embedded zerotree wavelet coding (EZW), introduced by Shapiro (1993) and improved by Said and Pearlman (1996) using an algorithm based on set partitioning in hierarchical trees (SPIHT), is a computationally inexpensive image coding technique and has proven to be very effective at minimizing the mean-square error (MSE) distortion measure. However, minimizing MSE does not guarantee preservation of good perceptual qualities in the decoded image, especially at low bit rates. In this paper we propose a perceptually-tuned embedded zerotree image codec (PEZ) that introduces a perceptual weighting to the wavelet transform coefficients prior to EZW encoding. In this coder the EZW minimizes a perceptually based distortion measure instead of MSE. The perceptual weights for all subbands are computed based on the just noticeable distortion (JND) thresholds for uniform noise. The new perceptually tuned codec has the same complexity as the original EZW/SPIHT techniques and results in a comparable or superior coding performance. Coding results are presented to illustrate the performance of the new coder.