PiQ: Perceptual Image Quantizer for Wavelet Image Coders

摘要

The aim of this work is to explain how to apply perceptual criteria in order to define a perceptual forward and inverse quantizer. We present its application to the Hi-SET coder. Our approach consists in quantizing wavelet transform coefficients using some of the human visual system behavior properties. Taking in to account that noise is fatal to image compression performance, because it can be both annoying for the observer and consumes excessive bandwidth when the imagery is transmitted. Perceptual quantization reduces unperceivable details and thus improve both visual impression and transmission properties. The comparison between JPEG2000 coder and the combination of Hi-SET with the proposed perceptual quantizer (χSET) shows that the latter is not favorable in PSNR than the former, but the recovered image is more compressed (less bit-rate) at the same or even better visual quality measured with well-know image quality metrics, such as MSSIM, UQI or VIF, for instance.