Image coding in the context of a psychovisual image representation with vector quantization
The two main functions, decomposition and quantization, of the coding scheme described are entirely based on psychovisual aspects. From psychophysical experiments, the peripheral parts of the human visual system have been modeled by a set of nineteen channels and a nondirectional low residue. To perform this decomposition, filters similar to the cortex filters have been designed and used. The quantizers have been designed for each of the visual subband by evaluating the perception of quantization impairments on natural images. The images have been characterized by the local bandlimited contrast. It has been shown that these images must always be uniformly quantized in order to achieve a just noticeable quantization noise. The performance of the coding scheme based on the results above have been evaluated in terms of the peak signal to noise ratio, entropy and visual quality. The results show that at medium and low signal to noise ratios the visual quality of the reconstructed image remains much better than for "classical" schemes.