Local correlations, information redundancy, and the sufficient pixel depth in natural images.
by Yury Petrov and Li Zhaoping,
Published in Journal of Optical Society of America, A. Vol. 20. No. 1, p56-66, 2003
Abstract: A mathematical framework which enables the factorization of a joint probability distribution into its localized components for a two-dimensional array of pixels is presented. The factorization was used to estimate the contribution to mutual information due to two-(I2 ) and three-pixel (I3) luminance correlations for a large ensemble of natural images analysed at various spatial scales and pixel depths b. It is shown that both I2 and I3 saturate around b ~ 6 bits/pixel. Three-pixel correlations are shown to produce only a marginal increase of information redundancy (4%) over two-pixel correlation (50%). Implications for neural representation in visual cortex are discussed.