Second Order Stationarity and Spatiochromatic Properties of Natural Images

In this contribution we show that two basic assumptions on the covariance matrices of color images are enough to explain the appearance of spatiochromatic features given by Fourier descriptors in the luminance plus color opponent channels. The first of these assumptions is second order stationarity while the second one is commutativity between color correlation matrices. The validity of these assumptions are experimentally studied on two large image databases. As a lateral result of this study, we also provide novel data to support an exponential decay law of the spatiochromatic covariance between pairs of pixels as a function of their spatial distance instead of the commonly assumed power-law behavior.