Spatio-chromatic ICA of a Mosaiced Color Image

We analyze whether Independant Component Analysis (ICA) is an appropriate tool for estimating spatial information in spatiochromatic mosaiced color images. In previous studies, ICA analysis of natural color scenes (Hoyer et al. 2000; Tailor et al., 2000; Wachtler et al., 2001; Lee et al. 2002) have shown the emergence of achromatic patterns that can be used for luminance estimation. However, these analysis are based on fully defined spatio-chromatic images, i.e. three or more chromatic values per pixel. In case of a reduced spatio-chromatic set with a single chromatic measure per pixel, such as present in the retina or in CFA images, we found that ICA is not an appropriate tool for estimating spatial information. By extension, we discuss that the relationship between natural image statistics and the visual system does not remain valid if we take into account the spatio-chromatic sampling by cone photoreceptors.