Detecting salient cues through illumination-invariant color ratios

This work presents a novel technique for embedding color constancy into a saliency-based system for detecting potential landmarks in outdoor environments. Sincemultiscale color opponencies are among the ingredients determining saliency, the ideais to make such opponencies directly invariant to illumination variations, rather thanenforcing the invariance of colors themselves. The new technique is compared againstthe alternative approach of preprocessing the images with a color constancy procedurebefore entering the saliency system. The first procedure used in the experimentalcomparison is the well-known image conversion to chromaticity space, and the secondone is based on successive lighting intensity and illuminant color normalizations. Theproposed technique offers significant advantages over the preceding two ones since, ata lower computational cost, it exhibits higher stability in front of illumination variationsand even of slight viewpoint changes, resulting in a better correspondence of visualsaliency to potential landmark elements.