Fuzzy Spatial Ranks for Object Recognition Across Illumination Changes

In this paper, we propose an original scheme to retrieve among all the target images of a database, those which contain the same object as that represented by the query image, these images being acquired under different illumination conditions. Rather than considering the color vectors of the pixels to characterize the images, we propose to introduce and exploit the concept of spatial ranks of CCD sensor responses. Indeed, these values are preserved in case of illumination changes and they take into account both the colors of the pixels and the spatial interactions between them in the image. Since we can not determine these ranks from a color image, we propose to estimate their probabilities of occurrences thanks to fuzzy functions. These probabilities are used by our object recognition scheme whose effectiveness is assessed with a public database that contains images of objects acquired under different illuminations