<title>Spatiochromatic model for color image enhancement</title>

Abstract

Traditionally the development of color image enhancement techniques has not taken the design of the human visual system into account. Color images have been treated in much the same way as achromatic images and only brightness has been enhanced. In this study we first discuss an opponent color model of the early visual system and then we show the benefit of performing spatial enhancement on both brightness and chroma in the context of the model. The opponent transform is calculated such that cone redundancies are reduced and information compressed, similar to the way it is performed in the visual system. This is done using a multispectral Karhunen-Loeve transform. This results in an achromatic and two opponent chromatic channels, one red-green and the other blue-yellow. Laplacian based edge enhancement is then performed independently on each channel. The spatial enhancement of chroma highlights small color detail and enhances color edges thus increasing image detail in areas where achromatic enhancement has no effect. Due to spatial limitations of the visual system, the best enhanced image is obtained when both achromatic and chromatic edge enhancement are used together.