Spatio-chromatic model for colour image processing

Traditional colour image enhancement techniques, have ignored the design of the human visual system and have treated colour images as three independent grayscale images. Contrary to this the authors first discuss an opponent colour model of the early visual system and demonstrate it's use in spatial enhancement of both image brightness and chroma. 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 results in an achromatic and two opponent chromatic channels. Laplacian based edge enhancement is then performed independently on each channel. The spatial enhancement of chroma highlights small colour detail and enhances colour 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.