Retinex Image Processing: Improving the Visual Realism of Color Images

Sensations of color show a strong correlation with reflectance, even though the amount of visible light reaching the eye depends on the product of reflectance and illumination. The visual system must achieve this remarkable result by a scheme that does not measure flux. Such a scheme is described as the basis of Retinex theory. This paper deals with image enhancement techniques basically Retinex and its constituents, namely Small Scale Retinex (SSR), Multi Scale Retinex (MSR) and Multi Scale Retinex with Color Restoration (MSRCR). The techniques enable color rendition and dynamic range compression in case of ‘dark’ or ‘low lit’ images. The Multi Scale Retinex (MSR) is a generalization of the SSR, which, in turn, is based upon the last version of Land’s center/surround retinex. The current version, the multi scale Retinex with color restoration (MSRCR), combines the dynamic range compression and color constancy of the MSR with a color ‘restoration’ filter that provides excellent color rendition. The MSRCR has been tested on a very large suite of images. We provide a general overview of the types of operations that can be performed on the image in order to enhance its quality.