Nonlinear contrast enhancement based on the Retinex approach

In this paper we present a digital image enhancement technique which relies on the application of a nonlinear operator within the Retinex approach. The basic idea of this approach is to separate the illumination and reflectance components of the image, so that, by reducing the contribution of the former it is possible to effectively-control the dynamic range of the latter. However, its behaviour critically depends on the quality of the illumination estimation process, so that either annoying artifacts are generated, or very complex operators have to be used, which may prevent the use of this method in several cost- and time-sensitive applications. Our method is able to provide, thanks to the use of a suitable nonlinear operator, good quality, artifacts-free images at a limited computational complexity.