Hue-preserving local contrast enhancement and illumination compensation for outdoor color images
Marco Tektonidis, David Monnin, Frank M. Christnacher · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2015
Real-time applications in the field of security and defense use dynamic color camera systems to gain a better understanding of outdoor scenes. To enhance details and improve the visibility in images it is required to per- form local image processing, and to reduce lightness and color inconsistencies between images acquired under different illumination conditions it is required to compensate illumination effects. We introduce an automatic hue-preserving local contrast enhancement and illumination compensation approach for outdoor color images. Our approach is based on a shadow-weighted intensity-based Retinex model which enhances details and compensates the illumination effect on the lightness of an image. The Retinex model exploits information from a shadow detection approach to reduce lightness halo artifacts on shadow boundaries. We employ a hue-preserving color transformation to obtain a color image based on the original color information. To reduce color inconsistencies between images acquired under different illumination conditions we process the saturation using a scaling function. The approach has been successfully applied to static and dynamic color image sequences of outdoor scenes and an experimental comparison with previous Retinex-based approaches has been carried out.