A Space-Variant Luminance Map based Color Image Enhancement

Improvement of image quality has been highly demanding for users in digital imaging systems. A variety of image enhancement algorithms has been developed to control image enhancement factors. This paper presents a color image enhancement method that makes use of a space-variant luminance map (SVLM) for the local brightness characterization. Two-dimensional gamma correction combined with the SVLM is developed to increase the intensity at the dark region and vice versa at the bright region in the luminance domain. The enhanced luminance information is applied to the adaptive contrast enhancing process and the linear color restoration. The proposed algorithm reveals details of the input image as well as minimizes loss of the edge sharpness in the non-uniform and low illumination conditions. The developed enhancement process resulted in the lowest absolute mean brightness error (AMBE) in a low-complexity fashion. A series of experimental results are discussed in terms of visual quality, the enhancement performance, and the complexity.