Normalized Log Twicing Function for DC Coefficients Scaling in LAB Color Space

Abstract

The brightness of hand held captured images using cameras or camcorders usually differ in the color of the actual scene. These images suffer from the poor contrast values and are having non uniform illumination. There is always a scope to improve the contrast and illustration outward show of the true color metaphors. This piece mainly focuses on the contrast enhancement methods using DC coefficient scaling in the DCT domain. The performance of the conventional DC coefficient scaling is compared in different color spaces as YCbCR and LAB. Based on comparison, it is proposed to scale the DC coefficient in the CIE-Lab color space. Our prime contribution is to propose a novel mapping function by merging the log transformation and the standard Twicing function. The mapped function is then normalized using optimum constants to achieve better visual appearance. The contrast of only L components of LAB space is enhanced, but chrominance information terms are kept preserved. This provides the improved entropy of the enhanced images. The performance is compared using statistical parameters as SNR, entropy and standard deviation difference. The method are trialling on true color image of different environments.