Abstract: According to the detail preserving and color constancy problems in the low illumination image enhancement processing,this paper proposed a novel Retinex enhancement algorithm based on Lab color space and color mapping image contrast.Firstly,the input image of Lab color space with a low contrast is decomposed into luminance and chrominance components,and adaptive bilateral filtering is used for estimation of illumination intensity,so that appropriate adjacent pixels can be considered according to the brightness and color values.Then the tone mapping function based on the parabola is used to improve the contrast of the estimation of illumination image.Finally,the enhanced brightness and the original chroma are combined together to produce an enhanced color output image.Experimental results show that the proposed algorithm can enhance the image details and edge structure by reducing the image artifacts, and can preserve the image’s nature by avoiding the color shift.

Key words: Low illumination,Color image enhancement,Lab color space,Tone mapping,Retinex,Color shift