According to module principle of the visual information processing

a novel color constancy color image enhancement algorithm under variable illumination in two steps is presented. After estimating the color offset of original image using the pixels near edges

it can correct the color offset with white balance.Then based on the correlation characteristic of three components in RGB color space

the RGB three components of color image are enhanced at the same proportion by brightness gain curved surface which ensures the hue is constant and undistorted.The algorithm overcomes the ill-posed problems of traditional color constancy algorithm. Experimental results indicated the proposed algorithm can better maintain the color constancy with the images under variable illumination which was color offset or lower illuminance

and simultaneously it can effectively lift the brightness information.