Abstract
This paper proposes a method for contrast improvement to generate an output image with a balance of higher contrast and visual naturalness. In the proposed method, not only a distribution of all gray-levels in an input image but also a distribution of quadratic differential values at all pixels are used for generating Look-Up-Table. Both a histogram to represent a distribution of gray-levels and a histogram to represent a distribution of quadratic differential values are generated. The frequency of a gray-level is divided by the frequency of the corresponding quadratic differential values to avoid from the increase of noises and from the too strong contrast enhancement with the saturation of brightness. The output images by the proposed method had good balance of higher contrast and visual naturalness without many noises and brightness saturation.
