Color image enhancement method with adjustable emphasis degree

This paper presents a new color image enhancement method. In color image processing, hue preserving is required. The proposed method is performed into the ideal HSI color space whose gamut is same as the RGB color space. The differential gray-level histogram equalization (DHE) is effective for the enhancement of gray scale images. The proposed method is an extension version of the DHE for color images, and furthermore, the enhancement degree is variable by introducing two parameters. Since our enhancement method is applied to not only intensity but also saturation, both the contrast and the colorfulness of the output image can be varied. We clear that the contrast and the colorfulness are controlled by the intensity enhancement method and the saturation enhancement method, respectively. The two enhancement methods are almost independent. Therefore, the intensity enhancement and the saturation enhancement are performed simultaneously, and can be changed the degree of emphasis by using two parameters.