Abstract
This paper proposes a method for improving saturation in the context of hue-preserving color image enhancement. The proposed method handles colors in an RGB color space, which has the form of a cube, and enhances the contrast of a given image by histogram manipulation, such as histogram equalization and histogram specification, of the intensity image. Then, the color corresponding to a target intensity is determined in a hue-preserving manner, where a gamut problem should be taken into account. We first project any color onto a surface in the RGB color space, which bisects the RGB color cube, to increase the saturation without a gamut problem. Then, we adjust the intensity of the saturation-enhanced color to the target intensity given by the histogram manipulation. The experimental results demonstrate that the proposed method achieves higher saturation than that given by related methods for hue-preserving color image enhancement.
Highlights
Image enhancement is the process of the quality improvement of an image for both human viewers and other automated image processing techniques [1]
When the luminance or intensity is predetermined by an appropriate contrast enhancement technique, which is the case that we discuss in this paper, we can improve the colorfulness by increasing saturation while preserving hue
We evaluated the performance with the color colorfulness index (CCI) defined in (10) in [4] as shown in Figure 17, where the vertical and horizontal axes denote the CCI value and image numbers, respectively
Summary
Image enhancement is the process of the quality improvement of an image for both human viewers and other automated image processing techniques [1]. When the luminance or intensity is predetermined by an appropriate contrast enhancement technique, which is the case that we discuss in this paper, we can improve the colorfulness by increasing saturation while preserving hue. We propose a method for hue-preserving saturation improvement by eliminating the middle part, where Yang and Lee’s method is the same as that of Naik and Murthy, which decreases the saturation.
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