A modified hue and range preserving color assignment function with a component-wise saturation adjustment for color image enhancement

Abstract

This paper presents a new approach to enhancing color images by modifying an affine color assignment function. This function maps colors to pixels of the enhanced gray-scale image in a way that improves the visual quality of the image, particularly in darker regions. The main goal of our method is to finely adjust saturation, correct saturation loss in specific image regions, and preserve the original image’s range and hue. Our proposed method follows a two-step process. First, it enhances the intensity image using a combination of global and local histogram equalization methods. This results in an overall improved appearance by redistributing pixel intensities and enhancing contrast. Then, modified color mapping functions are applied to assign colors to each pixel of the enhanced gray-scale image. The aim is to adjust saturation by amplifying the maximally saturated color image. Additionally, we introduce two new color-weighted maps to evaluate pixel importance from the maximally saturated image. This contributes to saturation control in the final enhanced image. Compared to alternative color mapping algorithms, our model preserves the original color of pixels in challenging areas and fine-tunes saturation based on parameter settings.