Color image enhancement in improved HSI color space

While enhancing the intensity or saturation component for high-quality color enhancement, keeping the hue component unchanged is important; thus, perceptual color models such as HSI and HSV were used. Hue-Saturation-Intensity (HSI) is a public color model, and many color applications are commonly based on this model. However, the transformation form HSI model to RGB model usually generates the gamut problem after processing intensity and saturation in the HSI model. Moreover, the saturation component is always increased or decreased following the change of intensity component no matter what the attainable saturation range is. In this paper, we propose accurate formulas for the color transformation between RGB and the proposed HSI color model which is named the improved HSI (I-HSI) color model. Furthermore, we show a simple enhancement method of color images based on the gamma transformation. In experiments, we show the validity of the I-HSI color model under the comparison with the conventional HSI color model.