Color image enhancement in HSI color space without gamut problem

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 from HIS color space to RGB color space usually generates the gamut problem after processing intensity and saturation in the HSI color space. In this paper, we clear the relationship between the gamut of RGB color space and that of HSI color space completely. According to the result, we can check whether the processing result is located inside or outside of RGB gamut in the HSI color space easily. If the processing result is judged outside of RGB gamut, we apply to the effective way of hue preserving correction algorithm which is proposed in this paper. Experimental results demonstrate that the proposed algorithm can correct the color distortion caused by the enhancement without reducing the visual effect and it is especially useful for images with rich colors and local high component values.