Blue sky color is an important memory color for outdoor photography. Reproducing it pleasingly is essential for preferred color reproduction of photographic images. A simple approach for enhancing blue sky color is to detect blue sky colors and then enhance all sky blue pixels regardless of their object types. However, this method has a negative effect for modifying blue colors of non-sky objects. In this paper, we present an improved method for detecting the sky region of images captured with digital cameras, followed with a method to enhance blue sky colors for visually pleasing results. Treatment of white sky colors (overexposed sky colors and white clouds) and sunset and sunrise warm sky colors are presented as well.
Huanzhao Zeng, "Sky Color Enhancement of Photographic Images" in Proc. IS&T Int’l. Symp. on Electronic Imaging: Color Imaging XXII: Displaying, Processing, Hardcopy, and Applications, 2017, pp 168 - 170, https://doi.org/10.2352/ISSN.2470-1173.2017.18.COLOR-055