Much of the work done in digital image processing has been limited in application to black-and-white images, this being especially true of enhancement and restoration. The extension to color image processing is not trivial; a suitable color space must be selected for a given application, and then a good processing strategy must be devised. In fact, we doubt that any of the available color spaces will meet the needs of all types of image processing. Many color image processing strategies require that only a luminance component be actually processed. In image restoration, for example, good results are achievable by processing only the Y component of the popular NTSC transformation from RGB to YIQ components. In this paper we show that color saturation, as well as luminance, can play an important role in achieving good image enhancement. The technique proposed is simple to implement and is based on the observation that the saturation component often contains high frequency components that are not present in the luminance component. Contrast and sharpness enhancement techniques are discussed; the computer processing algorithms are restricted to those that preserve the natural appearance of the scene. We also discuss limitations to luminance and saturation processing caused by poor quantization of the RGB tristimulus images.
Robin N. Strickland,
William F. McDonnell,
"Digital Color Image Enhancement Based On The Saturation Component," Optical Engineering 26(7), 267609 (1 July 1987). https://doi.org/10.1117/12.7974125