The Taming of the Hue, Saturation and Brightness Colour Space

The transformation of the RGB colour space to a hue, saturation and brightness colour space is essentially a conversion from a rectangular coordinate system to a cylindrical coordinate system. Nevertheless, a bewildering array of such conversions exist. We show that one of the main reasons for this is the dependence of the saturation values on the choice of the brightness function, and suggest a definition of saturation which is independent of the brightness. The usual ways of calculating brightness and hue are reviewed. Lastly, we examine some of the characteristics of the cylindrical colour coordinates and give a simple example in which the suggested cylindrical colour coordinates are used.