ABSTRACT
Color plays an important role in the study of images, and more generally in computer graphics. It will therefore occupy us for more than one chapter. Here we start to approach the subject by asking, What is color? What are the mathematical models for color? How should colors be discretized? As usual, our approach will be based on the four universes paradigm, as follows:
5.1 Color in the Physical Universe Color arises from electromagnetic radiation within a range of wavelengths that affect the human eye. The visible electromagnetic spectrum lies between the wavelengths of
λa = 400nm and λb = 800nm, approximately (the nanometer, abbreviated nm, is one billionth of a meter). Figure 5.1 shows the visible spectrum as a part of the much broader spectrum of all electromagnetic radiation, most of which is not visible. The energy associated with an electromagnetic wave is called radiant energy.
