The basic function of digital color encoding in imaging systems is to provide a digital representation of colors for image processing, storage, and interchange among systems. Within a given system, encoding provides a digital link between the system's inputs and outputs.
In a simple system, having just one type of input and one type of output, color encoding can be performed prior to any signal processing (Figure 9.1). The encoding therefore is a direct representation of the color values measured by the system's input device.
In more complex systems, supporting multiple types of inputs and outputs, such an arrangement is impractical because each and every combination of input and output would require a separate signal processing transform. For example, a single output device would require two different transforms in order to process color values measured by one input device that scans photographic negative films and another that scans reflection prints. The number of required system transforms in this arrangement equals the product of the number of inputs and outputs. That can get to be a sizable number of transforms. A system having four inputs and eight outputs, for example, would require 32 different transforms (Figure 9.2).
A much more efficient system results if the color signal processing is split into two parts: input signal processing and output signal processing. In this arrangement, shown in Figure 9.3, each input and each output has only a single ...