A pragmatic approach to colour-table handling

A technique is defined for generating a representative subset of color space in a hue-saturation-intensity (HSI) coordinate system. The method is intended for use in color graphic data displays, where the colors must be chosen for maximum efficiency in the conveyance of information to the user. Modern displays offer a choice of 16 million colors, although only 256 can be used on-screen. The method consists of a transformation of the RGB axes to the HSI system by means of a polar coordinate mapping and axis rotation. The process is similar to the DIN Color System. The user selects the hue, saturation and brightness for each pixel of the monitor. Changes in the various parameters to indicate different data sets are performed non-uniformly in order to account for the variations in chromaticity perception by the user. The method described actually yields 1920 colors, from which 256 gray levels must be chosen for the display. The colors are all displayed on-screen and the designer employs a pointer device such as a mouse, trackball or a light pen to select colors for the display.