In computer graphics several different mathematical systems exists which are used to describe colors. The colors system used in computer graphics are typically known as primary 3 color system. Primary colors are those which cannot be created by mixing other colors. With such system a color is defined by specifying an ordered set of 3 values. Composite colors are created by mixing varying amount of 3 primary colors which results in the creation of new color.
Two categories of color display techniques are:
1. Additive color system:
Colors in additive systems are created by adding colors to black to create new colors. The more color that is added to the black tends towards white. The presence of all the primary colors in sufficient amount creates pure white while the absence of all the primary colors creates pure black. Additive colors environments are self-luminous. For example, an image displayed on the screen uses additive color system.
2. Subtractive color system:
The subtractive color system is opposite of additive color system. Conceptually primary colors are subtracted from white to create new colors. The more colors that are subtracted tend towards black. Thus the presence of all primary colors creates pure black.
In computer graphics the following color systems are widely used:
(i) RGB – Red, Green, Blue
RGB color system is widely used in color systems for images formats nowadays. It is an additive color system in which different amounts of the color are added to black to produce new colors. The graphics format which follows the RGB color system uses a combination of 3 digits to represents a color instance. This 3 digit combination is representation is known as triplet.
0 0 0 ------- Black
1 1 2
2 2 2
| | |
255 255 255 ---- White
(ii) CMY – Cyan, Magenta, Yellow
CMY is a subtractive color system used by printers and photographers for the color with ink and emulsion normally on a white surface. It is used by most hard copy devices that deposit the color on white paper such as laser and inkjet printers.
(iii) HSV – Hue, Saturation, Value
HSV color system is one of many color system that vary the degree of properties of colors to create new colors, rather than using a mixture of the colors themselves. Here the hue color specifies the common use of colors such as red, orange, etc. The saturation refers to the amount of white in a hue and the value is called brightness. So the HSV is also called as HSB where H is hue, S is saturation and B is brightness.
(iv) HLS – Hue, Lightness, Saturation
The HLS color system is closely related to HSV and behaves in the same way. There are several other color systems that are similar to HSV in that they create color by altering hue with 2 other values. That includes: