Describing Color
Color can be described in terms of components. The components most often used by imaging professionals are hue, saturation, and brightness. A hue is what we normally think of as a color. A color's hue fixes its place in the visible spectrum of light. The saturation of a color is how "pure" or "strong" a color is. Neutral gray is said to have zero saturation. The brightness of a color refers to the intensity of light that is reflected or transmitted by an image.
The terms tint, tone, and shade are also well-used in color imaging literature. A tint of a color is obtained by mixing its hue with white. A tone of a color is created by mixing a hue with gray. A shade of a color is made by adding black to its hue.
Color Spaces
The human eye is often able to detect many more colors than digital devices can reproduce. For instance, if you look at a blank, white page of paper, your eye is probably detecting at least 100 distinct shades of white. A white wall can easily have 1500 shades of white.
High-quality digital cameras, scanners, and other image acquisition devices can also detect hundreds of thousands or even millions of colors. Because of the presence of so many detectable colors, imaging professionals have invented models for specifying colors. These models are called color spaces.
The reason these models are referred to as color spaces is that most of them can be mapped into a 2-D, 3-D, or 4-D coordinate system similar to a Cartesian coordinate system. Hence colors can be said to be composed of coordinates in a 2-D, 3-D, or 4-D space. The color components in a color space are also referred to as color channels.
Some color spaces are intended to be independent of any device that is used to produce color images. Some are very device dependent. Both device-dependent and device-independent color spaces are discussed in the following sections:
- RGB Color Spaces
- HSV Color Spaces
- HLS Color Spaces
- CMY and CMYK Color Spaces
- Device-Dependent Color Spaces
- Device-Independent Color Spaces
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