Color Spaces

Color spaces allow you to represent a color. A color space is a subspace within a three-dimensional coordinate system where each color is represented by a point. You can use color spaces to facilitate the description of colors between persons, machines, or software programs.

Various industries and applications use a number of different color spaces. Humans perceive color according to parameters such as brightness, hue, and intensity, while computers perceive color as a combination of red, green, and blue. The printing industry uses cyan, magenta, and yellow to specify color.

The following is a list of common color spaces:

• RGB—Based on red, green, and blue. Used by computers to display images.
• HSL—Based on hue, saturation, and luminance. Used in image processing applications.
• CIE—Based on brightness, hue, and colorfulness. Defined by the Commission Internationale de l'Eclairage (International Commission on Illumination) as the different sensations of color that the human brain perceives.
• CMY—Based on cyan, magenta, and yellow. Used by the printing industry.
• YIQ—Separates the luminance information (Y) from the color information (I and Q). Used for TV broadcasting.

When to Use

You must define a color space every time you process color images. If you expect the lighting conditions to vary considerably during your color machine vision application, use the HSL color space. The HSL color space provides more accurate color information than the RGB space when running color processing functions, such as color matching, color location, and color pattern matching.

If you do not expect the lighting conditions to vary considerably during your application, and you can easily define the colors you are looking for using red, green, and blue, use the RGB space. Also, use the RGB space if you want to display, but not process, color images in your application. The RGB space reproduces an image as you would expect to see it.