Image Processing Toolbox User's Guide

Converting Color Data Between Color Spaces

The Image Processing Toolbox represents colors as RGB values, either directly (in an RGB image) or indirectly (in an indexed image, where the colormap is stored in RGB format). However, there are other models besides RGB for representing colors numerically. The various models are referred to as color spaces because most of them can be mapped into a 2-D, 3-D, or 4-D coordinate system; thus, a color specification is made up of coordinates in a 2-D, 3-D, or 4-D space.

The various color spaces exist because they present color information in ways that make certain calculations more convenient or because they provide a way to identify colors that is more intuitive. For example, the RGB color space defines a color as the percentages of red, green, and blue hues mixed together. Other color models describe colors by their hue (green), saturation (dark green), and luminance, or intensity.

The toolbox supports these color spaces by providing a means for converting color data from one color space to another through a mathematical transformation.

This section

• Describes how to convert color data between these color spaces
• Describes how to perform color space conversions using ICC profiles
• Describes some toolbox functions for converting between the RGB color space and three commonly used color spaces: YIQ, HSV, and YCbCr

Dithering

Converting Between Device-Independent Color Spaces

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