When gray level images are not sufficient to solve your image processing problem, and chromaticity characteristics such as hue and saturation might help, color processing allows you to process and analyze three components of a true color image at the same time.

Color images usually are designated as RGB, HLS, or YIQ format. An RGB image is composed of three components, the red, green and blue channels.

RGB

Although the RGB basis is good for acquisition and display of color images, it is not always a good basis to explain the perception of colors.

HLS

An HLS image is composed of components expressing the hue, luminance and saturation. Hue refers to the color (red, orange, yellow, green, blue, purple). Saturation measures the lack of whiteness in a color ("fire engine" is satured red and pink is desatured). Luminance is an intensity measure and allows you to distinguish between light and dark.

YIQ

The YIQ format is used largely in broadcasting. The advantage of YIQ images is that the brightness component Y can be used alone by monochrome receivers, while still spanning the color space with the chromatic components I and Q. In YIQ, the rgb basis is obtained by normalizing the RGB components so that . It removes intensity information, making it easier to localize an area based on chromaticity or saturation information.

Color Functions

Most of the functions that works on gray level images will work on color images. The process is performed three times, once on each component. Be aware that YIQ images are floating point images.