The HSI color space

The HIS color space is very important and attractive color model for image processing applications because it represents color s similarly how the human eye senses colors.

The HIS color model represents every color with three components: hue ( H ), saturation ( S ), intensity ( I ). The below figure illustrates how the HIS color space represents colors.

Description: HSIgraph

The Hue component describes the color itself in the form of an angle between [0,360] degrees. 0 degree mean red, 120 means green 240 means blue. 60 degrees is yellow, 300 degrees is magenta.
The Stauration component signals how much the color is polluted with white color. The range of the S component is [0,1].

The Intensity range is between [0,1] and 0 means black, 1 means white.

As the above figure shows, hue is more meaningfull when saturation approaches 1 and less meaningfull when saturation approaches 0 or when intensity approaches 0 or 1. Intensity also limits the saturation values.

To formula that converts from RGB to HSI or back is more complicated than with other color models, therefore we will not elaborate on the detailed specifics involved in this process.