huecomponent

The hue component is a fundamental part of several perceptual color models, such as HSV (also known as HSB) and HSL. It encodes the type or family of color on a circular color wheel, representing where the color lies between red, yellow, green, cyan, blue, and magenta. Hue is typically expressed as an angle, usually in degrees from 0 to 360, where 0 or 360 corresponds to red, 60 to yellow, 120 to green, 180 to cyan, 240 to blue, and 300 to magenta. Some implementations use a normalized range from 0 to 1.

Hue is not directly observable in the RGB color space; it is derived when converting RGB values to HSV or HSL. The conversion considers the maximum and minimum of the red, green, and blue components. If all three components are equal, the color is a shade of gray and the hue is undefined. Otherwise, the hue is computed from which component is the maximum and the relative differences among the components, yielding an angle on the color wheel that places the color in the appropriate sector. Different variants of the model define the exact calculation, but all aim to map a color to a single angular hue value while separately representing saturation and lightness or value.

Applications of the hue component include color-based segmentation, tracking, sorting, and manipulation in imaging and graphics. Hue is relatively stable with respect to changes in brightness, but it can be affected by lighting, shading, and saturation. In practice, hue is often used in combination with saturation and lightness or value to achieve robust color analysis, with awareness of potential ambiguities when colors are desaturated or display under varying illumination.