HSL and HSV are the two most common cylindrical-coordinate representations of points in an RGB color model. Developed in the 1970s for computer graphics applications, HSL and HSV are used today in color pickers, in image editing software, and less commonly in image analysis and computer vision.
The two representations rearrange the geometry of RGB in an attempt to be more intuitive and perceptually relevant than the cartesian (cube) representation, by mapping the values into a cylinder loosely inspired by a traditional color wheel. The angle around the central vertical axis corresponds to “hue” and the distance from the axis corresponds to “saturation“. These first two values give the two schemes the ‘H’ and ‘S’ in their names. The height corresponds to a third value, the system’s representation of the perceived luminance in relation to the saturation.
Perceived luminance is a notoriously difficult aspect of color to represent in a digital format (see disadvantages section), and this has given rise to two systems attempting to solve this issue: HSL (L for lightness) and HSV or HSB (V for value or B for brightness). A third model, HSI (I for intensity), common in computer vision applications, attempts to balance the advantages and disadvantages of the other two systems. While typically consistent, these definitions are not standardized, and the abbreviations are colloquially interchangeable for any of these three or several other related cylindrical models. Note also that while “hue” in HSL and HSV refers to the same attribute, their definitions of “saturation” differ dramatically. (For technical definitions of these terms, see Color-making attributes.)
Both of these representations are used widely in computer graphics, but both are also criticized for not adequately separating color-making attributes, and for their lack of perceptual uniformity. This means that the color displayed on one monitor for a given HSV value is unlikely to exactly match the color seen on another monitor unless the two are precisely adjusted to absolute color spaces.
Other, more computationally intensive models, such as CIELAB or CIECAM02 are said to better achieve the goal of accurate and uniform color display, but their adoption has been slow. HSL and HSV were widely adopted as a standard alternative to RGB in the early days of color computers due to their low processing time requirements, and their similarity to traditional artist’s color theory. Even in the case of digital artists, who generally come to recognize the flaws of HSL/HSB systems fairly quickly, it is simpler to learn to work around the flaws of a familiar system of color representation than to relearn their entire way of thinking about color by adapting to the less intuitive RGB system of color mixing. Thus, in spite of their flaws, HSL and HSV have proven difficult to replace.
Contents [hide]
- 1 Basic principle
- 2 Motivation
- 3 Formal derivation
- 1 Color-making attributes
- 2 General approach
- 3 Hue and chroma
- 4 Lightness
- 5 Saturation
- 6 Examples
- 4 Use in end-user software
- 5 Use in image analysis
- 6 Disadvantages
- 7 Other cylindrical-coordinate color models
- 8 Converting to RGB
- 1 From HSV
- 2 From HSL
- 3 From luma/chroma/hue
- 9 Swatches
- 1 HSV (Hue Saturation Value)
- 2 HSL
- 10 Notes and references
- 11 Bibliography
- 12 External links