HLS color space
The HLS color space, also called HSL or HSI, stands for Hue, Saturation, Lightness (also Luminance or Luminosity) / Intensity. While HSV (Hue, Saturation, Value) can be viewed graphically as a color cone or hexcone, HSL is drawn as a double cone or double hexcone. Both systems are non-linear deformations of the RGB colour cube. The two apexes of the HLS double hexcone correspond to black and white. The angular parameter corresponds to hue, distance from the axis corresponds to saturation, and distance along the black-white axis corresponds to lightness.
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Converting from RGB
Both the HSL color space and the HSV color space have a common definition of hue, but not saturation and lightness/value.
HSL:
| <math>saturation<math> | <math>= \max \{R,G,B\} – \min \{R,G,B\}<math> |
| <math>lightness<math> | <math>= \frac{\max \{R,G,B\} + \min \{R,G,B\}}{2}<math> |
HSV:
| <math>saturation<math> | <math>= \frac{\max\{R,G,B\} – \min\{R,G,B\}}{\max\{R,G,B\}}<math> |
| <math>value<math> | <math>= \max \{R,G,B\}<math> |
Comparison of HSL and HSV
HSL is similar to HSV but better reflects the intuitive notion of "saturation" and "lightness"as two independent parameters, and is therefore more suitable for use by artists. The CSS3 specification from the W3C states, "Advantages of HSL are that it is symmetrical to lightness and darkness (which is not the case with HSV for example)..." This means that:
- In HSL, the Saturation component always goes from fully saturated color to the equivalent gray (in HSV, with V at maximum, it goes from saturated color to white, which may be considered counterintuitive).
- The Lightness in HSL always spans the entire range from black through the chosen hue to white (in HSV, the V component only goes half that way, from black to the chosen hue).
In software, a hue-based color model (HSV or HSL) is usually presented to the user in the form of a linear or circular hue chooser and a two-dimensional area (usually a square or a triangle) where you can choose saturation and value/lightness for the selected hue. With this representation, the difference between HSV or HSL is irrelevant. However, many programs also let you select a color via linear sliders or numeric entry fields, and for those controls, usually either HSL or HSV (not both) are used. HSV is traditionally more common. Here are some examples:
- Applications that use HSV (HSB):
- Adobe graphic applications (Illustrator, Photoshop, and others)
- The GIMP
- Apple Mac OS X system color picker (has a color disk for H/S and a slider for V)
- Xara X
- Applications that use HSL:
- Inkscape (starting from version 0.42)
- Paint Shop Pro
- Windows system color picker
- The CSS3 specification
Examples
| RGB | HSL | HSV | Result |
| (1, 0, 0) | (0°, 1, 0.5) | (0°, 1, 1) | |
| (0.5, 1, 0.5) | (120°, 0.5, 0.75) | (120°, 0.5, 1) | |
| (0, 0, 0.5) | (240°, 0.5, 0.25) | (240°, 1, 0.5) |
See also
- Color space:
- RGB color model commonly used for color monitors
- CMYK color model for color printing
- HSV color space
- HLS color space
- RYB color model the traditional color model used by artists.
- YUV for PAL television
- YIQ for NTSC television
External links
- An explanation of HSL and how it differs from RGB can be found in the W3C's CSS3 Color Module.
- Formulas for converting to and from RGB can be found on EasyRGB.com.
- Models color space HLS, HSI
Categories: Color space