HCL (
hue–
chroma–
luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls wit ...
) or LCh refers to any of the many
cylindrical color space models that are designed to accord with human perception of color with the three parameters. Lch has been adopted by
information visualization
Data and information visualization (data viz/vis or info viz/vis) is the practice of designing and creating Graphics, graphic or visual Representation (arts), representations of a large amount of complex quantitative and qualitative data and i ...
practitioners to present data without the bias implicit in using varying
saturation.
They are, in general, designed to have characteristics of both cylindrical translations of the
RGB color space, such as
HSL and HSV
HSL and HSV are the two most common cylindrical coordinate system, cylindrical-coordinate representations of points in an RGB color model. The two representations rearrange the geometry of RGB in an attempt to be more intuitive and color vision, ...
, and the
L*a*b* color space.
Derivation
Color-making attributes
HCL concerns the following attributes of color appearance:
;
Hue: The "attribute of a visual sensation according to which an area appears to be similar to one of the
perceived colors: red, yellow, green, and blue, or to a combination of two of them".
[Fairchild (2005)]
/ref>
; Lightness
Lightness is a visual perception of the luminance (L) of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a stand ...
, value: The "brightness relative to the brightness of a similarly illuminated white".[
; ]Luminance
Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through, is emitted from, or is reflected from a particular area, and falls wit ...
(''Y'' or ''L''v,Ω): The radiance weighted by the effect of each wavelength on a typical human observer, measured in SI units in candela per square meter
The candela per square metre (symbol: cd/m2) is the unit of luminance in the International System of Units (SI). The unit is based on the candela, the SI unit of luminous intensity, and the square metre, the SI unit of area.
The nit (symbol: nt ...
(). Often the term ''luminance'' is used for the relative luminance
Relative luminance Y follows the Luminance, photometric definition of luminance L including spectral weighting for human vision, but while luminance L is a measure of light in units such as cd/m^2, relative luminance Y values are normalized as ...
, ''Y''/''Y''''n'', where ''Y''''n'' is the luminance of the reference white point.
; Colorfulness
Colorfulness, chroma and saturation are attributes of perceived color relating to chromatic intensity. As defined formally by the International Commission on Illumination (CIE) they respectively describe three different aspects of chromatic ...
: The "attribute of a visual sensation according to which the perceived color of an area appears to be more or less chromatic".[
The HSL and HSV color spaces are more intuitive translations of the RGB color space, because they provide a single hue number. However, their luminance variation does not match the way humans perceive color. Perceptually uniform color spaces outperform RGB in cases such as high noise environments.
]
CIE color spaces
CIE-based LCh color spaces are transformations of the two chroma values (ab or uv) into the polar coordinate. The source color spaces are still very well-regarded for their uniformity, and the transformation does not cause degradation in this aspect.
Sarifuddin, 2005
Sarifuddin, noting the lack of blue hue consistency of CIELAB—a common complaint among its users—
Abstractlong-form corrected report
/ref>
Other color appearance models
In general, any color appearance model
A color appearance model (CAM) is a mathematical model that seeks to describe the perceptual aspects of human color vision, i.e. viewing conditions under which the appearance of a color does not tally with the corresponding physical measurement ...
with a lightness and two chroma components can also be transformed into a HCL-type color space by turning the chroma components into polar coordinates.
References
External links
HCL Wizard online color apps
colorspace: HCL-Based Color Tools and Palettes in R
Generating random colors
How To Avoid Equidistant HSV Colors
{{color space, state=expanded
Color space