TSL color space (
Tint
In color theory, a tint is a mixture of a color with white, which increases lightness, while a shade is a mixture with black, which increases darkness. Both processes affect the resulting color mixture's relative saturation. A tone is produc ...
,
Saturation
Saturation, saturated, unsaturation or unsaturated may refer to:
Chemistry
* Saturation, a property of organic compounds referring to carbon-carbon bonds
**Saturated and unsaturated compounds
** Degree of unsaturation
**Saturated fat or fatty aci ...
and
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 stan ...
) is a perceptual
color space
A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of colorwhether such representation entails an analog or a digital represent ...
which defines color as
tint
In color theory, a tint is a mixture of a color with white, which increases lightness, while a shade is a mixture with black, which increases darkness. Both processes affect the resulting color mixture's relative saturation. A tone is produc ...
(the degree to which a stimulus can be described as similar to or different from another stimuli that are described as
red
Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...
,
green
Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...
,
blue
Blue is one of the three primary colours in the RYB colour model (traditional colour theory), as well as in the RGB (additive) colour model. It lies between violet and cyan on the spectrum of visible light. The eye perceives blue when obs ...
,
yellow
Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the R ...
, and
white
White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White on ...
, can be thought of as
hue
In color theory, hue is one of the main properties (called Color appearance model#Color appearance parameters, color appearance parameters) of a color, defined technically in the CIECAM02 model as "the degree to which a Stimulus (physiology ...
with white added),
saturation
Saturation, saturated, unsaturation or unsaturated may refer to:
Chemistry
* Saturation, a property of organic compounds referring to carbon-carbon bonds
**Saturated and unsaturated compounds
** Degree of unsaturation
**Saturated fat or fatty aci ...
(the
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 ...
of a stimulus relative to its own
brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. The perception is not linear to luminance, ...
), and
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 stan ...
(the brightness of a stimulus relative to a stimulus that appears white in similar viewing conditions). Proposed by
Jean-Christophe Terrillon and
Shigeru Akamatsu,
TSL color space was developed primarily for the purpose of
face detection
Face detection is a computer technology being used in a variety of applications that identifies human faces in digital images. Face detection also refers to the psychological process by which humans locate and attend to faces in a visual scene. ...
.
Conversion between RGB and TSL
The conversion from gamma-corrected
RGB
The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three additiv ...
values to TSL is straightforward:
[
where:
Likewise, the reverse transform is as follows:
where:
For = 0, conversion from TSL to RGB is not unique because the sign of is lost in this case (note ±). In practice you can work this around by using ]signed zero
Signed zero is zero with an associated sign. In ordinary arithmetic, the number 0 does not have a sign, so that −0, +0 and 0 are identical. However, in computing, some number representations allow for the existence of two zeros, often denoted by ...
for and thus preserving the sign of .
Advantages of TSL
The advantages of TSL color space lie within the normalization within the RGB-TSL transform. Utilizing normalized r and g allows for chrominance spaces TSL to be more efficient for skin color segmentation. Additionally with this normalization, the sensitivity of the chrominance distributions to the variability of skin color is significantly reduced, allowing for an easier detection of different skin tones.
Comparison of TSL to other color spaces
Terrillon investigated the efficiency of facial detection for several different color spaces. Testing consisted of using the same algorithm with 10 different color spaces to detect faces in 90 images with 133 faces and 59 subjects - 27 Asian, 31 Caucasian, and 1 African). TSL showed superior performance to the other spaces, with 90.8% correct detection and 84.9% correct rejection. A full comparison can be seen in the table below.[
]
Disadvantages of TSL
TSL space could be made more efficient and robust. There currently exists no color correction algorithms for different camera systems. Additionally, despite a better accuracy of skin tone detection, detecting dark skin color still proves to be a challenge.[
]
Applications
Being a relatively new color space and having very specific uses, TSL hasn’t been widely implemented. Again, it is only very useful in skin detection algorithms. Skin detection itself can be used for a variety of applications – face detection, person tracking (for surveillance
Surveillance is the monitoring of behavior, many activities, or information for the purpose of information gathering, influencing, managing or directing. This can include observation from a distance by means of electronic equipment, such as c ...
and cinematographic purposes), and pornography
Pornography (often shortened to porn or porno) is the portrayal of sexual subject matter for the exclusive purpose of sexual arousal. Primarily intended for adults, filtering are a few examples. A Self-Organizing Map
A self-organizing map (SOM) or self-organizing feature map (SOFM) is an unsupervised machine learning technique used to produce a low-dimensional (typically two-dimensional) representation of a higher dimensional data set while preserving the to ...
(SOM) was implemented in skin detection using TSL and achieved comparable results to older methods of histograms
A histogram is an approximate representation of the frequency distribution, distribution of numerical data. The term was first introduced by Karl Pearson. To construct a histogram, the first step is to "Data binning, bin" (or "Data binning, buck ...
and Gaussian mixture models
In statistics, a mixture model is a probabilistic model for representing the presence of subpopulations within an overall population, without requiring that an observed data set should identify the sub-population to which an individual observation ...
.
See also
* HSL and HSV
HSL (for hue, saturation, lightness) and HSV (for hue, saturation, value; also known as HSB, for hue, saturation, brightness) are alternative representations of the RGB color model, RGB color model, designed in the 1970s by computer graphics res ...
* Face detection
Face detection is a computer technology being used in a variety of applications that identifies human faces in digital images. Face detection also refers to the psychological process by which humans locate and attend to faces in a visual scene. ...
* List of color spaces and their uses
References
{{DEFAULTSORT:Tsl Color Space
Color space