There are some special terms which are widely used in color theory or in color processing.Some of them are explained here:-
1)Colorfulness:- Colorfulness is the degree of difference between a color & gray.
In other words "The attribute of a visual sensation according to which the perceived color of an area appears to be more or less chromatic ".
2)Chroma:-Chroma is the colorfulness relative to the brightness of another color that appears white under similar viewing conditions.
In other words "the colorfulness relative to the brightness of a similarly illuminated white".
C= M-m
where
M=Max(R,G,B)
m=min(R,G,B)
3)Saturation:-Saturation is the colorfulness of a color relative to its own brightness.Saturation for the HSV,HSL and HSI can be calculate by following formulas:-
4)Lightness:-Lightness is a property of a color or a dimension of a color space that is defined in a way to reflect the subjective brightness perception of a color for humans along a lightness-darkness axis.
In other words "the brightness relative to the brightness of a similarly illuminated white."
In the HSL model lightness is defined by the average of largest and smallest color components.
L=1/2(M+m)
where
M=Max(R,G,B)
m=min(R,G,B)
5)Brightness:-Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.In the RGB color space ,brightness can be thought of as arithmetic mean of RGB value.
Brightness is also a color co-ordinates in HSB or HSV color space.It is denoted by B.It is also called value.
In other words "the attributes of a visual sensation according to which an area appears to omit more or less light".In the HSV color model value is defined as largest component of color.
V = M
where
M=Max(R,G,B)
6)Luma:-Luma represents the brightness in an image.This term is used in color video.Basically luma is the weighted sum of gamma compressed R'G'B' color components of color video.Luma is denoted by Y'.The prime symbol (') denotes gamma compression.For the Rec 709 primaries used in sRGB
Y'709=0.21R+0.72G+0.07B
For the Rec. 601 NTSC primaries
Y'601=0.30R+0.59G+0.11B
7)Luminance:-Luminance is the 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 or is omitted thruogh a particular area
& falls within a given solid angle.It is denoted by Y.The SI unit for luminance is candela/Square metre.Here is the formula for luminance:-
is the luminance (cd/m2),
is the luminous flux or luminous power (lm),
is the angle between the surface normal and the specified direction,
is the area of the surface (m2), and
is the solid angle (sr).
8)Luminosity:-Luminosity is generally understood by measurement of brightness.It has SI unit joules per second which is called watt.Here is the formula for luminosity of a star:-
9)Hue:- Hue is one of the main properties of a color.It is also a color co-ordinates in HSV or HSB .The angle around the central vertical axis corresponds hue.A hue is the color element of color wheel.
In other words "the attributes of visual sensation according to which an area appears to be similar to one of the perceived colors : red,yellow.green & blue or to a combination of two of them".
The hue is the proportion of the distance around the edge of the edge of the hexagon which passes through the projected point.Typically, it is measured in degrees and denoted by H.
10)Contrast:-Contrast is the difference between the luminance and/or color that makes an object distinguishable.In visual perception of the real world ,contrast is determined by the difference in the color & brightness of the object & other objects within the same field of view. Contrast is also the difference between the color or shading of the printed material on a document & the background on which it is printed.Contrast is the ratio of luminance & average luminance.
11)Intensity:-The total amount of light passing through a area is called intensity.It is denoted by I.It is also called radiance.In the HSI model intensity is the average of three color component:-
I=1/3(R+G+B)
1)Colorfulness:- Colorfulness is the degree of difference between a color & gray.
In other words "The attribute of a visual sensation according to which the perceived color of an area appears to be more or less chromatic ".
2)Chroma:-Chroma is the colorfulness relative to the brightness of another color that appears white under similar viewing conditions.
In other words "the colorfulness relative to the brightness of a similarly illuminated white".
C= M-m
where
M=Max(R,G,B)
m=min(R,G,B)
3)Saturation:-Saturation is the colorfulness of a color relative to its own brightness.Saturation for the HSV,HSL and HSI can be calculate by following formulas:-
4)Lightness:-Lightness is a property of a color or a dimension of a color space that is defined in a way to reflect the subjective brightness perception of a color for humans along a lightness-darkness axis.
In other words "the brightness relative to the brightness of a similarly illuminated white."
In the HSL model lightness is defined by the average of largest and smallest color components.
L=1/2(M+m)
where
M=Max(R,G,B)
m=min(R,G,B)
5)Brightness:-Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light.In the RGB color space ,brightness can be thought of as arithmetic mean of RGB value.
Brightness is also a color co-ordinates in HSB or HSV color space.It is denoted by B.It is also called value.
In other words "the attributes of a visual sensation according to which an area appears to omit more or less light".In the HSV color model value is defined as largest component of color.
V = M
where
M=Max(R,G,B)
6)Luma:-Luma represents the brightness in an image.This term is used in color video.Basically luma is the weighted sum of gamma compressed R'G'B' color components of color video.Luma is denoted by Y'.The prime symbol (') denotes gamma compression.For the Rec 709 primaries used in sRGB
Y'709=0.21R+0.72G+0.07B
For the Rec. 601 NTSC primaries
Y'601=0.30R+0.59G+0.11B
7)Luminance:-Luminance is the 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 or is omitted thruogh a particular area
& falls within a given solid angle.It is denoted by Y.The SI unit for luminance is candela/Square metre.Here is the formula for luminance:-
is the luminance (cd/m2), is the luminous flux or luminous power (lm), is the angle between the surface normal and the specified direction, is the area of the surface (m2), and is the solid angle (sr).8)Luminosity:-Luminosity is generally understood by measurement of brightness.It has SI unit joules per second which is called watt.Here is the formula for luminosity of a star:-
where
- σ is the Stefan–Boltzmann constant 5.67×10−8 W·m-2·K-4.
In other words "the attributes of visual sensation according to which an area appears to be similar to one of the perceived colors : red,yellow.green & blue or to a combination of two of them".
The hue is the proportion of the distance around the edge of the edge of the hexagon which passes through the projected point.Typically, it is measured in degrees and denoted by H.
11)Intensity:-The total amount of light passing through a area is called intensity.It is denoted by I.It is also called radiance.In the HSI model intensity is the average of three color component:-
I=1/3(R+G+B)
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