内容提纲：
XYZ ⇆ Standard-RGB XYZ ⇆ Adobe-RGB
XYZ ⇆ Yxy XYZ ⇆ Hunter-Lab
XYZ ⇆ CIE-L*ab CIE-L*ab ⇆ CIE-L*CH°
XYZ ⇆ CIE-L*uv RGB ⇆ HSL
RGB ⇆ HSV RGB ⇆ CMY
CMY ⇆ CMYK XYZ (Tristimulus)
Delta C* Delta H* Delta E* CIE
Delta E1994 Delta E2000 Delta CMC
RGB ⇆ YUV
进行图形图像处理时，我们经常会遇到颜色转换的问题，这里列出了常见的颜色转换公式，基本上称得上“大全”了。
1、XYZ → Standard-RGB
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//X, Y and Z input refer to a D65/2° standard illuminant.
//sR, sG and sB (standard RGB) output range = 0 ÷ 255
var_X = X / 100
var_Y = Y / 100
var_Z = Z / 100
var_R = var_X * 3.2406 + var_Y * -1.5372 + var_Z * -0.4986
var_G = var_X * -0.9689 + var_Y * 1.8758 + var_Z * 0.0415
var_B = var_X * 0.0557 + var_Y * -0.2040 + var_Z * 1.0570
if ( var_R > 0.0031308 ) var_R = 1.055 * ( var_R ^ ( 1 / 2.4 ) ) - 0.055
else var_R = 12.92 * var_R
if ( var_G > 0.0031308 ) var_G = 1.055 * ( var_G ^ ( 1 / 2.4 ) ) - 0.055
else var_G = 12.92 * var_G
if ( var_B > 0.0031308 ) var_B = 1.055 * ( var_B ^ ( 1 / 2.4 ) ) - 0.055
else var_B = 12.92 * var_B
sR = var_R * 255
sG = var_G * 255
sB = var_B * 255
2、Standard-RGB → XYZ
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//sR, sG and sB (Standard RGB) input range = 0 ÷ 255
//X, Y and Z output refer to a D65/2° standard illuminant.
var_R = ( sR / 255 )
var_G = ( sG / 255 )
var_B = ( sB / 255 )
if ( var_R > 0.04045 ) var_R = ( ( var_R + 0.055 ) / 1.055 ) ^ 2.4
else var_R = var_R / 12.92
if ( var_G > 0.04045 ) var_G = ( ( var_G + 0.055 ) / 1.055 ) ^ 2.4
else var_G = var_G / 12.92
if ( var_B > 0.04045 ) var_B = ( ( var_B + 0.055 ) / 1.055 ) ^ 2.4
else var_B = var_B / 12.92
var_R = var_R * 100
var_G = var_G * 100
var_B = var_B * 100
X = var_R * 0.4124 + var_G * 0.3576 + var_B * 0.1805
Y = var_R * 0.2126 + var_G * 0.7152 + var_B * 0.0722
Z = var_R * 0.0193 + var_G * 0.1192 + var_B * 0.9505
3、XYZ → Adobe-RGB
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//X, Y and Z input refer to a D65/2° standard illuminant.
//aR, aG and aB (RGB Adobe 1998) output range = 0 ÷ 255
var_X = X / 100
var_Y = Y / 100
var_Z = Z / 100
var_R = var_X * 2.04137 + var_Y * -0.56495 + var_Z * -0.34469
var_G = var_X * -0.96927 + var_Y * 1.87601 + var_Z * 0.04156
var_B = var_X * 0.01345 + var_Y * -0.11839 + var_Z * 1.01541
var_R = var_R ^ ( 1 / 2.19921875 )
var_G = var_G ^ ( 1 / 2.19921875 )
var_B = var_B ^ ( 1 / 2.19921875 )
aR = var_R * 255
aG = var_G * 255
aB = var_B * 255
4、Adobe-RGB → XYZ
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//aR, aG and aB (RGB Adobe 1998) input range = 0 ÷ 255
//X, Y and Z output refer to a D65/2° standard illuminant.
var_R = ( aR / 255 )
var_G = ( aG / 255 )
var_B = ( aB / 255 )
var_R = var_R ^ 2.19921875
var_G = var_G ^ 2.19921875
var_B = var_B ^ 2.19921875
var_R = var_R * 100
var_G = var_G * 100
var_B = var_B * 100
X = var_R * 0.57667 + var_G * 0.18555 + var_B * 0.18819
Y = var_R * 0.29738 + var_G * 0.62735 + var_B * 0.07527
Z = var_R * 0.02703 + var_G * 0.07069 + var_B * 0.99110
5、XYZ → Yxy
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Y = Y
x = X / ( X + Y + Z )
y = Y / ( X + Y + Z )
6、Yxy → XYZ
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X = x * ( Y / y )
Y = Y
Z = ( 1 - x - y ) * ( Y / y )
7、XYZ → Hunter-Lab
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//Reference-X, Y and Z refer to specific illuminants and observers.
//Common reference values are available below in this same page.
var_Ka = ( 175.0 / 198.04 ) * ( Reference-Y + Reference-X )
var_Kb = ( 70.0 / 218.11 ) * ( Reference-Y + Reference-Z )
Hunter-L = 100.0 * sqrt( Y / Reference-Y )
Hunter-a = var_Ka * ( ( ( X / Reference-X ) - ( Y / Reference-Y ) ) / sqrt( Y / Reference-Y ) )
Hunter-b = var_Kb * ( ( ( Y / Reference-Y ) - ( Z / Reference-Z ) ) / sqrt( Y / Reference-Y ) )
8、Hunter-Lab → XYZ
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//Reference-X, Y and Z refer to specific illuminants and observers.
//Common reference values are available below in this same page.
var_Ka = ( 175.0 / 198.04 ) * ( Reference-Y + Reference-X )
var_Kb = ( 70.0 / 218.11 ) * ( Reference-Y + Reference-Z )
Y = ( ( Hunter-L / Reference-Y ) ^ 2 ) * 100.0
X = ( Hunter-a / var_Ka * sqrt( Y / Reference-Y ) + ( Y / Reference-Y ) ) * Reference-X
Z = - ( Hunter-b / var_Kb * sqrt( Y / Reference-Y ) - ( Y / Reference-Y ) ) * Reference-Z
9、XYZ → CIE-L*ab
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//Reference-X, Y and Z refer to specific illuminants and observers.
//Common reference values are available below in this same page.
var_X = X / Reference-X
var_Y = Y / Reference-Y
var_Z = Z / Reference-Z
if ( var_X > 0.008856 ) var_X = var_X ^ ( 1/3 )
else var_X = ( 7.787 * var_X ) + ( 16 / 116 )
if ( var_Y > 0.008856 ) var_Y = var_Y ^ ( 1/3 )
else var_Y = ( 7.787 * var_Y ) + ( 16 / 116 )
if ( var_Z > 0.008856 ) var_Z = var_Z ^ ( 1/3 )
else var_Z = ( 7.787 * var_Z ) + ( 16 / 116 )
CIE-L* = ( 116 * var_Y ) - 16
CIE-a* = 500 * ( var_X - var_Y )
CIE-b* = 200 * ( var_Y - var_Z )
10、CIE-L*ab → XYZ
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//Reference-X, Y and Z refer to specific illuminants and observers.
//Common reference values are available below in this same page.
var_Y = ( CIE-L* + 16 ) / 116
var_X = CIE-a* / 500 + var_Y
var_Z = var_Y - CIE-b* / 200
if ( var_Y^3 > 0.008856 ) var_Y = var_Y^3
else var_Y = ( var_Y - 16 / 116 ) / 7.787
if ( var_X^3 > 0.008856 ) var_X = var_X^3
else var_X = ( var_X - 16 / 116 ) / 7.787
if ( var_Z^3 > 0.008856 ) var_Z = var_Z^3
else var_Z = ( var_Z - 16 / 116 ) / 7.787
X = var_X * Reference-X
Y = var_Y * Reference-Y
Z = var_Z * Reference-Z
11、CIE-L*ab → CIE-L*CH°
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var_H = arc_tangent( CIE-b*, CIE-a* ) //Quadrant by signs
if ( var_H > 0 ) var_H = ( var_H / PI ) * 180
else var_H = 360 - ( abs( var_H ) / PI ) * 180
CIE-L* = CIE-L*
CIE-C* = sqrt( CIE-a* ^ 2 + CIE-b* ^ 2 )
CIE-H° = var_H
12、CIE-L*CH° → CIE-L*ab
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//CIE-H° range = 0 ÷ 360°
CIE-L* = CIE-L*
CIE-a* = cos( degree_2_radian( CIE-H° ) ) * CIE-C*
CIE-b* = sin( degree_2_radian( CIE-H° ) ) * CIE-C*
13、XYZ → CIE-L*uv
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//Reference-X, Y and Z refer to specific illuminants and observers.
//Common reference values are available below in this same page.
var_U = ( 4 * X ) / ( X + ( 15 * Y ) + ( 3 * Z ) )
var_V = ( 9 * Y ) / ( X + ( 15 * Y ) + ( 3 * Z ) )
var_Y = Y / 100
if ( var_Y > 0.008856 ) var_Y = var_Y ^ ( 1/3 )
else var_Y = ( 7.787 * var_Y ) + ( 16 / 116 )
ref_U = ( 4 * Reference-X ) / ( Reference-X + ( 15 * Reference-Y ) + ( 3 * Reference-Z ) )
ref_V = ( 9 * Reference-Y ) / ( Reference-X + ( 15 * Reference-Y ) + ( 3 * Reference-Z ) )
CIE-L* = ( 116 * var_Y ) - 16
CIE-u* = 13 * CIE-L* * ( var_U - ref_U )
CIE-v* = 13 * CIE-L* * ( var_V - ref_V )
14、CIE-L*uv → XYZ
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//Reference-X, Y and Z refer to specific illuminants and observers.
//Common reference values are available below in this same page.
var_Y = ( CIE-L* + 16 ) /116
if ( var_Y^3 > 0.008856 ) var_Y = var_Y^3
else var_Y = ( var_Y - 16 / 116 ) / 7.787
ref_U = ( 4 * Reference-X ) / ( Reference-X + ( 15 * Reference-Y ) + ( 3 * Reference-Z ) )
ref_V = ( 9 * Reference-Y ) / ( Reference-X + ( 15 * Reference-Y ) + ( 3 * Reference-Z ) )
var_U = CIE-u* / ( 13 * CIE-L* ) + ref_U
var_V = CIE-v* / ( 13 * CIE-L* ) + ref_V
Y = var_Y * 100
X = - ( 9 * Y * var_U ) / ( ( var_U - 4 ) * var_V - var_U * var_V )
Z = ( 9 * Y - ( 15 * var_V * Y ) - ( var_V * X ) ) / ( 3 * var_V )
15、RGB → HSL
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//R, G and B input range = 0 ÷ 255
//H, S and L output range = 0 ÷ 1.0
var_R = ( R / 255 )
var_G = ( G / 255 )
var_B = ( B / 255 )
var_Min = min( var_R, var_G, var_B ) //Min. value of RGB
var_Max = max( var_R, var_G, var_B ) //Max. value of RGB
del_Max = var_Max - var_Min //Delta RGB value
L = ( var_Max + var_Min )/ 2
if ( del_Max == 0 ) //This is a gray, no chroma...
{
H = 0
S = 0
}
else //Chromatic data...
{
if ( L < 0.5 ) S = del_Max / ( var_Max + var_Min )
else S = del_Max / ( 2 - var_Max - var_Min )
del_R = ( ( ( var_Max - var_R ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_G = ( ( ( var_Max - var_G ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_B = ( ( ( var_Max - var_B ) / 6 ) + ( del_Max / 2 ) ) / del_Max
if ( var_R == var_Max ) H = del_B - del_G
else if ( var_G == var_Max ) H = ( 1 / 3 ) + del_R - del_B
else if ( var_B == var_Max ) H = ( 2 / 3 ) + del_G - del_R
if ( H < 0 ) H += 1
if ( H > 1 ) H -= 1
}
16、HSL → RGB
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//H, S and L input range = 0 ÷ 1.0
//R, G and B output range = 0 ÷ 255
if ( S == 0 )
{
R = L * 255
G = L * 255
B = L * 255
}
else
{
if ( L < 0.5 ) var_2 = L * ( 1 + S )
else var_2 = ( L + S ) - ( S * L )
var_1 = 2 * L - var_2
R = 255 * Hue_2_RGB( var_1, var_2, H + ( 1 / 3 ) )
G = 255 * Hue_2_RGB( var_1, var_2, H )
B = 255 * Hue_2_RGB( var_1, var_2, H - ( 1 / 3 ) )
}
Hue_2_RGB( v1, v2, vH ) //Function Hue_2_RGB
{
if ( vH < 0 ) vH += 1
if( vH > 1 ) vH -= 1
if ( ( 6 * vH ) < 1 ) return ( v1 + ( v2 - v1 ) * 6 * vH )
if ( ( 2 * vH ) < 1 ) return ( v2 )
if ( ( 3 * vH ) < 2 ) return ( v1 + ( v2 - v1 ) * ( ( 2 / 3 ) - vH ) * 6 )
return ( v1 )
}
17、RGB → HSV
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//R, G and B input range = 0 ÷ 255
//H, S and V output range = 0 ÷ 1.0
var_R = ( R / 255 )
var_G = ( G / 255 )
var_B = ( B / 255 )
var_Min = min( var_R, var_G, var_B ) //Min. value of RGB
var_Max = max( var_R, var_G, var_B ) //Max. value of RGB
del_Max = var_Max - var_Min //Delta RGB value
V = var_Max
if ( del_Max == 0 ) //This is a gray, no chroma...
{
H = 0
S = 0
}
else //Chromatic data...
{
S = del_Max / var_Max
del_R = ( ( ( var_Max - var_R ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_G = ( ( ( var_Max - var_G ) / 6 ) + ( del_Max / 2 ) ) / del_Max
del_B = ( ( ( var_Max - var_B ) / 6 ) + ( del_Max / 2 ) ) / del_Max
if ( var_R == var_Max ) H = del_B - del_G
else if ( var_G == var_Max ) H = ( 1 / 3 ) + del_R - del_B
else if ( var_B == var_Max ) H = ( 2 / 3 ) + del_G - del_R
if ( H < 0 ) H += 1
if ( H > 1 ) H -= 1
}
18、HSV → RGB
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//H, S and V input range = 0 ÷ 1.0
//R, G and B output range = 0 ÷ 255
if ( S == 0 )
{
R = V * 255
G = V * 255
B = V * 255
}
else
{
var_h = H * 6
if ( var_h == 6 ) var_h = 0 //H must be < 1
var_i = int( var_h ) //Or ... var_i = floor( var_h )
var_1 = V * ( 1 - S )
var_2 = V * ( 1 - S * ( var_h - var_i ) )
var_3 = V * ( 1 - S * ( 1 - ( var_h - var_i ) ) )
if ( var_i == 0 ) { var_r = V ; var_g = var_3 ; var_b = var_1 }
else if ( var_i == 1 ) { var_r = var_2 ; var_g = V ; var_b = var_1 }
else if ( var_i == 2 ) { var_r = var_1 ; var_g = V ; var_b = var_3 }
else if ( var_i == 3 ) { var_r = var_1 ; var_g = var_2 ; var_b = V }
else if ( var_i == 4 ) { var_r = var_3 ; var_g = var_1 ; var_b = V }
else { var_r = V ; var_g = var_1 ; var_b = var_2 }
R = var_r * 255
G = var_g * 255
B = var_b * 255
}
19、RGB → CMY
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//R, G and B input range = 0 ÷ 255
//C, M and Y output range = 0 ÷ 1.0
C = 1 - ( R / 255 )
M = 1 - ( G / 255 )
Y = 1 - ( B / 255 )
20、CMY → RGB
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//C, M and Y input range = 0 ÷ 1.0
//R, G and B output range = 0 ÷ 255
R = ( 1 - C ) * 255
G = ( 1 - M ) * 255
B = ( 1 - Y ) * 255
21、CMY → CMYK
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//C, M, Y and K range = 0 ÷ 1.0
var_K = 1
if ( C < var_K ) var_K = C
if ( M < var_K ) var_K = M
if ( Y < var_K ) var_K = Y
if ( var_K == 1 ) {
C = 0 //Black only
M = 0
Y = 0
}
else {
C = ( C - var_K ) / ( 1 - var_K )
M = ( M - var_K ) / ( 1 - var_K )
Y = ( Y - var_K ) / ( 1 - var_K )
}
K = var_K
22、CMYK → CMY
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//C, M, Y and K range = 0 ÷ 1.0
C = ( C * ( 1 - K ) + K )
M = ( M * ( 1 - K ) + K )
Y = ( Y * ( 1 - K ) + K )
23、XYZ (Tristimulus) Reference values of a perfect reflecting diffuser
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Observer 2° (CIE 1931) 10° (CIE 1964) Note
Illuminant X2 Y2 Z2 X10 Y10 Z10
A 109.850 100.000 35.585 111.144 100.000 35.200 Incandescent/tungsten
B 99.0927 100.000 85.313 99.178; 100.000 84.3493 Old direct sunlight at noon
C 98.074 100.000 118.232 97.285 100.000 116.145 Old daylight
D50 96.422 100.000 82.521 96.720 100.000 81.427 ICC profile PCS
D55 95.682 100.000 92.149 95.799 100.000 90.926 Mid-morning daylight
D65 95.047 100.000 108.883 94.811 100.000 107.304 Daylight, sRGB, Adobe-RGB
D75 94.972 100.000 122.638 94.416 100.000 120.641 North sky daylight
E 100.000 100.000 100.000 100.000 100.000 100.000 Equal energy
F1 92.834 100.000 103.665 94.791 100.000 103.191 Daylight Fluorescent
F2 99.187 100.000 67.395 103.280 100.000 69.026 Cool fluorescent
F3 103.754 100.000 49.861 108.968 100.000 51.965 White Fluorescent
F4 109.147 100.000 38.813 114.961 100.000 40.963 Warm White Fluorescent
F5 90.872 100.000 98.723 93.369 100.000 98.636 Daylight Fluorescent
F6 97.309 100.000 60.191 102.148 100.000 62.074 Lite White Fluorescent
F7 95.044 100.000 108.755 95.792 100.000 107.687 Daylight fluorescent, D65 simulator
F8 96.413 100.000 82.333 97.115 100.000 81.135 Sylvania F40, D50 simulator
F9 100.365 100.000 67.868 102.116 100.000 67.826 Cool White Fluorescent
F10 96.174 100.000 81.712 99.001 100.000 83.134 Ultralume 50, Philips TL85
F11 100.966 100.000 64.370 103.866 100.000 65.627 Ultralume 40, Philips TL84
F12 108.046 100.000 39.228 111.428 100.000 40.353 Ultralume 30, Philips TL83
These are formulas used to calculate color difference (Δ) in the CIE-L*ab and CIE-L*CH° spaces:
24、Delta C*
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CIE-a*1, CIE-b*1 //Color #1 CIE-L*ab values
CIE-a*2, CIE-b*2 //Color #2 CIE-L*ab values
Delta C* = sqrt( ( CIE-a*2 ^ 2 ) + ( CIE-b*2 ^ 2 ) )
- sqrt( ( CIE-a*1 ^ 2 ) + ( CIE-b*1 ^ 2 ) )
25、Delta H*
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CIE-a*1, CIE-b*1 //Color #1 CIE-L*ab values
CIE-a*2, CIE-b*2 //Color #2 CIE-L*ab values
xDE = sqrt( ( CIE-a*2 ^ 2 ) + ( CIE-b*2 ^ 2 ) )
- sqrt( ( CIE-a*1 ^ 2 ) + ( CIE-b*1 ^ 2 ) )
Delta H* = sqrt( ( CIE-a*2 - CIE-a*1 ) ^ 2
+ ( CIE-b*2 - CIE-b*1 ) ^ 2 - ( xDE ^ 2 ) )
26、Delta E* CIE
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CIE-L*1, CIE-a*1, CIE-b*1 //Color #1 CIE-L*ab values
CIE-L*2, CIE-a*2, CIE-b*2 //Color #2 CIE-L*ab values
Delta E* = sqrt( ( ( CIE-L*1 - CIE-L*2 ) ^ 2 )
+ ( ( CIE-a*1 - CIE-a*2 ) ^ 2 )
+ ( ( CIE-b*1 - CIE-b*2 ) ^ 2 ) )
27、Delta E1994
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CIE-L*1, CIE-a*1, CIE-b*1 //Color #1 CIE-L*ab values
CIE-L*2, CIE-a*2, CIE-b*2 //Color #2 CIE-L*ab values
WHT-L, WHT-C, WHT-H //Weighting factors
xC1 = sqrt( ( CIE-a*1 ^ 2 ) + ( CIE-b*1 ^ 2 ) )
xC2 = sqrt( ( CIE-a*2 ^ 2 ) + ( CIE-b*2 ^ 2 ) )
xDL = CIE-L*2 - CIE-L*1
xDC = xC2 - xC1
xDE = sqrt( ( ( CIE-L*1 - CIE-L*2 ) * ( CIE-L*1 - CIE-L*2 ) )
+ ( ( CIE-a*1 - CIE-a*2 ) * ( CIE-a*1 - CIE-a*2 ) )
+ ( ( CIE-b*1 - CIE-b*2 ) * ( CIE-b*1 - CIE-b*2 ) ) )
xDH = ( xDE * xDE ) - ( xDL * xDL ) - ( xDC * xDC )
if ( xDH > 0 )
{
xDH = sqrt( xDH )
}
else
{
xDH = 0
}
xSC = 1 + ( 0.045 * xC1 )
xSH = 1 + ( 0.015 * xC1 )
xDL /= WHT-L
xDC /= WHT-C * xSC
xDH /= WHT-H * xSH
Delta E94 = sqrt( xDL ^ 2 + xDC ^ 2 + xDH ^ 2 )
28、Delta E2000
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CIE-L*1, CIE-a*1, CIE-b*1 //Color #1 CIE-L*ab values
CIE-L*2, CIE-a*2, CIE-b*2 //Color #2 CIE-L*ab values
WHT-L, WHT-C, WHT-H //Wheight factors
xC1 = sqrt( CIE-a*1 * CIE-a*1 + CIE-b*1 * CIE-b*1 )
xC2 = sqrt( CIE-a*2 * CIE-a*2 + CIE-b*2 * CIE-b*2 )
xCX = ( xC1 + xC2 ) / 2
xGX = 0.5 * ( 1 - sqrt( ( xCX ^ 7 ) / ( ( xCX ^ 7 ) + ( 25 ^ 7 ) ) ) )
xNN = ( 1 + xGX ) * CIE-a*1
xC1 = sqrt( xNN * xNN + CIE-b*1 * CIE-b*1 )
xH1 = CieLab2Hue( xNN, CIE-b*1 )
xNN = ( 1 + xGX ) * CIE-a*2
xC2 = sqrt( xNN * xNN + CIE-b*2 * CIE-b*2 )
xH2 = CieLab2Hue( xNN, CIE-b*2 )
xDL = CIE-L*2 - CIE-L*1
xDC = xC2 - xC1
if ( ( xC1 * xC2 ) == 0 ) {
xDH = 0
}
else {
xNN = round( xH2 - xH1, 12 )
if ( abs( xNN ) <= 180 ) {
xDH = xH2 - xH1
}
else {
if ( xNN > 180 ) xDH = xH2 - xH1 - 360
else xDH = xH2 - xH1 + 360
}
}
xDH = 2 * sqrt( xC1 * xC2 ) * sin( dtor( xDH / 2 ) )
xLX = ( CIE-L*1 + CIE-L*2 ) / 2
xCY = ( xC1 + xC2 ) / 2
if ( ( xC1 * xC2 ) == 0 ) {
xHX = xH1 + xH2
}
else {
xNN = abs( round( xH1 - xH2, 12 ) )
if ( xNN > 180 ) {
if ( ( xH2 + xH1 ) < 360 ) xHX = xH1 + xH2 + 360
else xHX = xH1 + xH2 - 360
}
else {
xHX = xH1 + xH2
}
xHX /= 2
}
xTX = 1 - 0.17 * cos( dtor( xHX - 30 ) ) + 0.24
* cos( deg2rad( 2 * xHX ) ) + 0.32
* cos( deg2rad( 3 * xHX + 6 ) ) - 0.20
* cos( dtor( 4 * xHX - 63 ) )
xPH = 30 * exp( - ( ( xHX - 275 ) / 25 ) * ( ( xHX - 275 ) / 25 ) )
xRC = 2 * sqrt( ( xCY ^ 7 ) / ( ( xCY ^ 7 ) + ( 25 ^ 7 ) ) )
xSL = 1 + ( ( 0.015 * ( ( xLX - 50 ) * ( xLX - 50 ) ) )
/ sqrt( 20 + ( ( xLX - 50 ) * ( xLX - 50 ) ) ) )
xSC = 1 + 0.045 * xCY
xSH = 1 + 0.015 * xCY * xTX
xRT = - sin( deg2rad( 2 * xPH ) ) * xRC
xDL = xDL / ( WHT-L * xSL )
xDC = xDC / ( WHT-C * xSC )
xDH = xDH / ( WHT-H * xSH )
Delta E00 = sqrt( xDL ^ 2 + xDC ^ 2 + xDH ^ 2 + xRT * xDC * xDH )
CieLab2Hue( var_a, var_b ) //Function returns CIE-H° value
{
var_bias = 0
if ( var_a >= 0 && var_b == 0 ) return 0
if ( var_a < 0 && var_b == 0 ) return 180
if ( var_a == 0 && var_b > 0 ) return 90
if ( var_a == 0 && var_b < 0 ) return 270
if ( var_a > 0 && var_b > 0 ) var_bias = 0
if ( var_a < 0 ) var_bias = 180
if ( var_a > 0 && var_b < 0 ) var_bias = 360
return ( rad2deg( atan( var_b / var_a ) ) + var_bias )
}
29、Delta CMC
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CIE-L*1, CIE-a*1, CIE-b*1 //Color #1 CIE-L*ab values
CIE-L*2, CIE-a*2, CIE-b*2 //Color #2 CIE-L*ab values
WHT-L, WHT-C //Weight factors
xC1 = sqrt( ( CIE-a*1 ^ 2 ) + ( CIE-b*1 ^ 2 ) )
xC2 = sqrt( ( CIE-a*2 ^ 2 ) + ( CIE-b*2 ^ 2 ) )
xff = sqrt( ( xC1 ^ 4 ) / ( ( xC1 ^ 4 ) + 1900 ) )
xH1 = CieLab2Hue( CIE-a*1, CIE-b*1 )
if ( xH1 < 164 || xH1 > 345 ) xTT = 0.36 + abs( 0.4 * cos( dtor( 35 + xH1 ) ) )
else xTT = 0.56 + abs( 0.2 * cos( dtor( 168 + xH1 ) ) )
if ( CIE-L*1 < 16 ) xSL = 0.511
else xSL = ( 0.040975 * CIE-L*1 ) / ( 1 + ( 0.01765 * CIE-L*1 ) )
xSC = ( ( 0.0638 * xC1 ) / ( 1 + ( 0.0131 * xC1 ) ) ) + 0.638
xSH = ( ( xff * xTT ) + 1 - xff ) * xSC
xDH = sqrt( ( CIE-a*2 - CIE-a*1 ) ^ 2 + ( CIE-b*2 - CIE-b*1 ) ^ 2 - ( xC2 - xC1 ) ^ 2 )
xSL = ( CIE-L*2 - CIE-L*1 ) / ( WHT-L * xSL )
xSC = ( xC2 - xC1 ) / ( WHT-C * xSC )
xSH = xDH / xSH
Delta CMC = sqrt( xSL ^ 2 + xSC ^ 2 + xSH ^ 2 )
CieLab2Hue( var_a, var_b ) //Function returns CIE-H° value
{
var_bias = 0
if ( var_a >= 0 && var_b == 0 ) return 0
if ( var_a < 0 && var_b == 0 ) return 180
if ( var_a == 0 && var_b > 0 ) return 90
if ( var_a == 0 && var_b < 0 ) return 270
if ( var_a > 0 && var_b > 0 ) var_bias = 0
if ( var_a < 0 ) var_bias = 180
if ( var_a > 0 && var_b < 0 ) var_bias = 360
return ( rad2deg( atan( var_b / var_a ) ) + var_bias )
}
30、YUV→ RGB（RGB：0-255）
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Y = 0.299R + 0.587G + 0.114B
U = -0.147R - 0.289G + 0.436B
V = 0.615R - 0.515G - 0.100B
31、YUV→ RGB（RGB：0-255）
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R = Y + 1.14V
G = Y - 0.395U - 0.581V
B = Y + 2.032U