color and image processing faculty of electrical engineering and information technology university...
TRANSCRIPT
![Page 1: Color and Image Processing Faculty of Electrical Engineering and Information Technology University of Aachen D-52056 Aachen, Germany Univ. Prof. Dr.-Ing](https://reader035.vdocuments.net/reader035/viewer/2022070306/5515e592550346cf6f8b4ede/html5/thumbnails/1.jpg)
Color and Image ProcessingFaculty of Electrical Engineering and Information Technology
University of AachenD-52056 Aachen, Germany
Univ. Prof. Dr.-Ing. Bernhard HillTel. +49 (0) 241 802 7703; E-mail: [email protected]
S
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Color and Image Processing:
Main Objectives
Multispectal Image Capture
Multiprimary Display
Softproof Workstation
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Standards developed withinIEC TC 100 - TA2:
“Color Measurement and Management in
Multimedia Systems and Equipment”
Represented in Germany by:DKE (Frankfurt)Committee 742.06
“Multimedia Systeme und Geräte-Farbmessung und Farbmanagment-”
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Projects and standards:
Default RGB colour space - sRGB
Extended precision RGB colour space
Default YCC colour space - sYCC
Equipment using cathode ray tubes
Eqipment using liquid crystal display panels
Eqipment using plasma displays
Colour scanners
Colour printers
Colour cameras
Colour image projectors
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From sRGB to opRGB
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bluered
The story of the default RGB color space
nonlinear distortion
(sRGB: a display color space IEC 61966-2-1)
linear relation between XYZ und sRGB:
Primaries according to chromaticities ITU-R BT.709.3
green
X 0.4124 0.3576 0.1805 RsRGB
Y = 0.2126 0.7152 0.0722 GsRGB
Z 0.0193 0.1192 0.9505 BsRGB
matrix(3x3) RGBsRGBXYZ
RGB´sRGB
digitizationRGB8Bit
Linear transformation
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0.0 1.0
-> RsRGB
0.0
1.0
0
255
R8Bit R´sRGB
RsRGB > 0.0031308
R´sRGB = 1.055 RsRGB(1/2.4) - 0.055
RsRGB > 0.0031308
R´sRGB = 12.92 RsRGB
RsRGB > 0.0031308
R´sRGB = 1.055 RsRGB(1/2.4) - 0.055
RsRGB > 0.0031308
R´sRGB = 12.92 RsRGB
Nonlinear distortion:
R8Bit = round[255 R´sRGB]R8Bit = round[255 R´sRGB]
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550
600
500
chromaticity diagramand sRGB
typical location ofprimaries of LCD-displays
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550
600
500
RGB-Cube and optimal color space
planes of constant lightness spaced Eab = 10 units
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550
600
500
RGB-Cube and optimal color space
planes of constant lightness spaced Eab = 10 units
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bluered
Scene-oriented and extended RGB colour spaceIEC 61966-2-2
linear relation between XYZ und sRGB:
Primaries according to chromaticities ITU-R BT.709.3
green
X 0.4124 0.3576 0.1805 RscRGB
Y = 0.2126 0.7152 0.0722 GscRGB
Z 0.0193 0.1192 0.9505 BscRGB
matrix(3x3) RGBscRGBXYZ
digitization 16 BitsRGBscRGB(16)
linear transformation
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RscRGB
1.0
~7.5
8192
127
16384
RscRGB(16)
65535
4096
0
12288
4096
1.5
~ - 0.5
0.0
RscRGB(16) = round[8192 RscRGB]+4096RscRGB(16) = round[8192 RscRGB]+4096
range brighter than the white point
the range from -0.5 to 1.5 covers thewhole space of visible surface colors
(optimal color space)
the range from -0.5 to 1.5 covers thewhole space of visible surface colors
(optimal color space)
1.0RscRGB -->
0
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Optional RGB Colour SpaceIEC 61966-2-5
matrix(3x3) RGBsRGBXYZ Linear transformation
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550
600
500
chromaticity diagramand sRGB
wide gamut colour space!
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bluered
Optional RGB Colour SpaceIEC 61966-2-5
nonlinear distortion
linear relation between XYZ und sRGB:
Primaries according to CIE 122:1996 chromaticities
green
X 0.5767 0.1856 0.1882 RsRGB
Y = 0.2973 0.6274 0.0753 GsRGB
Z 0.0270 0.0707 0.9913 BsRGB
matrix(3x3) RGBsRGBXYZ
RGB´sRGB
digitizationRGB8Bit
Linear transformation
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0.0 1.0
-> RopRGB
0
255
RopRGB(8)
0.0
1.0
R´opRGB
R´opRGB = RopRGB(1/2.2)R´opRGB = RopRGB
(1/2.2)
Nonlinear distortion:
R8Bit = round[255 R´sRGB]R8Bit = round[255 R´sRGB]RopRGB(N) = round[(2N-1) R´opRGB]RopRGB(N) = round[(2N-1) R´opRGB]
1.0
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Luma-Chroma Color Space sYCCIEC 61966-2-1 Appendix
nonlinear distortion(extended gamut)
transformation from sRGB´ into sYCC´components:
Y´sYCC 0.2990 0.5870 0.1140 R´sRGB
Cb´sYCC = -0.1687 -0.3312 0.5000 G´sRGB
Cr´sYCC 0.5000 -0.4187 -0.0813 B´sRGB
matrix(3x3) RGBsRGBXYZ
RGB´sRGB
digitization 8 BitYCC´sYCC
linear transformation
matrix(3x3) linear transformation
YCCsYCC(8)
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0.0 1.0
-> RsRGB
extended nonlinear distortion:
1.01.0
R´sRGB
0.0
-0.5
1.0
0.5
RsRGB > 0.0031308
R´sRGB = 1.055 RsRGB(1/2.4) - 0.055
-0.0031308 <= RsRGB >= 0.0031308
R´sRGB = 12.92 RsRGB
RsRGB < -0.0031308
R´sRGB = -1.055 RsRGB(1/2.4) + 0.055
RsRGB > 0.0031308
R´sRGB = 1.055 RsRGB(1/2.4) - 0.055
-0.0031308 <= RsRGB >= 0.0031308
R´sRGB = 12.92 RsRGB
RsRGB < -0.0031308
R´sRGB = -1.055 RsRGB(1/2.4) + 0.055
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0
255
YsYCC(8)
YsYCC(8) = round[255 Y´sYCC]YsYCC(8) = round[255 Y´sYCC]
CbsYCC(8) = round[255 Cb´sYCC] + 128CbsYCC(8) = round[255 Cb´sYCC] + 128
CrsYCC(8) = round[255 Cr´sYCC] + 128CrsYCC(8) = round[255 Cr´sYCC] + 128
- digital values below 0 and above 255 are clipped
- the color space covered by sYCC is larger than that of sRGB
but smaller than the optimal color space!
digitization of sYCC´ components:
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Extended gamut YCC colour space xvYCCIEC 61966-2-4
nonlinear distortion(extended gamut)
matrix(3x3) RGBXYZ
RGB´
digitization 8 Bit
YCC´601
linear transformation
matrix(3x3)linear transformation
YCC´709
matrix(3x3)
ITU-R BT.6014:3 and 16:9 TV
ITU-R BT.709HDTV
YCCxyYCC(8) YCCxyYCC(8)
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0.0 1.0
-> R
extended nonlinear distortion:
1.01.0
R´
0.0
-0.5
1.0
0.5
1.086
-0.758
RsRGB > 0.081
R´ = 1.099 R0.45 - 0.099
-0.081 <= R >= 0.081
R´ = 4.5 R
RsRGB < -0.081
R´ = -1.099(-R )0.45 + 0.099
RsRGB > 0.081
R´ = 1.099 R0.45 - 0.099
-0.081 <= R >= 0.081
R´ = 4.5 R
RsRGB < -0.081
R´ = -1.099(-R )0.45 + 0.099
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Transformation from RGB´ to xvYCC´ components
transformation according to R BT.601
Y´601 0.2990 0.5870 0.1140 R´Cb´601 = -0.1687 -0.3312 0.5000 G´ Cr´601 0.5000 -0.4187 -0.0813 B´
Y´709 0.2126 0.7152 0.0722 R´Cb´709 = -0.1146 -0.3854 0.5000 G´ Cr´709 0.5000 -0.4542 -0.0458 B´
transformation according to R BT.709
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0
235
YxyYCC(8)
YxyYCC(8) = round[219 Y´nnn + 16]YxyYCC(8) = round[219 Y´nnn + 16]
CbxvYCC(8) = round[224 Cb´sYCC] + 128CbxvYCC(8) = round[224 Cb´sYCC] + 128
CrxvYCC(8) = round[224 Cr´sYCC] + 128CrxvYCC(8) = round[224 Cr´sYCC] + 128
digitization of YCC´ components:
16 black
255
white point
- the complete optimal color space is covered
- higher quantization in 10 Bits or 16 Bitsis defined as well
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Thank you for listening !
If you like to experience the standards of the default RGB and YCC colour spaces,
look to your TV and DVD multimedia home equipment !
Details of the standards are available from the publications of IEC