Color and Image Processing lty of Electrical Engineering and Information Techn University of Aachen D-52056 Aachen, Germany Univ. Prof. Dr.-Ing. Bernhard Hill Tel. +49 (0) 241 802 7703; E-mail: [email protected] S
Mar 28, 2015
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
Color and Image Processing:
Main Objectives
Multispectal Image Capture
Multiprimary Display
Softproof Workstation
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-”
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
From sRGB to opRGB
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
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]
550
600
500
chromaticity diagramand sRGB
typical location ofprimaries of LCD-displays
550
600
500
RGB-Cube and optimal color space
planes of constant lightness spaced Eab = 10 units
550
600
500
RGB-Cube and optimal color space
planes of constant lightness spaced Eab = 10 units
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
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
Optional RGB Colour SpaceIEC 61966-2-5
matrix(3x3) RGBsRGBXYZ Linear transformation
550
600
500
chromaticity diagramand sRGB
wide gamut colour space!
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
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
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)
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
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:
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)
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
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
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
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