Transcript Color and Image Processing

Color and Image Processing
Faculty of Electrical Engineering and Information Technology
University of Aachen
D-52056 Aachen, Germany
Univ. Prof. Dr.-Ing. Bernhard Hill
Tel. +49 (0) 241 802 7703; E-mail: [email protected]
Sl
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Color and Image Processing:
Main Objectives
Multispectal Image Capture
Multiprimary Display
Softproof Workstation
Standards developed within
IEC 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 printers
Colour scanners
Colour cameras
Colour image projectors
From sRGB to opRGB
The story of the default RGB color space
(sRGB: a display color space IEC 61966-2-1)
Linear transformation
XYZ
matrix(3x3)
RGBsRGB
nonlinear distortion
RGB´sRGB
RGB8Bit
digitization
linear relation between XYZ und sRGB:
X
0.4124
Y = 0.2126
Z
0.0193
red
0.3576
0.7152
0.1192
0.1805
0.0722
0.9505
green
blue
RsRGB
GsRGB
BsRGB
Primaries according to chromaticities ITU-R BT.709.3
R8Bi
t
255
Nonlinear distortion:
R´sRGB
1.0
-> RsRGB
0
RsRGB > 0.0031308
0.0
0.0
R´sRGB = 1.055 RsRGB(1/2.4) - 0.055
R8Bit = round[255 R´sRGB]
RsRGB > 0.0031308
R´sRGB = 12.92 RsRGB
1.0
chromaticity diagram
and sRGB
550
500
typical location of
primaries of
LCD-displays
600
RGB-Cube and optimal color space
550
500
600
planes of constant lightness spaced DEab = 10 units
RGB-Cube and optimal color space
550
500
600
planes of constant lightness spaced DEab = 10 units
Scene-oriented and extended RGB colour space
IEC 61966-2-2
XYZ
matrix(3x3)
RGBscRGB
RGBscRGB(16)
linear transformation
digitization 16 Bits
linear relation between XYZ und sRGB:
X
0.4124
Y = 0.2126
Z
0.0193
red
0.3576
0.7152
0.1192
0.1805
0.0722
0.9505
green
blue
RscRGB
GscRGB
BscRGB
Primaries according to chromaticities ITU-R BT.709.3
65535
~7.5
R
=
round[8192
R
]+4096
scRGB(16)
scRGB
R
R
the range from -0.5 to 1.5 covers the
whole space of visible surface colors
(optimal color space)
scRGB(16)
scRGB
1.5
12288
1.0
8192
16384
4096
127
4096
0
range brighter than the white point
0.0
0
1.0
RscRGB -->
~ - 0.5
Optional RGB Colour Space
XYZ
matrix(3x3)
IEC 61966-2-5
RGBsRGB
Linear transformation
chromaticity diagram
and sRGB
550
wide gamut colour
space!
500
600
Optional RGB Colour Space
XYZ
matrix(3x3)
IEC 61966-2-5
RGBsRGB
Linear transformation
nonlinear distortion
RGB´sRGB
RGB8Bit
digitization
linear relation between XYZ und sRGB:
X
0.5767
Y = 0.2973
Z
0.0270
red
0.1856
0.6274
0.0707
0.1882
0.0753
0.9913
green
blue
RsRGB
GsRGB
BsRGB
Primaries according to CIE 122:1996 chromaticities
Nonlinear distortion:
RopRGB(8
R´opRGB
255
1.0
)
1.0
-> RopRGB
0
0.0
0.0
RR8Bit = round[255
R´sRGB
N-1)] R´
=
round[(2
opRGB(N)
opRGB]
R´opRGB = RopRGB(1/2.2)
1.0
Luma-Chroma Color Space sYCC
XYZ
IEC 61966-2-1 Appendix
matrix(3x3)
RGBsRGB
linear transformation
RGB´sRGB
matrix(3x3)
YCC´sYCC
nonlinear distortion
(extended gamut)
linear transformation
digitization 8 Bit
YCCsYCC(8)
transformation from sRGB´ into sYCC´components:
Y´sYCC
0.2990
Cb´sYCC = -0.1687
Cr´sYCC
0.5000
0.5870
-0.3312
-0.4187
0.1140
0.5000
-0.0813
R´sRGB
G´sRGB
B´sRGB
R´sRGB
RsRGB > 0.0031308
1.0
extended nonlinear distortion:
1.0
R´sRGB = 1.055 RsRGB(1/2.4) - 0.055
0.5
-0.0031308 <= RsRGB >= 0.0031308
R´sRGB = 12.92 RsRGB
0.0
RsRGB < -0.0031308
-> RsRGB
0.0
R´sRGB = -1.055 RsRGB(1/2.4) + 0.055
-0.5
1.0
digitization of sYCC´ components:
YsYCC(8)
255
Yvalues
= round[255
]
- digital
below
0 and above 255Y´
aresYCC
clipped
sYCC(8)
- the color space covered by sYCC
is larger than that of sRGB
but smaller
than the optimal
space!
CbsYCC(8)
= round[255
Cb´color
sYCC] + 128
0
CrsYCC(8) = round[255 Cr´sYCC] + 128
Extended gamut YCC colour space xvYCC
IEC 61966-2-4
XYZ
matrix(3x3)
RGB
linear transformation
RGB´
nonlinear distortion
(extended gamut)
matrix(3x3)
matrix(3x3)
YCC´601
YCC´709
ITU-R BT.601
4:3 and 16:9 TV
ITU-R BT.709
HDTV
YCCxyYCC(8)
linear transformation
YCCxyYCC(8) digitization 8 Bit
R´
1.086
1.0
extended nonlinear distortion:
RsRGB > 0.081
R´ = 1.099 R0.45 -
1.0
-0.081 <= R >= 0.081
0.5
0.0
-0.5
-0.758
0.099
R´ = 4.5 R
0.0
RsRGB < -0.081
-> R
1.0
R´ = -1.099(-R )0.45 + 0.099
Transformation from RGB´ to xvYCC´ components
transformation according to R BT.601
Y´601
Cb´601
Cr´601
=
0.2990
-0.1687
0.5000
0.5870
-0.3312
-0.4187
0.1140
0.5000
-0.0813
R´
G´
B´
0.2126 0.7152 0.0722
-0.1146 -0.3854 0.5000
0.5000 -0.4542 -0.0458
R´
G´
B´
transformation according to R BT.709
Y´709
Cb´709
Cr´709
=
YxyYCC(8)
digitization of YCC´ components:
255
235 white point
round[219
Y´is nnn
+ 16]
-Ythe
complete=optimal
color space
covered
xyYCC(8)
16
0
black
-
higher quantization in 10 Bits or 16 Bits
is defined as well
CbxvYCC(8) = round[224 Cb´sYCC] + 128
CrxvYCC(8) = round[224 Cr´sYCC] + 128
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
Thank you for listening !