1. Color and Image Processing
Faculty of Electrical Engineering and Information Technology
University of Aachen
D Aachen, Germany
Univ. Prof. Dr.-Ing. Bernhard Hill
Tel. +49 (0) ; Sl jl

2. Color and Image Processing:
Main Objectives
Multispectal Image Capture
Multiprimary Display
Softproof Workstation

3. Standards developed within IEC TC 100 - TA2:
“Color Measurement and Management in
Multimedia Systems and Equipment”
Represented in Germany by:
DKE (Frankfurt)
Committee
“Multimedia Systeme und Geräte
-Farbmessung und Farbmanagment-”

4. 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

5. From sRGB to opRGB

6. (sRGB: a display color space IEC 61966-2-1)
The story of the default RGB color space
(sRGB: a display color space IEC )
Linear transformation
XYZ
matrix(3x3)
RGBsRGB
nonlinear distortion
RGB´sRGB
digitization
RGB8Bit
linear relation between XYZ und sRGB:
X RsRGB
Y = GsRGB
Z BsRGB
red
green
blue
Primaries according to chromaticities ITU-R BT.709.3

7. R´sRGB = 1.055 RsRGB(1/2.4) - 0.055 R8Bit = round[255 R´sRGB]
255
R8Bit
Nonlinear distortion:
R´sRGB
1.0
-> RsRGB
0.0
RsRGB >
R´sRGB = RsRGB(1/2.4)
R´sRGB = RsRGB
0.0
1.0
R8Bit = round[255 R´sRGB]

8. chromaticity diagram and sRGB typical location of primaries of
550
500
typical location of
primaries of
LCD-displays
600

9. RGB-Cube and optimal color space
550
500
600
planes of constant lightness spaced DEab = 10 units

10. RGB-Cube and optimal color space
550
500
600
planes of constant lightness spaced DEab = 10 units

11. Scene-oriented and extended RGB colour space
IEC
XYZ
matrix(3x3)
RGBscRGB
linear transformation
digitization 16 Bits
RGBscRGB(16)
linear relation between XYZ und sRGB:
X RscRGB
Y = GscRGB
Z BscRGB
red
green
blue
Primaries according to chromaticities ITU-R BT.709.3

12. RscRGB(16) = round[8192 RscRGB]+4096
127
16384
RscRGB(16)
65535
4096
12288
~7.5
RscRGB(16) = round[8192 RscRGB]+4096
range brighter than the white point
RscRGB
the range from -0.5 to 1.5 covers the
whole space of visible surface colors
(optimal color space)
1.5
1.0
0.0
1.0
RscRGB -->
~ - 0.5

13. Optional RGB Colour Space
IEC
Linear transformation
XYZ
matrix(3x3)
RGBsRGB

14. wide gamut colour space!
chromaticity diagram
and sRGB
550
wide gamut colour space!
500
600

15. Optional RGB Colour Space
IEC
Linear transformation
XYZ
matrix(3x3)
RGBsRGB
nonlinear distortion
RGB´sRGB
digitization
RGB8Bit
linear relation between XYZ und sRGB:
X RsRGB
Y = GsRGB
Z BsRGB
red
green
blue
Primaries according to CIE 122:1996 chromaticities

16. RopRGB(N) = round[(2N-1) R´opRGB]
255
RopRGB(8)
0.0
1.0
R´opRGB
Nonlinear distortion:
1.0
-> RopRGB
0.0
1.0
R8Bit = round[255 R´sRGB]
RopRGB(N) = round[(2N-1) R´opRGB]
R´opRGB = RopRGB(1/2.2)

17. Luma-Chroma Color Space sYCC
IEC Appendix
XYZ
matrix(3x3)
RGBsRGB
linear transformation
nonlinear distortion
(extended gamut)
RGB´sRGB
matrix(3x3)
linear transformation
YCC´sYCC
digitization 8 Bit
YCCsYCC(8)
transformation from sRGB´ into sYCC´components:
Y´sYCC R´sRGB
Cb´sYCC = G´sRGB
Cr´sYCC B´sRGB

18. R´sRGB = 1.055 RsRGB(1/2.4) - 0.055 R´sRGB = 12.92 RsRGB
-0.5
0.5
extended nonlinear distortion:
RsRGB >
R´sRGB = RsRGB(1/2.4)
<= RsRGB >=
R´sRGB = RsRGB
RsRGB <
R´sRGB = RsRGB(1/2.4)
1.0
-> RsRGB
0.0
1.0

19. digitization of sYCC´ components:
255
YsYCC(8)
digitization of sYCC´ components:
- digital values below 0 and above 255 are clipped
YsYCC(8) = round[255 Y´sYCC]
the color space covered by sYCC
is larger than that of sRGB
but smaller than the optimal color space!
CbsYCC(8) = round[255 Cb´sYCC] + 128
CrsYCC(8) = round[255 Cr´sYCC] + 128

20. Extended gamut YCC colour space xvYCC
IEC
XYZ
matrix(3x3)
RGB
linear transformation
nonlinear distortion
(extended gamut)
RGB´
linear transformation
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)
YCCxyYCC(8)
digitization 8 Bit

21. 1.0 R´
0.0
-0.5
0.5
1.086
-0.758
extended nonlinear distortion:
RsRGB > 0.081
R´ = R
<= R >= 0.081
R´ = 4.5 R
RsRGB <
R´ = (-R )
1.0
-> R
0.0
1.0

22. Transformation from RGB´ to xvYCC´ components
transformation according to R BT.601
Y´ R´
Cb´ = G´
Cr´ B´
transformation according to R BT.709
Y´ R´
Cb´ = G´
Cr´ B´

23. digitization of YCC´ components:
YxyYCC(8)
255
- the complete optimal color space is covered
235
white point
YxyYCC(8) = round[219 Y´nnn + 16] 16
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

24. 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
Thank you for listening !