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Color and Image Processing Faculty of Electrical Engineering and Information Technology University of Aachen D-52056 Aachen, Germany Univ. Prof. Dr.-Ing.

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Presentation on theme: "Color and Image Processing Faculty of Electrical Engineering and Information Technology University of Aachen D-52056 Aachen, Germany Univ. Prof. Dr.-Ing."— Presentation transcript:

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) ; S

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

3 Standards developed within IEC TC 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 scanners Colour printers Colour cameras Colour image projectors

5 From sRGB to opRGB

6 bluered The story of the default RGB color space nonlinear distortion (sRGB: a display color space IEC ) linear relation between XYZ und sRGB: Primaries according to chromaticities ITU-R BT green X R sRGB Y = G sRGB Z B sRGB matrix(3x3)RGB sRGB XYZ RGB´ sRGB digitization RGB 8Bit Linear transformation

7 > R sRGB R 8Bi t R´ sRGB R sRGB > R´ sRGB = R sRGB (1/2.4) R sRGB > R´ sRGB = R sRGB R sRGB > R´ sRGB = R sRGB (1/2.4) R sRGB > R´ sRGB = R sRGB Nonlinear distortion: R 8Bit = round[255 R´ sRGB ]

8 chromaticity diagram and sRGB typical location of primaries of LCD-displays

9 RGB-Cube and optimal color space planes of constant lightness spaced E ab = 10 units

10 RGB-Cube and optimal color space planes of constant lightness spaced E ab = 10 units

11 bluered Scene-oriented and extended RGB colour space IEC linear relation between XYZ und sRGB: Primaries according to chromaticities ITU-R BT green X R scRGB Y = G scRGB Z B scRGB matrix(3x3)RGB scRGB XYZ digitization 16 Bits RGB scRGB(16) linear transformation

12 R scRGB 1.0 ~ R scRGB( 16) ~ R scRGB(16) = round[8192 R scRGB ]+4096 range brighter than the white point the range from -0.5 to 1.5 covers the whole space of visible surface colors (optimal color space) the range from -0.5 to 1.5 covers the whole space of visible surface colors (optimal color space) 1.0 R scRGB --> 0

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

14 chromaticity diagram and sRGB wide gamut colour space!

15 bluered Optional RGB Colour Space IEC nonlinear distortion linear relation between XYZ und sRGB: Primaries according to CIE 122:1996 chromaticities green X R sRGB Y = G sRGB Z B sRGB matrix(3x3)RGB sRGB XYZ RGB´ sRGB digitization RGB 8Bit Linear transformation

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

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

18 > R sRGB extended nonlinear distortion: 1.0 R´ sRGB R sRGB > R´ sRGB = R sRGB (1/2.4) = R´ sRGB = R sRGB R sRGB < R´ sRGB = R sRGB (1/2.4) R sRGB > R´ sRGB = R sRGB (1/2.4) = R´ sRGB = R sRGB R sRGB < R´ sRGB = R sRGB (1/2.4)

19 0 255 Y sYCC(8) Y sYCC(8) = round[255 Y´ sYCC ] Cb sYCC(8) = round[255 Cb´ sYCC ] Cr sYCC(8) = round[255 Cr´ sYCC ] 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:

20 Extended gamut YCC colour space xvYCC IEC 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.601 4:3 and 16:9 TV ITU-R BT.709 HDTV YCC xyYCC(8)

21 > R extended nonlinear distortion: 1.0 R´ R sRGB > R´ = R = R´ = 4.5 R R sRGB < R´ = (-R ) R sRGB > R´ = R = R´ = 4.5 R R sRGB < R´ = (-R )

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

23 0 235 Y xyYCC(8) Y xyYCC(8) = round[219 Y´ nnn + 16] Cb xvYCC(8) = round[224 Cb´ sYCC ] Cr xvYCC(8) = round[224 Cr´ sYCC ] digitization of YCC´ components: 16black 255 white point - the complete optimal color space is covered - higher quantization in 10 Bits or 16 Bits is defined as well

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


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