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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

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

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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-

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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 ) 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

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> 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 ]

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

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

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

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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

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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

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

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chromaticity diagram and sRGB wide gamut colour space!

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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

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> 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

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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)

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> 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)

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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:

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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)

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> 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 )

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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

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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

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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

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