1、INTERNATIONAL STANDARD I EC 61 966-2-1 1999 AMENDMENT 1 2003-01 Amendment 1 Multimedia systems and equipment - Colour measurement and management - Part 2-1 : Colour management - Default RGB colour space - sRGB Amendement 7 Mesure et gestion de la couleur dans les systmes et appareils multimdia - Par
2、tie 2-7: Gestion de la couleur - Espace chromatique RVB par dfaut - sRVB O IEC 2003 Droits de reproduction rservs - Copyright - all rights reserved International Electrotechnical Commission, 3, rue de Varemb, PO Box 131, CH-I211 Geneva 20, Switzerland Telephone: +41 22 919 02 11 Telefax: +41 22 919
3、03 O0 E-mail: inmailiec.ch Web: www.iec.ch PRICECODE H For price, see current catalogue Commission Electrotechnique Internationale International Electrotechnical Commission MeXayHaPOflHaR 3neKTpOTeXHWIeCKaR KOMMCCMR -2- 61966-2-1 Amend. 1 O IEC:2003(E) 1001555AIFDIS FOREWORD 1001625lRVD This amendme
4、nt has been prepared by Technical Area 2: Colour measurement and management, of IEC technical committee 100: Audio, video and multimedia systems and equipment. The text of this amendment is based on the following documents: I FDIS I Report onvoting I Full information on the voting for the approval o
5、f this amendment can be found in the report on voting indicated in the above table. Page 5 CONTENTS Add the titles of Annexes F, G and H as follows: Annex F (normative) Default YCC encoding transformation for a sadard luma-chroma- chroma colour space: sYCC Annex G (informative) Extended gamut encodi
6、ng for sRGB: bg-sRGB and its YCC transformation: bg-sYCC Annex H (informative) CIELAB (L*a*b*) transformation Page 49 Add the following new Annexes F, G and H after Annex E: 61966-2-1 Amend. 1 O IEC:2003(E) -3- Annex F (normative) Default YCC encoding transformation for a standard luma-chroma-chroma
7、 colour space: sYCC The method of digitization in this annex is designed to complement current sRGB-based colour management strategies by explicitly standardizing a default transformation between sRGB and a standard luma-chroma-chroma colour space (sYCC). Application and hardware developers who want
8、 to support various colour compression schemes based on luma-chroma-chroma spaces can utilize this annex. Since this sYCC colour space is a simple extension of the sRGB colour space as defined in this standard, the same reference conditions are shared by both colour spaces. F.l General The encoding
9、transformations between sYCC values and CIE 1931 XYZ values provide unambiguous methods to represent optimum image colorimetry when viewed on a hypothetical reference display that is capable of producing all colours defined by sYCC encoding, in the reference viewing conditions by the reference obser
10、ver. Non-linear floating point sRGB represent the appearance of the image as displayed on the reference display in the reference viewing condition described in Clause 4 of this standard. F.2 Transformation from sYCC values ( Ysycc, Cbsycc, Crsycc) to CIE 1931 XYZ values The non-linear sYC,C, values
11、can be computed using the following relationship: For 24-bit encoding (8-bit/channel), WDC = 255, KDC = O, Range = 255, and Offset = 128, and the relationship is defined as; 24-bit encoding (8-bitkhannel) shall be the default sYCC encoding bit depth. Other bit depths may be unsupported for general u
12、se. Where other N-bitkhanne1 encoding is supported (N S), the relationship is defined as; -4- 61966-2-1 Amend. 1 O IEC:2003(E) For 24-bit encoding ( 1,000 O 0,000 O 1,402 O Y Ys, = round(WDC - KDC)x YS, + KDC CbSycc = round (Range x Cb SYCC(N) = round 2N - i)x JYCc 1 Cbsycc(N) = r0und(2 - 1)x Cb 30-
13、bit encoding (10-bitkhannel) shall be the default bg-sRGB encoding bit depth. Other bit depths may be unsupported in general use. Where other N-bitkhanne1 encoding is supported (N lo), the relationship is defined as; (G.2) 61966-2-1 Amend. 1 O IEC:2003(E) -9- The non-linear sRGB values are then tran
14、sformed to CIE 1931 XYZ values as follows: + 0,0557 13 RGB = 1,055 For 24-bit encoding ( For 30-bit encoding (10-bitkhannel), WDC = 894, KDC = 384, and the relationship is defined as; (G.12) 61966-2-1 Amend. 1 O IEC:2003(E) - 11 - For 30-bit encoding, the bg-sRGB(,o) values shall be limited to a ran
15、ge from O to 1023 after equation G.12. 30-bit encoding (10-bitkhannel) shall be the default bg-sRGB encoding bit depth. Other bit depths may be unsupported in general use. Where other N-bitchannel encoding is supported (N lo), the relationship is defined as; (G. 1 2) For N-bitchannel encoding (N lo)
16、 the bg-SRGB(N) values shall be limited to a range from O to 2N - 1 after equation G.12. G.4 Transformation between SRG6 8-bit Values ( R,RGB(), GsG(8), Bs(8) and bg-sRGB Ombit values(Rbg-sRGB(lO) Gbg-sRGB(lO)l Bbg-sRGB(lO) The transformation between sRGB 8-bit values and bg-sRGB 10-bit values can
17、be computed using following relationship After equation G.14, the sRGB(,) values shall be limited to a range from O to 255. For the case of N bit encoding; (G.13) (G. 14) (G. 1 3) (G.14) After equation G.14, the sRGB(,) values is limited to a range from 0 to 2N-1 - 12- 61966-2-1 Amend. 1 O IEC:2003(
18、E) The non-linear floating point sYC,C, values can be computed using following relationship For 30-bit encoding (1 O-bitkhannel), WDC = 1023, KDC = O, Range = 1023/2, Offset = 51 2, and the relationship is defined as; (G.16) 30-bit encoding (1 O-bitkhannel) shall be the default bg-sYCC encoding bit
19、depth. Other bit depths may be unsupported in general use. Where other N-bitkhanne1 encoding is supported (N lo), the relationship is defined as; ybg -SYcC(N) YSYCC =(“ 2 -1 (G. 1 6) For 30-bit encoding (1 O-bitkhannel), the non-linear sYC,C, values are then transformed to the non-linear sRGB values
20、 as follows, 1,000 O 0,000 O 1,402 O 1,000 O -0,344 1 -0,714 1 1,000 O 1,772 O 0,000 O (G.17) For N-bitlchannel encoding (N lo), it is recommended to replace the matrix coefficients in the equation G.17 with the coefficients of the inverse matrix of the equation G.18 with enough accuracy decimal poi
21、nts. For example, following matrix with 6 decimal points has enough accuracy for the case of 16-bWchannel. 61966-2-1 Amend. 1 O IEC:2003(E) - 13- 1,000 O00 0,000 037 1,401 988 YJycc 1,000 O00 -0,344 113 -0,714 104 CbCycc 1,000 O00 1,771 978 0,000 135 Criycc (G .I 7) The non-linear sRGB values are th
22、en transformed to CIE 1931 XYZ values using G.3, G.4, G.5, and G.6 G.6 Transformation from CIE 1931 XYZ values to bg-sYCC values ( ybg-sYCCj Cbbg-sYCCj c%g-sYCC) Transformation from CIE 1931 XYZ values to the non-linear sRGB values are defined in G.7 (or G.7), G.8, G.9, and G.lO. The relationship be
23、tween non-linear sRGB and SYCbcr is defined as follows: 0,299 O 0,587 O 0,114 O -0,168 7 -0,331 3 0,500 O 0,500 O - 0,418 7 - 0,081 3 (G.18) NOTE The coefficients in equation F.18 are from ITU-R BT.601-5. The ITU-R BT.601-5 defines Y of YCC to the three decimal place accuracy. An additional decimal
24、place is defined above to be consistent with the other matrix coefficients defined in this standard. Quantization for bg-sYCC is defined as; Ybg-syCC = round(WDC - KDC) YYCC + KDC cbbg -SYCC = round (Range x cCYCC ) + fiet Cbg -sycc = round (Range x Cr. Cbbg-sYCC(lo) = round ( 1023 x Tiycc + 512) (G
25、 20) c%g-sYcC(lo) = round (1023pc + 512) For 30-bit encoding, the bg-sYCC(lo) values shall be limited to a range from O to 1023 after equation G.20. 30-bit encoding (1 O-bitkhannel) shall be the default bg-sYCC encoding bit depth. Other bit depths may be unsupported in general use. Where other N-bi
26、tkhanne1 encoding is supported (N lo), the relationship is defined as; - 14- 61966-2-1 Amend. 1 O IEC:2003(E) (G .20) For N-bitkhanne1 encoding (N 10 ), the bg-sYCC(,) values shall be limited to a range from O to 2N-1 after equation G.20. The maximum luminance of the achromatic axis of bg-sYCC is eq
27、ual to 1,O. The minimum luminance of the achromatic axis of bg-sYCC is equal to 0,O. NOTE The denominator “2“ for Cb and Cr is for covering all optimal colour range. See pp.179 - 181 of I61 The transformation from bg-sRGB 10-bit values to bg-sYCC 10-bit values can be computed using the equations, G.
28、2, G.18 and G.20. For the case of N bit encoding, equations, G.2, G.18 and G.20 should be used. The transformation from bg-sYCC 1 O-bit values and bg-sRGB 1 O-bit values can be computed using the equations, G.16, G.17 and G.12. For the case of N bit encoding, equations, G.16, G.17 and G.12 should be
29、 used. 61966-2-1 Amend. 1 O IEC:2003(E) - 15- Annex H (informative) CI ELAB (L*a*b*) transformation H.l General The following equations describe the relation between sRGB and L*a*b* coordinates according to CIE 15.2:1986. It should be noted that the degree of non-linearity is different from the non-
30、 linear relation between components RsRGB and RsRGB, BsRGB and BsRGB and GsRGB and GRGB. H.2 Use equation (7) in 5.2 to determine XYZ coordinates from RsRBg,GsRGB, BsRB and calculate L*a*b* coordinates according to: Transformation from sRGB into CIELAB (L*a*b*) coordinates L* = 116 f(Y/Yn) - 16 if Y
31、/Yn 0,008856 L* = 903.3 * (Y/Yn) if Y/Yn 0,008856 if Y/Y, 50,008856 if X/Xn 0,008856 if X/Xn 50,008856 if z/z, 0,008856 if Z/Z, 50,008856 and X, Y, Z, are the reference display white point coordinates of illuminant D65 (4.1) with X, = 0,9505 Y, = 1,0000 Z, = 1,0890 - 16- 61966-2-1 Amend. 1 O IEC:200
32、3(E) H.3 Transformation from CIELAB (L*a*b*) coordinates to RsRGBg, GsRB, BsRGB Determine: f (Y/Yn) = (L* + 16) / 116 f (X/X,) = a * / 500 + f ( Y/Y,) (H.2) f(Z/Z,) = f(Y/Y,) - b*/ 200 Calculate XYZ from: X= Xn fW/Xn) i3 X= X, f(X/X,) - 16/116 / 7,787 if f(X/X,) 0,206893 or L* 7,99959 if f(X/X,) 50,
33、206893 or L* 57,99959 Y= Y, f(Y/Yn) I3 if f(Y/Y,) 0,206893 (H.3) Y = Y, f(Y/Y,) - 16/116 / 7,787 if f(Y/Y,) 50,206893 z = Zn f(Z/Zn) i3 if f(z/z,) 0,206893 Z = Z, f(Z/Z,) - 16/116 / 7,787 if f(Z/Z,) 50,206893 XYZ coordinates are converted to RsRBS GsRGB, BsRGB using equation (9) in 5.3. Page 51 Bibl
34、iography Add the following references to the existing list: I61 Wysecki G. and Stiles W.S. Color Science: Concepts and Methods, Quantitative Data and Formulae, 2“d Ed., John Wiley & Sons, Inc. (1982).“ I71 ITU-R BT.601-5, Studio encoding parameters of digital televisions for standard 4:3 and wide-screen 16:9 aspect ratios
