1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T T.88TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Amendment 2(06/2003) SERIES T: TERMINALS FOR TELEMATIC SERVICES Information technology Lossy/lossless coding of bi-level images Amendment 2: Extension of adaptive templates for halftone coding ITU-T Reco
2、mmendation T.88 (2000) Amendment 2 ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) i INTERNATIONAL STANDARD ISO/IEC 14492 ITU-T RECOMMENDATION T.88 Information technology Lossy/lossless coding of bi-level images Amendment 2 Extension of adaptive templates for halftone coding Summary The objective of this ame
3、ndment is to further improve JBIG2s compression of periodic bi-level images, like the halftones used in printing. In particular, it improves compression for the clustered-dot halftones often used in very high resolution commercial printing. When applying the appropriate 16-pixel JBIG2 template for s
4、uch applications, this amendment facilitates more compression by increasing the number of moveable (Adaptive Template, AT) pixels from 4 to 12. For periodic halftones at resolutions of over 2400 dpi, effectively exploiting these 12 AT pixels yields approximately 20% better compression than the best
5、obtainable with the current 16-pixel JBIG2 template (by optimizing its maximum of 4 AT pixels). To signal the presence of this amendments datastreams, new flag bits have been defined for both the overall JBIG2 File header and for relevant image Segment headers. The flag bits permit early detection o
6、f this amendments datastreams, making it possible to quickly prevent current JBIG2 decoders from attempting to decode these new datastreams. Source Amendment 2 to ITU-T Recommendation T.88 (2000) was prepared by ITU-T Study Group 16 (2001-2004) and approved on 29 June 2003. An identical text is also
7、 published as ISO/IEC 14492, Amendment 2. ii ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of I
8、TU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics
9、for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepare
10、d on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may c
11、ontain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to expres
12、s requirements. The use of such words does not suggest that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Proper
13、ty Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had received notice of intel
14、lectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2003 All rights reserved. No part of this pu
15、blication may be reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) iii CONTENTS Page 1) Subclause 4.2 1 2) Subclause 6.2.2. 2 3) Subclause 6.2.5.3 2 4) Subclause 6.2.5.4 3 5) Subclause 6.2.5.7 4 6) Subclause 7.4.6.2 4 7) Subclaus
16、e 7.4.6.2 4 8) Subclause 7.4.6.3 5 9) Subclause 7.4.6.4 6 10) Annex D.4.2 . 6 11) Annex F 7 ISO/IEC 14492:2001/Amd.2:2003 (E) ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) 1 INTERNATIONAL STANDARD ITU-T RECOMMENDATION Information technology Lossy/lossless coding of bi-level images Amendment 2 Extension of
17、adaptive templates for halftone coding 1) Subclause 4.2 a) Eight symbols for additional adaptive template pixels (from A5to A12) are added after A4as follows (with the additions underlined): A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12Adaptive template pixels in the generic region decoding proc
18、edure b) A new symbol “EXTTEMPLATE“ is inserted after the symbol “EXRUNLENGTH“ as follows (with the additions underlined): EXRUNLENGTH The length of a run of identical export flag values EXTTEMPLATE A parameter indicating whether extended reference template is used in a generic region decoding proce
19、dure c) New 16 symbols “GBATXi“ and “GBATYi“ (i=5,.,12) are inserted after “GBATY4“ as follows (with the additions underlined): GBATY4The Y location of adaptive template pixel 4 in a generic region decoding procedure GBATX5 The X location of adaptive template pixel 5 in a generic region decoding pro
20、cedure GBATY5 The Y location of adaptive template pixel 5 in a generic region decoding procedure GBATX6 The X location of adaptive template pixel 6 in a generic region decoding procedure GBATY6 The Y location of adaptive template pixel 6 in a generic region decoding procedure GBATX7 The X location o
21、f adaptive template pixel 7 in a generic region decoding procedure GBATY7 The Y location of adaptive template pixel 7 in a generic region decoding procedure GBATX8 The X location of adaptive template pixel 8 in a generic region decoding procedure GBATY8 The Y location of adaptive template pixel 8 in
22、 a generic region decoding procedure GBATX9 The X location of adaptive template pixel 9 in a generic region decoding procedure GBATY9 The Y location of adaptive template pixel 9 in a generic region decoding procedure GBATX10 The X location of adaptive template pixel 10 in a generic region decoding p
23、rocedure GBATY10 The Y location of adaptive template pixel 10 in a generic region decoding procedure GBATX11 The X location of adaptive template pixel 11 in a generic region decoding procedure GBATY11 The Y location of adaptive template pixel 11 in a generic region decoding procedure GBATX12 The X l
24、ocation of adaptive template pixel 12 in a generic region decoding procedure GBATY12 The Y location of adaptive template pixel 12 in a generic region decoding procedure ISO/IEC 14492:2001/Amd.2:2003 (E) 2 ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) 2) Subclause 6.2.2 In Table 2, new symbols “EXTTEMPLATE“
25、, “GBATXi“ and “GBATYi“ (i=5,.,12) are inserted, and the notes of the table are revised as follows (with the additions and revisions underlined): Table 2 Parameters for the generic region decoding procedure Name Type Size (bits) Signed? Description and restrictions (Leave untouched) TPGDON Integer 1
26、 N Whether typical prediction is used. a)EXTTEMPLATE Integer 1 N Whether extended reference template is used. e) (Leave untouched) GBATY4Integer 8 Y The Y location of the adaptive template pixel A4. b)GBATX5 Integer 8 Y The X location of the adaptive template pixel A5. d)GBATY5 Integer 8 Y The Y loc
27、ation of the adaptive template pixel A5. d)GBATX6 Integer 8 Y The X location of the adaptive template pixel A6. d)GBATY6 Integer 8 Y The Y location of the adaptive template pixel A6. d)GBATX7 Integer 8 Y The X location of the adaptive template pixel A7. d)GBATY7 Integer 8 Y The Y location of the ada
28、ptive template pixel A7. d)GBATX8 Integer 8 Y The X location of the adaptive template pixel A8. d)GBATY8 Integer 8 Y The Y location of the adaptive template pixel A8. d)GBATX9 Integer 8 Y The X location of the adaptive template pixel A9. d)GBATY9 Integer 8 Y The Y location of the adaptive template p
29、ixel A9. d)GBATX10 Integer 8 Y The X location of the adaptive template pixel A10. d)GBATY10 Integer 8 Y The Y location of the adaptive template pixel A10. d)GBATX11 Integer 8 Y The X location of the adaptive template pixel A11. d)GBATY11 Integer 8 Y The Y location of the adaptive template pixel A11.
30、 d)GBATX12 Integer 8 Y The X location of the adaptive template pixel A12. d)GBATY12 Integer 8 Y The Y location of the adaptive template pixel A12. d)a)Unused if MMR = 1 b)Unused if MMR = 1 or GBTEMPLATE 0 c)Unused if USESKIP = 0 or MMR = 1 d)Used only if MMR = 0 and GBTEMPLATE = 0 and EXTTEMPLATE =
31、1 e)Used only if MMR = 0 and GBTEMPLATE = 0 3) Subclause 6.2.5.3 a) The identification number of Figure 3 is changed to “Figure 3(a)“, and its caption is revised (with the additions and revisions underlined): X A4 XXXA3 A2 XXX X XA1 XXXFigure 3(a) Template when GBTEMPLATE = 0 and EXTTEMPLATE = 0, sh
32、owing the AT pixels at their nominal locations ISO/IEC 14492:2001/Amd.2:2003 (E) ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) 3 b) New Figure 3(b) is inserted as follows: X A11 A4 A2 A5 A9 A12 A3 X X X A6 A10A8 A7 A1 Figure 3(b) Template when GBTEMPLATE = 0 and EXTTEMPLATE = 1, showing the AT pixels at th
33、eir nominal locations c) The second paragraph in subclause 6.2.5.3 is revised as follows (with the additions and revisions underlined): Figure 3(a) shows the template which shall be used when GBTEMPLATE is 0 and EXTTEMPLATE is 0. Figure 3(b) shows the template which shall be used when GBTEMPLATE is
34、0 and EXTTEMPLATE is 1. Figure 4 shows the template which shall be used when GBTEMPLATE is 1. Figure 5 shows the template which shall be used when GBTEMPLATE is 2. Figure 6 shows the template which shall be used when GBTEMPLATE is 3. In each of these figures, the pixel denoted by a circle correspond
35、s to the pixel to be coded and is not part of the template. The pixels denoted by X correspond to ordinary pixels in the template. The pixels denoted A1-A12are special pixels in the template. They are denoted “adaptive“ or AT pixels. These pixels are special in that their locations are not fixed, bu
36、t can be placed at different locations. See 6.2.5.4 for a description of AT pixels. The legends A1-A12indicate the AT pixels 1 to 12. The pixels actual locations are specified as parameters to this decoding procedure; Figures 3-6 show the nominal locations of these AT pixels for each template. 4) Su
37、bclause 6.2.5.4 a) The second paragraph is revised as follows (with the additions and revisions underlined): The pixels that are allowed to change are called AT pixels. Their nominal locations are indicated by A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, and A12 in Figures 3(a), 3(b), 4, 5 and 6. N
38、ote that some templates have fewer than sixteen AT pixels. In general, an AT pixel can be located anywhere in the field shown in Figure 7, not including the current pixel. Hence, there is the possibility to use an effective template size of 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, or 4 pixels by havin
39、g the moved location of the AT pixel overlap a regular template pixel. The actual locations of the AT pixels for any invocation of this decoding procedure are specified as parameters to the decoding procedure. The location of the pixel A1is given by (GBATX1, GBATY1). If GBTEMPLATE is 0, then: the lo
40、cation of the pixel A2is given by (GBATX2, GBATY2); the location of the pixel A3is given by (GBATX3, GBATY3); and the location of the pixel A4is given by (GBATX4, GBATY4). Additionally, if GBTEMPLATE is 0 and EXTTEMPLATE is 1, then: the location of the pixel A5is given by (GBATX5, GBATY5); the locat
41、ion of the pixel A6is given by (GBATX6, GBATY6); the location of the pixel A7is given by (GBATX7, GBATY7); the location of the pixel A8is given by (GBATX8, GBATY8); the location of the pixel A9is given by (GBATX9, GBATY9); the location of the pixel A10is given by (GBATX10, GBATY10); the location of
42、the pixel A11is given by (GBATX11, GBATY11); the location of the pixel A12is given by (GBATX12, GBATY12). b) Note 2 is revised as follows (with the additions and revisions underlined): NOTE 2 The indices of the AT pixels in Figures 3(a) and 3(b) correspond to the expected goodness. If moving only on
43、e AT pixel from the nominal location shown in Figure 3(a), it is advisable to move A4. The next pixel to move is A 3 and so on. ISO/IEC 14492:2001/Amd.2:2003 (E) 4 ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) c) Table 5 is revised as follows (with the additions and revisions underlined): Table 5 The nomin
44、al values of the AT pixel locations GBTEMPLATE 0 0 1 2 3 EXTTEMPLATE 1 0 0 0 0 GBATX1GBATY12 0 3 1 3 1 2 1 2 1 GBATX2GBATY20 2 3 1 NA NA NA NA NA NA GBATX3GBATY32 1 2 2 NA NA NA NA NA NA GBATX4GBATY41 2 2 2 NA NA NA NA NA NA GBATX5 GBATY5 1 2 NA NA NA NA NA NA NA NA GBATX6 GBATY6 2 1 NA NA NA NA NA
45、NA NA NA GBATX7 GBATY7 3 0 NA NA NA NA NA NA NA NA GBATX8 GBATY8 4 0 NA NA NA NA NA NA NA NA GBATX9 GBATY9 2 2 NA NA NA NA NA NA NA NA GBATX10 GBATY10 3 1 NA NA NA NA NA NA NA NA GBATX11 GBATY11 2 2 NA NA NA NA NA NA NA NA GBATX12 GBATY12 3 1 NA NA NA NA NA NA NA NA NOTE NA means that the parameter
46、has no nominal value. 5) Subclause 6.2.5.7 The step d) ii) is changed as follows (with the additions and revisions underlined): d) If LTP = 0 then, from left to right, decode each pixel of the current row of GBREG. The procedure for each pixel is as follows: i) If USESKIP is 1 and the pixel in the b
47、itmap SKIP at the location corresponding to the current pixel is 1, then set the current pixel to 0. ii) Otherwise: Place the template given by parameters GBTEMPLATE, GBATX1through GBATX12 and GBATY1through GBATY12 so that the current pixel is aligned with the location denoted by a circle in the fig
48、ure describing the appearance of the template with identifier GBTEMPLATE. 6) Subclause 7.4.6.2 a) Figure 46 is replaced by the following figure: EXTTEMPLATE Reserved Must be 0 TPGDON GBTEMPLATE MMR 7 6 5 4 3 2 1 0 Figure 46 Generic region segment flags field structure 7) Subclause 7.4.6.2 The notati
49、ons of Bit 4 are added for EXTTEMPLATE, and reserved bits are changed to Bits 5-7 as follows (with the additions and revisions underlined): Bit 4 EXTTEMPLATE This field specifies whether extended reference template is used. Bits 5-7 Reserved; must be zero. ISO/IEC 14492:2001/Amd.2:2003 (E) ITU-T Rec. T.88 (2000)/Amd.2 (06/2003) 5 8) Subclause 7.4.6.3 a) The first paragraph is changed as follows (with the additions and revisions underlined): This field is on
