1、BRITISH STANDARD BS ISO/IEC 7942-4:1998 Information technology Computer graphics and image processing Graphical Kernel Systems (GKS) Part 4: Picture part archive ICS 35.140BSISO/IEC 7942-4:1998 This British Standard, having been prepared under the directionof the DISC Board, waspublished under the a
2、uthorityof the Standards Committee and comes into effect on 15November1998 BSI 05-1999 ISBN 0 580 30723 9 National foreword This British Standard reproduces verbatim ISO7942-4:1998 and implements it as the UK national standard. The UK participation in its preparation was entrusted by Technical Commi
3、ttee IST/31, Computer graphics and image processing, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related in
4、ternational and European developments and promulgate them in the UK. A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be
5、 found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Stan
6、dards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the ISO/IEC title page, pagesii toiv, pages1 to4, an insid
7、e back cover and aback cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date CommentsBSISO/IEC7942-4:1998 BSI 05-1999 i Contents P
8、age National foreword Inside front cover Foreword iii Text of ISO/IEC7942-4 1ii blankBSISO/IEC 7942-4:1998 ii BSI 05-1999 ContentsPage Foreword iii Introduction 1 1 Scope 1 2 Normative references 1 3 Definitions 1 4 Concepts 1 4.1 The structure of a GKS-94 picture part archive 1 4.2 Metafile element
9、s 2 4.3 Delimiter elements 2 4.4 Functional capability 2 4.4.1 Introduction 2 4.4.2 PPA-SET 2 4.5 Representation of picture parts in the picture part archive 3 5 Abstract specification of new element 3 5.1 Data type definitions and abbreviations 3 5.2 Delimiter element 3 6 Encodings of the GKS-94 Pi
10、cture Part Archive 3 6.1 Introduction 3 6.2 Character encoding 3 6.3 Binary encoding 4 6.4 Clear text encoding 4 Annex A (normative) Formal grammar Inside back cover Annex B (normative) New element list Inside back cover B.1 Introduction 5 B.2 Delimiter elements 5 Figure 1 General form of a picture
11、part archive 1 Figure 2 General form of picture parts 1 Table 1 Opcodes for metafile elements 3 Descriptors: Data processing, graphic data processing, image processing, computer software, artificial languages, advanced language, GKS, archives.BSISO/IEC 7942-4:1998 BSI 05-1999 iii Foreword ISO (the I
12、nternational Organization for Standardization) and IEC (theInternational Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISO or IEC participate in the development of International Standards through technical committees estab
13、lished by the respective organization to deal with particular fields of technical activity. ISO and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with ISO and IEC, also take part in the work. In the
14、 field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC1. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least75 % of
15、 the national bodies casting a vote. International Standard ISO/IEC7942-4 was prepared by Joint Technical Committee ISO/IEC JTC1, Information technology, Subcommittee SC24, Computer graphics and image processing. ISO/IEC7942 consists of the following parts, under the general title Information techno
16、logy Computer graphics and image processing Graphical Kernel System (GKS): Part 1: Functional description; Part 2: NDC metafile; Part 3: Audit trail; Part 4: Picture part archive. Annex A and Annex B form an integral part of this part of ISO/IEC7942.iv blankBSISO/IEC 7942-4:1998 BSI 05-1999 1 Introd
17、uction The GKS-94 picture part archive provides a file format and encodings suitable for the storage and retrieval of GKS-94 picture parts. The file format consists of a set of elements that can be used to describe the contents of picture parts. This part of ISO/IEC7942 extends the provisions of ISO
18、/IEC8632:1992/Amd.2:1995. 1 Scope This part of ISO/IEC7942 provides a file format and encodings for the storage and retrieval of GKS-94 picture parts. It is based on Part2 of ISO/IEC7942, the NDC metafile, which is itself an extension of the Computer Graphics Metafile, Version4 defined by ISO/IEC863
19、2:1992/Amd.2:1995 (all parts). 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO/IEC7942. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties
20、 to agreements based on this part of ISO/IEC7942 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO/IEC7942-1:1994, Information technology Compu
21、ter graphics and image processing Graphical Kernel System (GKS) Part1: Functional description. ISO/IEC7942-2:1997, Information technology Computer graphics and image processing Graphical Kernel System (GKS) Part2: NDC metafile. ISO/IEC8632:1992/Amd.2:1995, Information technology Computer graphics Me
22、tafile for the storage and transfer of picture description information (all parts). AMENDMENT2: Application Structuring extensions. 3 Definitions For the purposes of this part of ISO/IEC7942, the definitions given in ISO/IEC7942-1 and ISO/IEC8632-1/Amd.2 apply. 4 Concepts 4.1 The structure of a GKS-
23、94 picture part archive The structure of a GKS-94 picture part archive follows the GKS-94 NDC metafile described in Part2 of this International Standard. This in turn follows the structure of the Computer Graphics Metafile (CGM) standard (ISO/IEC8632-1:1992). The structure of a picture part archive
24、is shown in Figure 1. PPA is used as an abbreviation for PICTURE PART ARCHIVE and MF for metafile. A Computer Graphics Metafile is a collection of elements from the standardized set. The BEGIN PICTURE PART ARCHIVE METAFILE element is followed by the METAFILE DESCRIPTOR (MD). After this the picture p
25、arts follow, each logically independent of each other. Finally the Metafile is ended with an ENDPICTURE PART ARCHIVE element. Apart from the BEGIN PICTURE PART ARCHIVE METAFILE, END METAFILE and Metafile Descriptor elements, the metafile is partitioned into picture parts. All picture parts are mutua
26、lly independent. A picture part consists of a BEGIN PICTURE element, a PICTURE DESCRIPTOR (PD) element, a BEGIN PICTURE BODY element, an arbitrary number of control, graphical and attribute elements and finally an END PICTURE element (see Figure 2). PIC is used as an abbreviation for PICTURE and BEG
27、IN BODY for BEGIN PICTURE BODY. BEGIN PPA MF MD . END MF Figure 1 General form of a picture part archive BEGIN PIC PD BEGIN BODY . END PIC Figure 2 General form of picture partsBSISO/IEC 7942-4:1998 2 BSI 05-1999 4.2 Metafile elements Picture part archives use the same metafile elements as the GKS-9
28、4 NDC metafile except that the delimiter element BEGIN PICTURE PART ARCHIVE METAFILE is used in place of BEGIN NDC METAFILE. The new CGM element is marked by a dagger () in the tables in this section. 4.3 Delimiter elements The picture part archive metafile includes the following new delimiter eleme
29、nt: BEGIN PICTURE PART ARCHIVE METAFILE 4.4 Functional capability 4.4.1 Introduction Following the provisions of ISO/IEC8632-1:1992/Amd.2:1995, the contents of the Computer Graphics Metafile are defined by the METAFILE ELEMENT LIST element. The picture part archive set is designated PPA-SET. 4.4.2 P
30、PA-SET The PPA-SET includes the elements which can appear in the picture part archive. The elements which are not marked by daggers belong to the NDC-SET defined in Part2 of this International Standard. The elements included in the picture part archive are: BSISO/IEC 7942-4:1998 BSI 05-1999 3 4.5 Re
31、presentation of picture parts in the picture part archive As described in 6.4.4 of Part1 of this International Standard, GKS-94 picture part consists of a strict sequence of output primitives. Primitives in a picture part have attributes bound to them in the same way as primitives in the NDC picture
32、. A picture part can be archived by invoking the function ARCHIVE PICTURE PART. Each archive consists of a set of picture parts, with names local to the archive. The name to be given to a picture part in the archive is specified as a parameter to the function ARCHIVE PICTURE PART. A picture part can
33、 be retrieved from the archive by invoking the function RETRIEVE PICTURE PART FROM ARCHIVE. On retrieval a picture part name is supplied. Picture parts are represented in the picture part archive in the same way as NDC pictures in the GKS-94 NDC metafile. Each picture part is delimited by BEGIN PICT
34、URE and END PICTURE metafile elements. The archival name of the picture part is stored in the picture identifier parameter of the BEGIN PICTURE element. 5 Abstract specification of new element 5.1 Data type definitions and abbreviations Data type definitions are the same as those used in CGM Version
35、4. 5.2 Delimiter element BEGIN PICTURE PART ARCHIVE METAFILE identifier This is the first element of a picture part archive. It demarcates the beginning of the Metafile Descriptor. BEGIN PICTURE PART ARCHIVE METAFILE shall occur exactly once in a metafile. The identifier parameter is available for u
36、se by metafile generators and interpreters in a manner that is not further standardized. 6 Encodings of the GKS-94 Picture Part Archive 6.1 Introduction Three encodings are defined for the picture part archive: character, binary and clear text. The picture part archive uses the same metafile element
37、s as the GKS-94 NDC picture metafile with one exception. The element BEGIN PICTURE PART ARCHIVE METAFILE replaces the BEGIN NDC METAFILE element. The representations of this new element are given below. These follow the notational conventions and methods of encoding opcodes described in Part2 of thi
38、s International Standard; these conventions and methods are not repeated here. 6.2 Character encoding The opcode assignment for BEGIN PICTURE PART ARCHIVE METAFILE is given in the table below. Table 1 Opcodes for metafile elements The representation of the element is given below.Opcode 7-Bit coding
39、8-Bit coding BEGIN PICTURE PART ARCHIVE METAFILE opcode 3/0 3/8 03/0 03/8BSISO/IEC 7942-4:1998 4 BSI 05-1999 BEGIN PICTURE PART ARCHIVE METAFILEThe first parameter, substitution-code, is identical to that of the corresponding parameter of the BEGIN METAFILE element in ISO/IEC8632-2:1992/Amd.2:1995.
40、6.3 Binary encoding The representation of the BEGIN PICTURE PART ARCHIVE METAFILE is given below. Code Description 6.4 Clear text encoding The representation of the BEGIN PICTURE PART ARCHIVE METAFILE is given below. The derived name of the BEGIN PICTURE PART ARCHIVE METAFILE element is BEGPPAMF. El
41、ement Element Parameter Parameter Parameter Class0 Id Type List Range Length BEGIN PPA METAFILE 25 SF BS SR 1 BEGIN PPA METAFILE: has1 parameter: P1: (string fixed) metafile name BEGIN PPA METAFILE 4 BEGPPAMFBSISO/IEC 7942-4:1998 BSI 05-1999 Annex A (normative) Formal grammar The formal grammar for
42、the picture part archive is identifical to the formal grammar for the GKS-94 NDC metafile (Annex A of Part2 of this International Standard) except that the first production for the metafile structure (A.3.1): Annex B (normative) New element list B.1 Introduction The following new CGM element is defi
43、ned in this part of ISO/IEC7942. B.2 Delimiter elements BEGIN PICTURE PART ARCHIVE METAFILE.74*is replaced by the production:4*BS ISO/IEC 7942-4:1998 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandard
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