BS ISO IEC 9637-1-1994 Information technology - Computer graphics - Interfacing techniques for dialogues with graphical devices (CGI) - Data stream binding - Character enc.pdf

1、BRITISH STANDARD BS ISO/IEC 9637-1:1994 Implementation of ISO/IEC 9637-1:1994 Information technology Computer graphics Interfacing techniques for dialogues with graphical devices (CGI) Data stream binding Part 1: Character encodingBSISO/IEC 9637-1:1994 This British Standard, having been prepared und

2、er the directionof the Information Systems Technology StandardsPolicy Committee, waspublishedunder the authorityofthe Standards Boardand comes into effect on 15July1994 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference IST/31 Draft for comment 92/63487

3、 DC ISBN 0 580 23208 5 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Information Systems Technology Standards Policy Committee (IST/-) to Technical Committee IST/31, upon which the following bodies were represented: Department of Trade

4、 and Industry IT Standards Unit (ITD6A) Information Systems Committee of the Universities Funding Council Rutherford Appleton Laboratory Amendments issued since publication Amd. No. Date CommentsBSISO/IEC 9637-1:1994 BSI 02-2000 i Contents Page Committees responsible Inside front cover National fore

5、word ii Foreword iv Text of ISO/IEC 9637-1 1BSISO/IEC 9637-1:1994 ii BSI 02-2000 National foreword This British Standard reproduces verbatim ISO/IEC9637-1:1994 and implements it as the UK national standard. This British Standard is published under the direction of the Information Systems Technology

6、Standards Policy Committee whose Technical Committee IST/31 has the responsibility to: aid enquirers to understand the text; present to the responsible international committee any enquiries on interpretation, or proposals for change, and keep UK interests informed; monitor related international and

7、European developments and promulgate them in the UK. NOTEInternational and European Standards, as well as overseas standards, are available from Customer Services, Publications, BSI, Linford Wood, Milton Keynes, MK146LE. A British Standard does not purport to include all the necessary provisions of

8、a contract. Users of British Standards 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, pagesi andii, theISO/IEC title page, page

9、sii toiv, pages1 to51 and a back 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.ISO/IEC 9637-1:1994 (E) ii BSI 02-2000 Contents Page Foreword iv Introduction 1 0.1 Purpose of

10、 the character encoding 1 0.2 Objectives 1 0.3 Relationship to other International Standards 1 1 Scope 1 2 Normative references 1 3 Notational conventions 2 3.1 7-Bit and 8-Bit code tables 2 3.2 Code extension techniques vocabulary 3 3.2.1 C0 sets 3 3.2.2 C1 sets 3 3.2.3 G sets 3 4 Overall structure

11、 5 4.1 General form of the data stream 5 4.2 Entering and leaving the CGI environment 5 4.2.1 Implicitly entering the CGI environment 5 4.2.2 Designating and invoking the CGI coding environment from ISO 2022 5 4.3 Encoding functions 5 5 Method of encoding opcodes 6 5.1 Encoding technique of the basi

12、c opcode set 6 5.2 Extension mechanism 6 5.3 Opcode assignments 7 5.4 Opcodes for soliciting functions 7 6 Method of encoding parameters 17 6.1 Basic format 17 6.2 Bitstream format 18 6.3 Coding integers (I, IF8, IF16, IF32) 19 6.4 Coding real numbers (R) 19 6.5 Coding Virtual Device Coordinates and

13、 Points (VDC, P) 21 6.6 Coding point list parameters (nP) 21 6.6.1 Displacement mode 21 6.6.2 Incremental mode 21 6.6.3 Incremental mode encoding 25 6.7 Colour specifiers (CI, CD) 26 6.8 Colour lists (nCI, nCD) 26 6.8.1 Normal format (coding type=0) 27 6.8.2 Bitstream format (coding type=1) 27 6.8.3

14、 Runlength format (coding type=2) 27 6.8.4 Runlength bitstream format (coding type=3) 28 6.8.5 Examples 28 6.9 String parameters (S, SF) 29 6.9.1 Overall string parameter format 29 6.9.2 Bit combinations permitted within string parameters of text functions 29 6.9.3 C0 control within string parameter

15、s 30 6.9.4 Using G-sets in string parameters 30 6.9.4.1 String parameters and character sets 30 6.9.4.2 String parameters of other CGI functions 30ISO/IEC 9637-1:1994 (E) BSI 02-2000 iii Page 6.10 Enumerated parameters (E) 31 6.11 Index parameters (IX) 33 6.12 Client specified name parameters (CSN)

16、33 6.13 Input colour parameters (ICO, nICO) 33 6.14 Data record parameters (D) 33 7 Character substitution 34 8 Representation of CGI functions 35 8.1 Soliciting functions 36 8.2 Enumerated parameters 36 8.3 Functions not specified in ISO/IEC9636 36 8.3.1 DOMAIN RING 36 8.3.2 INTEGER PRECISION 37 8.

17、3.3 REAL PRECISION 37 8.3.4 INDEX PRECISION 38 8.3.5 COLOUR PRECISION 38 8.3.6 COLOUR INDEX PRECISION 38 8.3.7 VDC INTEGER PRECISION 38 8.3.8 VDC REAL PRECISION 38 8.3.9 CLIENT SPECIFIED NAME PRECISION 39 8.4 Encoding of matrices 39 9 Defaults 39 10 Classification and designation 40 Annex A (informa

18、tive) List of CGI Opcodes 41 Annex B (informative) List of escape sequences 51 Figure 1 The 7-bit code table 4 Figure 2 The 8-bit code table 4 Table 1 Opcodes and Response Opcodes of CGI Functions 8 Table 2 Huffman Code table for incremental mode 24 Table 3 C0 control set 30 Table 4 Character substi

19、tution 35ISO/IEC 9637-1:1994 (E) iv BSI 02-2000 Foreword ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of ISOorIEC participate in the develop

20、ment of International Standards through technical committees established by the respective organization to deal with particular fields of technical activity. ISOandIEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental,

21、 in liaison with ISOandIEC, also take part in the work. In the field of information technology, ISOandIEC have established a joint technical committee, ISO/IECJTC1. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an

22、International Standard requires approval by at least75% of the national bodies casting a vote. International Standard ISO/IEC9637-1 was prepared by Joint Technical Committee ISO/IECJTC1, Information technology, Sub-Committee SC24, Computer graphics and image processing, in collaboration with the Eur

23、opean Computer Manufacturers Association (ECMA) and the European Conference of Postal and Telecommunications Administration (CEPT). ISO/IEC9637 consists of the following parts, under the general title Information technology Computer graphics Interfacing techniques for dialogues with graphical device

24、s (CGI) Data stream binding: Part 1: Character encoding; Part 2: Binary encoding; Part 3: Clear text encoding. Annex A and Annex B of this part of ISO/IEC9637 are for information only.ISO/IEC 9637-1:1994(E) BSI 02-2000 1 Introduction 0.1 Purpose of the character encoding The character encoding of th

25、e Computer Graphics Interface (CGI) provides a data stream representation of the CGI function syntax intended for situations in which it is important to minimize the size of the encoded data or transmit the data through character-oriented communications services. The encoding uses compact representa

26、tion of data that is optimized for storage or transfer between computer systems. If minimizing the processing overhead is more important than data compaction, an encoding such as the binary encoding contained in ISO/IEC9637-2 may be more appropriate. 0.2 Objectives This encoding was designed with th

27、e following objectives: a) regular syntax: All CGI functions are encoded in a uniform way so that parsing the encoded data is simple; b) compactness: the encoding provides a highly compact data stream, suitable for systems with restricted storage capacity or transfer bandwidth; c) extensibility: the

28、 encoding allows for future extensions; d) transportability: the encoding is suitable for use with transport mechanisms designed for character-oriented data based on a standard national character set derived from ISO/IEC646. 0.3 Relationship to other International Standards The character encoding ha

29、s been developed in collaboration with the ISO/IECJTC1/SC2. The encoding conforms to the rules for code extension specified in ISO2022 in the category of complete coding system. The representation of character data in this part of ISO/IEC9637 follows the rules of ISO/IEC646 and ISO2022. For certain

30、functions, ISO/IEC9636 defines value ranges as being reserved for registration. The values and their meanings will be defined using the established registration procedures (see ISO/IEC9636-1). This encoding is based on that for the Computer Graphics Metafile ISO/IEC8632-2. Wherever possible, the opc

31、odes and parameter representations of CGM elements have been followed. 1 Scope This part of ISO/IEC9637 specifies a character encoding of the Computer Graphics Interface. For each of the functions specified in ISO/IEC9636 an encoding is specified. This encoding of the Computer Graphics Interface pro

32、vides a highly compact representation of the data, suitable for applications that require the data to be of minimum size and suitable for transmission with character-oriented transmission services. 2 Normative references The following standards contain provisions which, through reference in this tex

33、t, constitute provisions of this part of ISO/IEC9637. At the time of publication the editions indicated were valid. All standards are subject to revision, and parties to agreements based to this part of ISO/IEC9637 are encouraged to investigate the possibility of applying the most recent editions of

34、 the standards listed below. Members of ISOandIEC maintain registers of currently valid International Standards. ISO/IEC 646:1991, Information technology ISO 7-bit coded character set for information interchange. ISO 2022:1986, Information processing ISO 7-bit and 8-bit coded character sets Coded ex

35、tension techniques. ISO 2375:1985, Data processing Procedure for registration of escape sequences. ISO/IEC 6429:1992, Information technology Control functions for coded character sets. ISO 7942:1985, Information processing systems Computer graphics Graphical Kernel System (GKS) functional descriptio

36、n. ISO/IEC 8632-2:1992, Information technology Computer graphics Metafile for the storage and transfer of picture description information Part 2: Character encoding. ISO/IEC 9637-1:1994 (E) 2 BSI 02-2000 ISO/IEC 9636-1:1991, Information technology Computer graphics Interfacing techniques for dialogu

37、es with graphical devices (CGI) Functional specification Part 1: Overview, profiles and conformance. ISO/IEC 9636-2:1991, Information technology Computer graphics Interfacing techniques for dialogues with graphical devices (CGI) Functional specification Part 2: Control. ISO/IEC 9636-3:1991, Informat

38、ion technology Computer graphics Interfacing techniques for dialogues with graphical devices (CGI) Functional specification Part 3: Output. ISO/IEC 9636-4:1991, Information technology Computer graphics Interfacing techniques for dialogues with graphical devices (CGI) Functional specification Part 4:

39、 Segments. ISO/IEC 9636-5:1991, Information technology Computer graphics Interfacing techniques for dialogues with graphical devices (CGI) Functional specification Part 5: Input and echoing. ISO/IEC 9636-6:1991, Information technology Computer graphics Interfacing techniques for dialogues with graph

40、ical devices (CGI) Functional specification Part 6: Raster. ISO/IEC 9637-2:1992, Information technology Computer graphics Interfacing techniques for dialogues with graphical devices (CGI) Data stream binding Part 2: Binary encoding. ISO/IEC TR 9973:1988, Information processing Procedures for Registr

41、ation of Graphical Items. ECMA 96, Graphics Data Syntax for a multiple Workstation Interface. CEPT, Rev. of T/CD 6.1 Videotex Presentation Layer Data Syntax. 3 Notational conventions 3.1 7-Bit and 8-Bit code tables The bits of the bit combinations of the7-bit code are identified byb7,b6,b5,b4,b3,b2,

42、 andb1, whereb7 is the highest-order, or most-significant, bit andb1 is the lowest-order, or least-significant, bit. The bit combinations may be interpreted to represent integers in the range0 to127 in binary notation by attributing the following weights to the individual bits: In this part of ISO/I

43、EC9637 the bit combinations of a7-bit code are identified by notation of the form x/y, where x is a number in the range0 to7 and y is a number in the range0 to15. The correspondence between the notations of the form x/y and the bit combinations consisting of the bitsb7 tob1 is as follows: x is the n

44、umber represented byb7,b6, andb5 where these bits are given the weights4,2, and1 respectively; y is the number represented byb4,b3,b2, andb1 where these bits are given the weights8,4,2, and1 respectively. The notations of the form x/y are the same as those used to identify code table positions, wher

45、e x is the column number and y is the row number. A 7-bit code table consists of128 positions arranged in eight columns and sixteen rows. The columns are numbered0 to7 and the rows are numbered0 to15. Figure 1 shows a7-bit code table. An example illustrates the7-bit code: 1/11 refers to the bit comb

46、ination in column1, row11 of the code table, binary0011011. The bits of the bit combinations of the 8-bit code are identified by b8,b7,b6,b5,b4,b3,b2, andb1, whereb8 is the highest-order, or most-significant, bit andb1 is the lowest-order, or least-significant, bit. The bit combinations may be inter

47、preted to represent integers in the range0 to255 in binary notation by attributing the following weights to the individual bits: Using these weights, the bit combinations of the 8-bit code are interpreted to represent numbers in the range0 to255. Bit: b7 b6 b5 b4 b3 b2 b1 Weight: 64 32 16 8 4 2 1 Bi

48、t: b8 b7 b6 b5 b4 b3 b2 b1 Weight: 128 64 32 16 8 4 2 1ISO/IEC 9637-1:1994(E) BSI 02-2000 3 In this part of ISO/IEC9637 the bit combinations of an 8-bit code are identified by notation of the form xx/yy, where xx and yy are numbers in the range00 to15. The correspondence between the notations of the

49、 form xx/yy and the bit combinations consisting of the bitsb8 tob1 is as follows: xx is the number represented byb8,b7,b6, andb5 where these bits are given the weights8,4,2, and1 respectively; yy is the number represented byb4,b3,b2, andb1 where these bits are given the weights8,4,2, and1 respectively. The notations of the form xx/yy are the same as those used to identify code table positions, where xx is the column number and yy is the row number. An8-b