1、BRITISH STANDARD BS ISO/IEC 9637-2:1992 Implementation of ISO/IEC 9637-2:1992 Information technology Computer graphics Interfacing techniques for dialogues with graphical devices (CGI) Data stream binding Part 2: Binary encoding UDC 681.3.04(084):621.39BSISO/IEC9637-2:1992 This British Standard, hav
2、ing been prepared under the directionof the Information Systems Technology Standards Policy Committee, was publishedunder the authorityofthe Standards Boardand comes into effect on 15April1993 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference IST/31 Dr
3、aft for comment 91/65502 DC ISBN 0 580 22072 9 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 represen
4、ted: Department of Trade 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/IEC9637-2:1992 BSI 02-2000 i Contents Page Committees responsible Inside fr
5、ont cover National foreword ii Foreword iv Text of ISO/IEC 9637-2 1BSISO/IEC9637-2:1992 ii BSI 02-2000 National foreword This British Standard reproduces verbatim ISO/IEC9637-2:1992 and implements it as the UK national standard. This British Standard is published under the direction of the Informati
6、on Systems Technology 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 rela
7、ted international and European developments and promulgate them in the UK. NOTEInternational and European Standards, as well as overseas standards, are available from BSI Sales Department, BSI, Linford Wood, Milton Keynes, MK14 6LE. A British Standard does not purport to include all the necessary pr
8、ovisions of 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/IECtitle
9、 page, pagesii toiv, pages1 to46and 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/IEC9637-2:1992(E) ii BSI 02-2000 Contents Page Foreword iv Introduction 1 1 Scop
10、e 2 2 Normative References 2 3 Definitions 3 4 Overall structure 3 4.1 General form of the data stream 3 4.2 General structure of the Binary Encoding 3 4.3 Encoding functions 4 4.3.1 General structure of the representation header 5 4.3.2 Basic short-form representation header 5 4.3.3 Basic long-form
11、 representation header 5 4.3.4 Extended-form representation header 6 4.4 Encoding parameter data 7 4.5 Encoding function response data 8 4.5.1 Structure of response representations 8 5 Binary Encoding primitive data forms 8 5.1 Signed Integer 8 5.1.1 Signed Integer at 8-bit precision 8 5.1.2 Signed
12、Integer at 16-bit precision 9 5.1.3 Signed Integer at 24-bit precision 9 5.1.4 Signed Integer at 32-bit precision 9 5.2 Unsigned Integer 9 5.2.1 Unsigned Integer at 8-bit precision 9 5.2.2 Unsigned Integer at 16-bit precision 9 5.2.3 Unsigned Integer at 24-bit precision 10 5.2.4 Unsigned Integer at
13、32-bit precision 10 5.3 Octet 10 5.4 Fixed Point Real 10 5.4.1 Fixed Point Real at 32-bit precision 10 5.4.2 Fixed Point Real at 64-bit precision 10 5.4.3 Values of Fixed Point Real 11 5.5 Floating Point Real 11 6 Representation of abstract parameter data types 11 6.1 Special Binary Encoding rules 1
14、4 6.1.1 Encoding the precision functions 14 6.1.1.1 Binary Encoding precision functions 14 6.1.2 Encoding strings, fixed strings, and data records 16 6.1.2.1 Encoding data record contents 17 6.1.2.2 String parameters and character sets 17 6.1.3 Encoding input functions 18 6.1.4 INHERITANCE FILTER en
15、umerated values 18 6.1.5 Encoding point lists 20 6.1.6 Encoding transformation matrix components 20 6.1.7 Encoding local colour precision 20 6.1.7.1 Encoding CELL ARRAY and PATTERN TABLE local colour precision 20 6.1.7.2 Encoding PIXEL ARRAY local colour precision 21 6.1.8 Colour specifier lists 21
16、6.1.8.1 Encoding colour specifier lists 22ISO/IEC9637-2:1992(E) BSI 02-2000 iii Page 6.1.8.2 Encoding lists of input colour values and local colour precision 22 6.1.9 Encoding PATTERN TABLE and INQUIRE PATTERN colour specifiers 22 7 Representation of each function and response 23 7.1 Opcode assignme
17、nts 23 7.1.1 Class code assignments 23 7.1.2 Function id code assignments 24 8 Defaults 39 9 Classification and designation 40 9.1 Conformance 40 Annex A (normative) Algorithms and rules for class code assignment 41 Annex B (informative) Encoding examples 42 Figure 1 Bit numbering for octets and wor
18、ds 4 Figure 2 Format of a basic short-form representation header 5 Figure 3 Format of a basic long-form representation header 6 Figure 4 Format of an extender header 7 Table 1 Binary data structure 4 Table 2 Representation of basic data types 12 Table 3 Representation of abstract data types 13 Table
19、 4 Data types and matching precision functions 14 Table 5 Data type index assignments within data records 17 Table 6 Inheritance filter selection list enumerated values 18 Table 7 List of function/response class codes 23 Table 8 List of function/response representation opcodes 24ISO/IEC9637-2:1992(E
20、) 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 ISO or IEC participate in the development of International Standar
21、ds through technical committees established 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 IE
22、C, also take part in the work. In the field of information technology, ISO and IEC 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 International Standard
23、requires approval by at least75% of the national bodies casting a vote. International Standard ISO/IEC9637-2 was prepared by Joint Technical Committee ISO/IECJTC1, Information technology. ISO/IEC 9637 consists of the following parts, under the general title Information technology Computer graphics I
24、nterfacing techniques for dialogues with graphical devices (CGI) Data stream binding Part 1: Character encoding; Part 2: Binary encoding. Annex A forms an integral part of this part of ISO/IEC9637.Annex B is for information only.ISO/IEC9637-2:1992(E) BSI 02-2000 1 Introduction Purpose The Binary Enc
25、oding of the Computer Graphics Interface (CGI), ISO/IEC9636, provides a data stream representation of the CGI function syntax that can be optimized for speed of generation and interpretation, while still providing a standard means of interchange among computer systems. The encoding uses binary data
26、formats that are more similar to the data representations used within computer systems than the data formats of the other encodings. Some of the data formats may exactly match those of some computer systems. On most computer systems processing requirements for the Binary Encoding will be substantial
27、ly lower than for the other encodings. In cases where a computer systems architecture does not match the standard formats used in the Binary Encoding, and where absolute minimization of processing requirements is critical, and where interchange among dissimilar systems does not matter, it may be mor
28、e appropriate to use a private encoding, conforming to the rules specified in ISO/IEC9636-1. Objectives This encoding has the following features: a) Partitioning of parameter lists: function/response representations are coded in the Binary Encoding by one or more partitions (see clause4); the first
29、(or only) partition of a representation contains the opcode (class code and id code); b) Alignment of function representations and response representations: every function/response representation begins on a 16-bit boundary. Alignment of representations which follow partitions that require an odd nu
30、mber of 8-bit entities may require a partition to be padded with an 8-bit entity with all bits zero; c) Uniformity of format: all function representations and response data records have an associated parameter length value. As a result, it is possible to ignore function representations which are not
31、 supported by the interpreter; d) Efficiency of encoding parameter data: parameter data such as coordinates, indexes and colours are encoded as one or more 8-bit entities. The precision of every parameter is determined by the appropriate default precision or as set by a precision setting CGI functio
32、n; e) Extensibility: the arrangement of opcode class and id values has been designed to allow future growth; f) Format of real data: real numbers are encoded using either IEEE floating point representation or a fixed-point representation; g) Run length encoding option: if many adjacent colours have
33、the same value, efficient encoding is possible. For each run a cell count is specified followed by the colour (or colour index); h) Packed list encoding option: if adjacent colours do not have the same value, bit-stream lists are provided in which the values are packed as closely as possible; i) Enc
34、oding of soliciting functions: the assignment of opcodes to functions which require a response has been designed so that all such functions can be recognized by a CGI interpreter; j) Response Data: responses to soliciting functions have been assigned different opcodes from their associated solicitin
35、g functions. However, the response opcode can be derived in a straightforward manner from the soliciting function opcode; k) Lists of data: there is a standard technique for representing lists of any type of data (with a few specific exceptions); Relationship to other standards This encoding is guid
36、ed by the same objectives as the Computer Graphics Metafile Binary Encoding, ISO/IEC8632-3:1992. For each CGI function which is identical in both semantics and parameterization to a CGM element, the encoding will be identical. That is, the opcodes will be identical and the parameters will use the sa
37、me data type and appear in the same order. The extension mechanism defined in this encoding is also compatible with the CGM Binary Encoding. The floating point representation of real data in this part of the Standard is that in ANSI/IEEE754:1986. The representation of character data in this part of
38、the Standard follows the rules of ISO646 and ISO2022.ISO/IEC9637-2:1992(E) 2 BSI 02-2000 For certain functions and response data, the CGI defines parameter value ranges as being reserved for registration. The values and their meanings will be defined using the procedures established in ISOTR9973. 1
39、Scope This part of ISO/IEC 9637 specifies a Binary Encoding of the Computer Graphics Interface (CGI) data stream. For each of the function syntaxes in clause5 and clause6 of ISO/IEC9636-2, ISO/IEC9636-3, ISO/IEC9636-4, ISO/IEC9636-5, and ISO/IEC9636-6, an encoding is specified in terms of an opcode
40、and a sequence of parameters of specified data types. For each of these data types, an explicit representation in terms of bits, 8-bit and 16-bit entities is specified. For some data types, the exact representation depends on a type and/or precision for the data as used in the data stream. The Binar
41、y Encoding of the Computer Graphics Interface data stream will, in many circumstances, reduce the effort required to generate and interpret the data stream as compared to other encodings. 2 Normative references The following standards contain provisions which, through reference in this text, constit
42、ute provisions of this part of ISO/IEC9637. At the time of publication, the editions indicated were valid. All standards are subject to revisions, and parties to agreements based on this part of ISO/IEC9637 are encouraged to investigate the possibility of applying the most recent editions of the sta
43、ndards listed below. Members of IEC and ISO 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 Code extension
44、 techniques. ISO/IEC 7942:1985/Amd.1:1991, Information processing systems Computer graphics Graphical Kernel System (GKS) functional description Amendment 1. ISO 8632-1:1992, Information technology Computer graphics Metafile for the storage and transfer of picture description information Part1:Funct
45、ional specification. ISO 8632-3:1992, Information technology Computer graphics Metafile for the storage and transfer of picture description information Part3:Binary encoding. ISO/IEC 9636-1:1991, Information technology Computer graphics Interfacing techniques for dialogues with graphical devices(CGI
46、) 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, Information technology Computer graphic
47、s 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: Segments. ISO/IEC 9636-5:1991, I
48、nformation 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 graphical devices(CGI) Functional speci
49、fication Part 6: Raster. ISO/IEC 9637-1:1992, Information technology Computer graphics Interfacing techniques for dialogues with graphical devices(CGI) Data stream binding Part 1: Character encoding. ISO/IEC TR 9973:1988, Information technology Computer graphics Procedures for registration of graphical items. ANSI/IEEE 754, Standard for Binary Floating Point Arithmetic. ISO/IEC9637-2:1992(E) BSI 02-2000 3 3 Definitions 3.1 representation portion
