ISO/IEC 9637-2:1992

INTERNATIONAL
ISO/IEC
STANDARD
9637-2
First edition
1992-I Z-01
Information technology - Computer
graphics - Interfacing techniques for
dialogues with graphical devices (CGI) -
Data stream binding -
Part 2:
Binary encoding
Technologies de /‘information - lnfographie - Interfaces pour
l’infographie - Interface du flux de donnkes CGI -
Partie 2: Codage binaire
Reference number
lSO/IEC 9637-2:1992(E)
ISO/IEC 963702:1992 (E)
Page
CONTENTS
Foreword , . . . , . . . . . . . . . . . , . . . . . . . . . . . . . iv
V
Introduction . . , . . . . . . . . . . . . . . . . . e . . . . . . .
1 Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Normative References . . . . . . . . . . 0 . . . . . . . . . . . .
3 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . 4
. . . . .I. Y . . . . . 5
4 Overall structure
4.1 General form of the data’s&&& . . a . . . . .I 5
4.2 General structure of the Binary Endoding’ . . . . . . . D . .
. . . . 7
4.3 Encoding functions
4.3.1 General structure’of the ~epresen;a;ion*h~a~er . . . .
4.3.2 Basic short-form representation header . . . . . . . .
4.3.3 Basic long-form representation header . . . . . . . .
4.3.4 Extended-form representation header . . . . . s . . .
4.4 Encoding parameter data . . . . . . . . . . . . . . . . . . .
4.5 Encoding function response data . . . . . . . . . . . . . W .
4.5.1 Structure of response representations . . . . . . . .
5 Binary Encoding primitive data forms . . . . . . .
5.1 Signed Integer . .
5.1.1 Signed Integer at’8ibit’predision’ . .
5.1.2 Signed Integer at 16-bit precision . .
5.1.3 Signed Integer at 24--bit precision . .
5.1.4 Signed Integer at 32-bit precision . . . , . . 3 . . l
5.2 Unsigned Integer .
5.2,1 Unsigned Integei &‘8~bit’pre&sion’ .
5.2.2 Unsigned Integer at 16-bit precision .
5.2.3 Unsigned Integer at 24-bit precision .
5.2.4 Unsigned Integer at 3%bit precision . 16
5.3 Octet . . . . . . . . . . . . . . a. .
5.4 Fixed Point Real’ .
5.4.1 Fixed PointReal &‘8~-bit precision .
5.4.2 Fixed Point Real at 64--bit precision . 17
5.4.3 Values of Fixed Point Real . . . , . . 18
5.5 Floating Point Real . . . . . . . . . . . . . 18
o ISO/IEC 1992
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ii
@lSO/IEC ISO/IEC 963702:1992 (E)
6 Representation of abs tract parameter data types l . . I . . . . .
6.1 Special Binary Encoding rules . . . . . . . . . . . . . . . .
6.1.1 Encoding the precision functions . . . . . . . . . . l
6.1.1.1 Binary Encoding precision functions
6.1.2 Encoding strings, fixed strings, and data records. . .
6.1.2.1 Encoding data record contents .
6.1.2.2 String parameters and character sets .
6.1.3 Encod ng input functions .
6.1.4 INHER TANCE FILTER enumerated values .
6.1.5 Encod ng point lists .
6.1.6 Encod ng transformation matrix components .
6.1.7 Encod ng local colour precision .
6.1.7.1 Encoding CELL ARRAY and PATTERN TABLE
local colour precision .
6.1.7.2 Encoding PIXEL ARRAY local colour precision . .
6.1.8 Colour specifier lists . . . . . . . . . . . I . . . .
6.1.8.1 Encoding colour specifier lists 37
6.1.8.2 Encoding lists of input colour values’and’lock’ 37
colour precision . . . . . . . . . . . . . . . . 38
6.1.9 Encoding PATTERN TABLE and INQUIRE PATTERN
colour specifiers. . . . . . . . . . . . . . . . . . . 38
7 Representation of each function and response . 39
7.1 Qpcode assignments . 39
7.1.1 Class code assignments . 39
7.1.2 Function id code assignments .
8 Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
9 Classification and designation . 63
9.1 Conformance . 63
A Algorithms and rules for class code assignment . . . . . . . I . . 64
B Encoding examples . . . . . . . . . . . . . . . . . . . . . . . 66
iii
ISO/IEC 963702:1992 (E) @lSO/IEC
Foreword
IS0 (the International Organization for Standardization) and IEC (the Inter-
national Electrotechnical Commission) form the specialized system for
worldwide standardization. National bodies that are members of IS0 or
IEC participate in the development of International Standards through
technical committees established by the respective organization to deal
with particular fields of technical activity. IS0 and IEC technical com-
mittees collaborate in fields of mutual interest. Other international organ-
izations, governmental and non-governmental, in liaison with IS0 and IEC,
also take part in the work.
In the field of information technology, IS0 and IEC have established a joint
technical committee, lSO/IEC JTC 1. Draft International Standards adopted
by the joint technical committee are circulated to national bodies for vot-
ing. Publication as an International Standard requires approval by at least
75 % of the national bodies casting a vote.
International Standard lSO/IEC 9637-2 was prepared by Joint Technical
Committee lSO/IEC JTCI, Information technology.
lSO/IEC 9637 consists of the following parts, under the general title In-
formation technology
- Computer graphics - Interfacing techniques for
dialogues with graphical devices (CGI) - Data stream binding
- Part I: Character encoding
- Part 2: Binary encoding
Annex A forms an integral part of this part of lSO/IEC 9637. Annex B is for
information only.
@lSO/IEC
ISO/IEC 963792:1992 (E)
Introduction
Purpose
The Binary Encoding of the Computer Graphics Interface (CGI), ISO/IEC 9636,
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 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
substantially lower than for the other encodings.
In cases where a computer system’s 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 more appropriate to use a private encoding,
conforming to the rules specified in ISO/IEC 9636-l.
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 clause
the first (or only) partition of a representation contains the
;
4)
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 number 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
As a result, it is
records have an associated parameter length value.
possible to ignore function representations which are not 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 CC1
function;
@lSO/IEC
ISO/IEC 963702:1992 (E)
e) Extensibility: the arrangement of opcode class and id values has been
designed to allow future growth;
real numbers are encoded using either IEEE
f) Format of real data:
floating point representation or a fixed-point representation;
g) Run length encoding option: if many adjacent colours have 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) Encoding 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;
responses to soliciting functions have been assigned
j) Response Data:
different opcodes from their associated soliciting functions.
the response opcode can be derived in a straightforward
However,
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 guided by the same objectives as the Computer Graphics
For each CGI function which
Metafile Binary Encoding, ISO/IEC 8632-39992.
is identical in both semantics and parameterization to a CGM element, the
That is, the opcodes will be identical and the
encoding will be identical.
parameters will use the same 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/IEEE 7544986.
The representation of character data in this part of the Standard follows
the rules of IS0 646 and IS0 2022.
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 IS0 TR 997%
vi
I NTERNAT I ONAL STANDARD olSo’lEC
ISO/IEC 963702:1992 (E)
Information technology - Computer graphics -
Interfacing techniques for dialogues with graphical
devices (CGI)
- Data stream binding -
Part 2: 9
Binary encoding
1 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 clause 5
and clause 6 of ISO/IEC 9636-2, ISOAEC 9636-3, ISO/IEC 9636-4, ISO/IEC
9636-5, and ISO/IEC 9636-6, an encoding is specified in terms of an opcode and
a sequence of parameters of specified data types. For each of these data
an explicit representation in terms of bits, 8-bit and 16-bit entities
types 9
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 Binary 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.
ISOAEC 963792:1992 (E) @lSO/IEC
2 Normative references
through reference in this text,
The following standards contain provisions which,
At the time of publication,
constitute provisions of this part of ISO/IEC 9637.
All standards are subject to revisions, and
the editions indicated were valid.
of ISO/IEC 9637 are encouraged to
parties to agreements based on this part
investigate the possibility of applying the most recent editions of the standards
Members of IEC and IS0 maintain registers of currently valid
listed below.
International Standards.
ISO/IEC 646 : 1991, Information technology - IS0 7-bit coded character set for information
interchange.
IS0 2022 : 1986, Information processing - IS0 7-bit and &bit coded character sets - Code
extension techniques.
ISO/IEC 7942:1985/Amd.l:1991, Information processing systems - Computer graphics -
Graphical Kernel System (GKS) functional description - Amendment 1
IS0 8632-l : 1992, Information technology - Computer graphics - Metafile for the storage and
transfer of picture description information - Part 1: Functional specification.
IS0 8632-3 : 1992, lnformation technology - Computer graphics - Metafile for the storage and
transfer of picture description information - Part 3: Binary encoding.
ISO/IEC 9636-l : 1991, Information technology - Computer graphics - Interfacing techniques
for dialogues with graphical devices(CG1) - Functional specification - Part 1: Overview,
profiles and conformance.
ISO/IEC 9636-2 : 1991, Information technology - Computer graphics - Interfacing techniques
for dialogues with graphical devices(CG1) - Functional specification - Part 2: Control.
ISO/IEC 9636-3 : 1991, lnformation technology - Computer graphics - Interfacing techniques
for dialogues with graphical devices(CG1) - Functional specification - Part 3: Output.
ISO/IEC 9636-43991, Information technology - Computer graphics - interfacing techniques
for dialogues with graphical devices(CG1) - Functional specification - Part 4: Segments.
Information technology - Computer graphics - interfacing techniques
ISO/IEC 9636-52991,
for dialogles with graphical devices(CG1) - Functional specification - Part 5: Input and echoing.
ISOAEC 963792:1992 (E)
@lSO/IEC
Normative References
ISO/ IEC 9636-6 : 1991, lnformation technology - Computer graphics - Interfacing techniques
for dialogues with graphical devices(CG1) - Functional specification - Part 6: Raster.
ISO/IEC 9637-l : 1992, Information technology - Computer graphics - interfacing techniques
for dialogues with graphical devices(CG1) - 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 Flouting Point Arithmetic.

3 Definitions
Portion of a binary-encoded function or response representation
3.1 representation:
class plus function/response id) and
that contains the opcode (function/response
...