EN 28632-2:1994

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Information technology - Computer graphics - Metafile for the storage and transfer of picture description information - Part 2: Character encoding (ISO/IEC 8632-2:1992)Informationstechnik - Graphische Datenverarbeitung - Datei für die Speicherung und die Übertragung von BildinformationTechnologies de l'information - Infographie - Métafichier de stockage et de transfert des informations de description d'Information technology - Computer graphics - Metafile for the storage and transfer of picture description information -35.140Computer graphicsICS:Ta slovenski standard je istoveten z:EN 28632-2:1994SIST EN 28632-2:1997en01-december-1997SIST EN 28632-2:1997SLOVENSKI
STANDARD
INTERNATIONAL STANDARD ISOAEC 8632-2 Second edition 1992-10-01 ------.-.- ------- _ -__._._-. _____ -_ _ --_- - .--- ---------- -----.-. -_ .--.------ - -. _-.--.--.---. .---- -_----- ---_- .---. -__-_.- .---. ---__.--------.----I_--- _.- Information technology - Computer graphics - Metafile for the storage and transfer of picture description information - Part 2: Character encoding Technologies de I’hforrnatior~ ---- Infographie -- M&fichier de stockage et de fr-ansfert des ir~formations de description d’images - Pat-tie 2: Codaqe des cat-act&-es \ Reference number ISCM EC 8632-2: 1992(E) SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) CONTENTS 1 Scope. . . . . . . . . . . . . . . . . . . . . . 2 Normative references . . . . . . . . . . . . . . . . . 3 Notational conventions . 7-Bit and S-Bit code tables . . . . . . . . . . . . . . 3.1 . . . . . . . . . . 3.2 Code extension techniques vocabulary l . . . . . . . . . . 3.2.1 CO sets . . . v . . . . . . . . . . . . . 3.2.2 Cl sets . . . . . . . . . . . . . . . . . 3.2.3 G-sets . . . . . . . . . . . . . . . . . . 4 Entering and leaving the metafile environment . . . Q . . . . . 4.1 Implicitly entering the metafile environment . . . . . . . . 4.2 Designating and invoking the CGM coding environment from IS0 2022 5 Method of encoding opcodcs . 5.1 Encoding technique of the basic opcode set 5.2 Extension mechanism . 5.3 Opcode assignments . 6 Method of encoding parameters . . . . . 6.1 Basic format . . . . . . . . . 6.2 Bitstream format . . . . . . . . 6.3 Coding integers . . . . . . . . 6.4 Coding real numbers . ’ . . . . . 6.5 Coding VDCs and points . . . . . 6.6 Coding point list parameters . . . . 6.6.1 Displacement mode . . . . . 6.6.2 Incremental mode . . . . . 6.6.3 Incremental mode encoding . . 6.7 Colour specifiers . . . . . . . . 6.8 Colour lists * 6.8.1 Normal format*(cdding t&10) . 6.8.2 Bitstream format (coding type=l) 6.8.3 Runlength format (coding type=2) . . . . . . . . . . . . . . . . . . . 6.8.4 Runlength bitstream format (coding type=3) 6.8.5 Examples . . . . . . . . . . . 6.9 String parameters . . . . 6.9.1 Overall string iaramkter format . . . . . . . . . . . . . . . . . . . * a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . . . . 6.9.2 Bit combinations permitted within string parameters of text elements 6.9.3 CO control within string parameters . . . . . . . . . . 6.9.4 Using G-sets in string parameters . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . e . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . . . . . . . . . . l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 7 7 7 14 14 15 16 16 18 18 18 19 22 23 24 25 25 25 25 26 27 27 27 28 28 0 lSO/lEC 1992 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. ISO/IEC Copyriigkt Office l Case postale 56 l CH-1211 Genkve 20 l Switzerland Printed in Switzerland 11 SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 6.10 6.11 6.12 6.13 6.14 6.15 6.16 6.17 Enumerated parameters . . . . . . Index parameters . . . . . . . . Data record parameters . . . . . - Coding VCs and viewport point parameters Name parameters . v . . . . Compressed bitstream operands . Structured data record operands . Glyphmapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Character substitution . . . . . . 8 Representation of each element . . . 8.1 Delimiter elements . . . . . 8.1.1 81.2 8.1.3 8.1.4 8.15 8.1.6 8.1.7 8.1.8 8.1.9 8.1.10 8.1.11 8.1.12 8.1.13 8.1.14 8.1.15 8.1.16 8.1.17 BEGINMETAFILE . . ENDMETAFILE . . . BEGINPICTURE . . . BEGIN PICTURE BODY . ENDPICTURE . l . . BEGINSEGMENT . . . ENDSEGMENT . . e BEGINFIGURE . . . ENDFIGURE . . . . BEGIN PROTECTION REGION END PROTECTION REGION . BEGIN COME’OUNDLINE . . END COMPOUNDLINE . . . BEGIN COMPOUND TEXT PATH END COMPOUND TEXT PATH BEGINTILE ARRAY . . . . ENDTILE ARRAY . . . . 8.2 Metafile descriptor elements . . . 8.2.1 METAFILE VERSION . 8.2.2 METAFILE DESCRIPTION . 8.2.3 VDCTYPE . . . . . . 8.2.4 INTEGER PRECISION . . 8.2.5 REAL PRECISION . . . . 8.2.6 INDEXPRECISION . . . 8.2.7 COLOUR PRECISION 8.2.8 COLOUR INDEX PRECISION 8.2.9 MAXIMUM COLOUR INDEX 8.2.10 COLOUR VALUE EXTENT . 8.2.11 METAFILE ELEMENT LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2.12 METAFILE DEFAULTS REPLACEMENT 8.2.13 FONTLIST . . . . . . . . . . 8.2.14 CHARACTER SET LIST . . . . . . 8.2.15 CHARACTER CODING ANNOUNCER . 8.2.16 NAME PRECISION 8.2.17 MAXIMUM VDC EXTENT . . . . . 8.2.18 SEGMENT PRIORITY EXTENT. : : : 8.2.19 COLOUR MODEL . . . . . . . . 8.2.20 COLOUR CALIBRATION . . . . . 8.2.2 1 FONT PROPERTIES . . . . . . . 8.2.22 GLYPH MAPPING . . . . . 8.2.23 SYMBOL LIBRARY LIST’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . * . . . . . . . . . . . . . . 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l . . . . . . . . . . . . . . . . . . . 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 29 29 29 30 30 30 30 31 33 35 35 35 35 35 35 35 36 36 36 36 36 36 36 36 36 36 37 38 38 38 38 38 38 39 39 40 40 40 40 41 41 41 42 42 42 42 42 42 44 46 47 . . . 111 SIST EN 28632-2:1997

ISO/IEC8632=2:1992(E) 8.3 Picture descrbtor elements . . . . . . . . . . . . . . . . . . . . 48 8.3.1 8.3.2 8.3.3 8.3.4 8.3.5 8.3.6 8.3.7 8.3.8 8.3.9 8.3.10 8.3.11 8.3.12 8.3.13 8.3.14 8.3.15 8.3.16 8.3.17 8.3.18 8.3.19 SCALiNG MODE COLOUR SELECTION-MODE . 48 LINE WIDTH SPECIFICATION MODE . 48 . 48 MARKER SIZE SPECIFICATION MODE . 48 EDGE WIDTH SPECIFICATION MODE . 48 VDCEXTENT . 49 BACKGROUND COLOUR . 49 DEVICE VIEWPORT . 49 DEVICE VIEWPORT SPECIFICATION MODE . 49 DEVICE VIEWPORT MAPPING . 49 LINE REPRESENTATION . 50 MARKER REPRESENTATION . 50 TEXT REPRESENTATION . 50 FILL REPRESENTATION . 5 1 EDGE REPRESENTATION . 5 1 INTERIOR STYLE SPECIFICATION MODE . 52 LINE AND EDGE TYPE DEFINITION . 52 HATCH STYLE DEFINITION . 52 GEOMETRIC PATTERN DEFINITION . 53 r.4 8.4 Control elements . 34 8.4.1 VDC INTEGER PRECISION . 54 8.4.2 VDC REAL PRECISION . 54 8.4.3 AUXILIARY COLOUR . 55 8.4.4 TRANSPARENCY . 55 8.4.5 CLIPRECTANGLE . 55 8.4.6 CLIP INDICATOR . 55 8.4.7 LINE CLIPPING MODE . 55 8.4.8 MARKER CLIPPING MODE . 56 8.4.9 EDGE CLIPPING MODE . 56 8.4.10 NEWREGION . 56 8.4.11 SAVE PRIMITIVE CONTEXT . 56 8.4.12 RESTORE PRIMITIVE CONTEXT . 56 8.4.13 PROTECTION REGION INDICATOR . 56 8.4.14 GENERALIZED TEXT PATH MODE . 57 8.4.15 MITRELIMIT . 57 8.4.16 TRANSPARENT CELL COLOUR . 57 8.5 Graphical primitive elements . 58 8.5.1 POLYLINE . 58 8.5.2 DISJOINT POLYLINE . 58 8.5.3 POLYMARKER . 58 8.5.4 TEXT. . 58 8.5.5 RESTRICTED TEXT . 58 8.5.6 APPENDTEXT . 59 8.5.7 POLYGON . 59 8.5.8 POLYGONSET . 59 8.5.9 CELLARRAY . 59 8.5.10 GENERALIZED DRAWING PRIMITIVE . 6 1 8.5.11 RECTANGLE . 61 8.5.12 CIRCLE . 61 8.5.13 CIRCULAR ARC 3 POINT . 61 8.5.14 CIRCULAR ARC 3 POINT CLOSE . 61 8.515 CIRCULAR ARC CENTRE . 62 SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 8.5.16 8.5.17 8.5.18 8.5.19 8.5.20 8.5.21 8.5.22 8.5.23 8.5.24 8.5.25 8.5.26 8.5.27 8.5.28 8.5.29 CIRCULAR ARC CENTRE CLOSE . ELLIPSE . . . . . . . . . . ELLIPTICAL ARC . . . . . . . ELLIPTICAL ARC CLOSE . . . . CIRCULAR ARC CENTRE REVERSED CONNECTINGEDGE . . . . . HYPERBOLIC ARC . . . . . . PARABOLIC ARC . . . . . . . NON-UNIFORM B-SPLINE . . . . NON-UNIFORM RATIONAL B-SPLINE POLYBEZIER . . . . . POLYSYMBOL . . . . BITONALTILE . . . . TILE . . . . . . . . 8.6 Attribute elements . . . . . . 8.6.1 8.6.2 8.6.3 8.6.4 8.6.5 8.6.6 8.6.7 8.6.8 8.6.9 8.6.10 8.6.11 8.6.12 8.6.13 8.6.14 8.6.15 8.6.16 8.6.17 8.6.18 8.6.19 8.6.20 8.6.21 8.6.22 8.6.23 8.6.24 8.6.25 8.6.26 8.6.27 8.6.28 8.6.29 8.6.30 8.6.3 1 8.6.32 8.6.33 8.6.34 8.6.35 8.6.36 8.6.37 8.6.38 LINEBUNDLEINDEX . . LINETYPE . . . . . . LINE WIDTH . . . . . LINECOLOUR . . . . . MARKER BUNDLE INDEX . MARKERTYPE . . . . MARKERSIZE . . . . . MARKERCOLOUR . . TEXTBUNDLEINDEX . . TEXTFONTINDEX . . . TEXTPRECISION . . . . CHARACTER EXPANSION FACTOR CHARACTERSPACING . . . . . TEXT COLOUR CHARACTER HEIGHT . . . . . . . . CHARACTERORIENTATiON . . . TEXT PATH TEXT ALIGNME& . . . . . . . . o . CHARACTERSETINDEX . . . . ALTERNATE CHARACTER SET INDEX FILLBUNDLEINDEX . INTERIOR STYLE . FILL COLOUR . HATCH INDEX . PATTERN INDEX . EDGEBUNDLEINDEX . EDGE TYPE . EDGE WIDTH . EDGE COLOUR . EDGE VISIBILITY FILLREFERENCE POiNT . . . . . PATTERN TABLE . PATTERN SIZE . COLOUR TABLE . ASPECTSOURCEFLAGS . PICK IDENTIFIER . LINE CAP . LINE JOIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 . 62 . 62 . 63 . 63 . 63 . 63 . 63 . 64 . 64 . 64 . 65 . 65 . 66 . 67 . 67 . 67 . 67 0 67 . 67 . 67 . 68 . 68 . 68 . 68 . 68 . 68 . 69 . 69 . 69 . 69 . 69 . 69 . 70 . 70 . 70 . 70 . 71 . 71 . 71 . 71 . 71 . 72 . 72 . 72 . 72 . 72 . 72 . 73 . 73 . 74 . 74 . 74 V SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 8.6.39 8.6.40 8.6.41 8.6.42 8.6.43 8.6.44 8.6.45 8.6.46 8.6.47 8.6.48 8.6.49 8.6.50 8.6.5 1 LINE TYPE CONTINUATION LINE TYPE INITIAL OFFSET TEXT SCORETYPE . . l RESTRICTED TEXT TYPE . INTERPOLATED INTERIOR EDGECAP . . . . . . EDGEJOIN . . . . . . EDGE TYPE CONTINUATION EDGE TYPE INITIAL OFFSET SYMBOL LIBRARY INDEX SYMBOLCOLOUR l . SYMBOLSIZE . . . . SYMBOL ORIENTATION 8.7 Escape elements . . . . . . 8.7.1 ESCAPE . . e . . . 8.7.2 DOMAINRING . . . 8.8 External elements . . . . . 8.8.1 MESSAGE . . . . . 8.8.2 APPLICATION DATA . 8.9 Segment elements . . . . . 8.9.1 COPY SEGMENT . . . 8.9.2 INHERITANCE FILTER . 8.9.3 CLIP INHERITANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.9.4 SEGMENT TRANSFORMATION 8.9.5 SEGMENT HIGHLIGHTING 8.9.6 SEGMENT DISPLAY PRIORITY* 8.9.7 SEGMENT PICK PRIORITY . 9 Defaults . . . . . . . . . . . . 10 Conformance . . . . . . . . . . A Formal grammar . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l . . . . . . . . . . * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l . . . . . . . . . . . . . * . . . . . . . . . . . . . . . . 74 75 75 75 75 76 76 76 77 77 77 77 77 78 78 78 79 79 79 80 80 80 82 82 82 83 83 84 85 86 vi SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Foreword IS0 (the International Organization for Standardization) and IEC (the International 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 committees collaborate in fields of mutual interest. Other international organizations, 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, ISOIIEC JTC 1. 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 least 75 % of the national bodies casting a vote. International Standard ISOIIEC 8632-2 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology. This second edition cancels and replaces the first edition (IS0 8632-2: 1987), which has been technically revised. ISOIIEC 8632 consists of the following parts, under the general title Information technology - Computer graphics -Metafile for the storage and transfer of picture description information : Part I : Functional specijkation Part 2: Character encoding Part 3: Binary encoding Part 4: Clear text encoding Annex A forms an integral part of this part of ISO/IEC 8632. vii SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Introduction 0.1 Purpose of the character encoding The Character Encoding of the Computer Graphics Metafile (CGM) provides a representation of the Metafile syntax intended for situations in which it is important to minimize the size of the metafile or transmit the metafile through character-oriented communications services. The encoding uses compact representation 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/IEC 8632-3 may be more appropriate. If human readability is the most important criterion, an encoding such as the Clear Text Encoding in ISO/IEC 8632-4 may be more appropriate. 0.2 Objectives This encoding was designed with the following objectives: a> regular syntax: All elements of the metafile should be encoded in a uniform way so that parsing the metafile is simple; b) compactness: The encoding should provide a highly compact metafile, suitable for systems with restricted storage capacity or transfer bandwidth; C> extensibility: the encoding should allow for future extensions; d) transportability: the encoding should be suitable for use with transport mechanisms designed for character-oriented data based on a standard national character set derived from ISO/IEC 646. 0.3 Metafile characteristics Each CGM command follows a simple regular syntax. Thus, new commands can be added in a future revi- sion of ISO/IEC 8632 such that existing CGM interpreters can recognize (and ignore) the new commands Also, new operands can be added to existing commands in the future revision of the standard such tha existing CGM interpreters can recognize (and ignore) the additional operands. Each CGM operand follows a simple regular syntax. Operands are variable in length. This permits smal values to be represented by the smallest number of bytes. . . . Vlll SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Metafile characteristics Introduction A certain range of operand values of standard commands have been reserved for private use; the remaining range is either standardized or reserved for future standardization. 0.4 Relationship to other International Standards The Character Encoding has been developed in collaboration with the IS0 subcommittee responsible for character sets and coding, ECMA, and CEPT. The encoding conforms to the rules for code extension specified in IS0 2022 in the category of complete coding system. The representation of character data in this part of ISO/IEC 8632 follows the rules of ISO/IEC 646 and IS0 2022. For certain elements, the CGM defines value ranges as being reserved for registration. The values and t.he.ir meanings will be defined using the established procedures (see ISO/IEC 8632-1, sub-clause 4.12.) 1x SIST EN 28632-2:1997

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INTERNATIONAL STANDARD ISO/IEC 8632-2: 1992 (E) Information technology - Computer graphics - Metafile for the storage and transfer of picture description information - Part 2 : Character encoding 1 Scope This part of ISO/IEC 8632 specifies a character encoding of the Computer Graphics Metafile. For each of the elements specified in ISO/IEC 8632-1 an encoding is specified. This encoding of the Computer Graphics Metafile provides a highly compact representation of the metafile, suitable for applications that require the metafile to be of minimum size and suitable for transmission with character-oriented transmission services. SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO/IEC 8632. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO/IEC 8632 are encouraged to investi- gate the possibility of applying the most recent editions of the standards listed below. Members of IEC and IS0 maintain registers of currently valid International Standards. ISOLIEC 646: 199 1, Information technology - IS0 7-bit coded character set for information interchange. IS0 2022: 1986, Information processing - IS0 7-bit and S-bit coded character sets - Code extension techniques. IS0 2375: 1985, Data processing - Procedure for registration of escape sequences. IS0 6429: 1988, Information processing - Control functions for 7-bit and &bit coded character sets. ECMA 96, Graphics Data Syntax for a multiple Workstation Integace. CEPT, Revision of T/CD 6.1 Videotex Presentation Layer Data Syntax. SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 3 Notational conventions 3.1 7,Bit and &Bit code tables The bits of the bit combinations of the 7-bit code are identified by b7, b6, b5, b4, b3, b2, and bl, where b7 is the highest-order, or most-significant, bit and bl is the lowest-order, or least-significant, bit. The bit combinations may be interpreted to represent integers in the range 0 to 127 in binary notation by attributing the following weights to the individual bits: . Bit . Weight b7 b6 b5 b4 b3 b2 bl . . . 64 32 16 8 4 2 1 In this part of ISO/IEC 8632, the bit combinations are identified by notation of the form x/y, where x is a number in the range 0 to 7 and y is a number in the range 0 to 15. The correspondence between the nota- tions of the form xl/y and the bit combinations consisting of the bits b7 to bl is as follows: - x is the number represented by b7, b6, and b5 where these bits are given the weights 4, 2, and 1 respectively; - y is the number represented by b4, b3, b2, and bl where these bits are given the weights 8,4,2, and 1 respectively. The notations of the form x/y are the same as those used to identify code table positions, where x is the column number and y is the row number. A 7-bit code table consists of 128 positions arranged in eight columns and sixteen rows. The columns are numbered 0 to 7 and the rows are numbered 0 to 15. Figure 1 shows a 7-bit code table. An example illustrates the 7-bit code: “l/l 1” refers to the bit combination in column 1, row 11 of the code table, binary 0011011. The bits of the bit combinations of the 8-bit code are identified by b8, b7, b6, b5, b4, b3, b2, and bl, where b8 is the highest-order, or most-significant, bit and bl is the lowest-order, or least-significant, bit. The bit combinations may be interpreted to represent integers in the range 0 to 255 in binary notation by attributing the following weights to the individual bits: . Bit . Weight b8 b7 b6 b5 b4 b3 b2 bl . . . 128 64 32 16 8 4 2 1 Using these weights, the bit combinations of the 8-bit code are interpreted to represent numbers in the range 0 to 255. In this part of ISO/IEC 8632, the bit combinations are identified by notation of the form xxIyy, where XX and yy are numbers in the range 00 to 15. The correspondence between the notations of the form xx/yy and the bit combinations consisting of the bits b8 to bl is as follows: - xx is the number represented by b8, b7, b6, and b5 where these bits are given the weights 8,4, 2, and 1 respectively; - yy is the number represented by b4, b3, b2, and bl where these bits are given the weights 8,4, 2, and 1 respectively. The notations of the form ;“IxIyy are the same as those used to identify code table positions, where XX is the column number and yy is the row number. An 8-bit code table consists of 256 positions arranged in sixteen columns and sixteen rows. The columns and rows are numbered 00 to 15. Figure 2 shows an 8-bit code 3 SIST EN 28632-2:1997

ISOlIEC 8632-2: 1992 (E) 7-Bit and &Bit code tables Notational conventions table. An example illustrates the 8-bit code: 04/01 represents the 8-bit byte 01000001, whereas 4/l represents the 7-bit byte 1000001. 3.2 Code extension techniques vocabulary In describing the characters that may occur within string parameters, certain terms imported from other standards (e.g., IS0 2022) are useful. In the context of the CGM, these terms, and the concepts to which they refer, apply only within the string parameters of the TEXT, APPEND TEXT, and RESTRICTED TEXT metafile elements. 3.2.1 CO sets A CO set is a set of 30 control characters represented in a 7-bit code by O/O to l/15, except O/14 and O/l5 which shall be unused, and in an 8-bit code by OO/OO to 01/15, except 00/14 and 00/15 which shall be unused. CO sets occupy columns 0 and 1 of a 7-bit code table or columns 00 and 01 of an 8-bit code table. The meanings of CO controls within string parameters are described in 6.9.3. 3.2.2 Cl sets A Cl set is a set of up to 32 control characters represented by bit combinations OS/O0 to 09/15 in an 8-bit code. Cl sets occupy columns 08 and 09 of the 8-bit code table. In a 7-bit code the Cl control functions are represented by 2-byte escape sequences. This CGM encoding reserves the bit combinations 9/8 and 9/12 (ESC 5/8 and ESC 5/12 in a 7-bit environment, ESC = l/l 1); these shall not be part of the content of string parameters. Other Cl control characters from other standards, such as IS0 6429, may be used within string parameters by agreement between the interchanging parties. 3.2.3 G-sets The G-sets (GO, Gl, G2, G3) are coded character sets of 94 or 96 characters. CHARACTER SET INDEX designates which character set is to be the GO set. ALTERNATE CHARACTER SET INDEX designates a character set to be used as both the Gl and G2 sets. The G-sets may be “invoked into” (caused to occupy) columns 2 through 7 of a 7-bit code table, or columns 02 through 07 and 10 through 15 of an 8-bit code table. This encoding of the CGM uses the GO and Gl/G2 sets within string parameters. The G3 set may be used within the string parameters of conforming metafiles; this requires selection of the extended 7-bit or extended 8-bit mode in the CHARAmR CODING ANNOUNCER. The CGM does not provide an ele- ment to explicitly designate the G3 sets; this may be done within a text string in accordance with IS0 2022, or by other means agreed upon by the interchanging parties. SIST EN 28632-2:1997

Notational conventions ISO/IEC 8632-2: 1992 (E) Code extension techniques vocabulary A G-SET OF 94 OR 96 BIT COMBINATIONS Figure l- The 7-bit code table SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Code extension techniques vocabulary Notational conventions 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 00 01 02 03 04 05 06 07 08 09 co SET 02/q "GL" SET OF 94 OR 96 BIT COMBINATIONS IO?. 15 Cl SET "GR" SET C 94 OR 96 BIT COMBINAT ONS I15/ 15 Figure 2 - The S-bit code table SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 4 Entering and leaving the metafile environment 4.1 Implicitly entering the metafile environment The CGM coding environment may be entered implicitly, by agreement between the interchanging parties. This is suitable only if there is not to be any interchange with services using other coding techniques. 4.2 Designating and invoking the CGM coding environment from IS0 2022 For interchange with services using the code extension techniques of IS0 2022, the CGM coding environ- ment shall be designated and invoked from IS0 2022 environment by the following escape sequence: ESC 215 F where ESC is the bit combination l/l 1, and F refers to a bit combination that will be assigned by the IS0 Registration Authority for IS0 2375. The first bit combination occuring after this escape sequence will then represent the opcode of a CGM metafile element. After the end of one or more metafiles (i.e., after the END METAFILE clement) or between pictures (i.e., after the END PICTURE element), the following escape sequence may be used to return to the IS0 2022 coding environment: ESC 215 4/O This not only returns to the IS0 2022 coding environment, but also restores the designation and invocation of coded character sets to the state that existed prior to entering the CGM coding environment with the ESC 2/5 F sequence. (The terms “designation” and “invocation” arc defined in IS0 2022.) SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 5 Method of encoding opcodes Each metafile element is composed of one opcode and parameters as required. The opcodcs are coded as a sequence of bit combinations from columns 2 and 3 of the code chart. The encoding technique supplies: - the basic opcode set; - extension opcode sets. 5.1 Encoding technique of the basic opcode set The basic opcode set consists of single-byte and double-byte opcodes. Single-byte opcodes are from column 2 of the code chart. Bits b4 to bl are used to encode the opcode. The format is as follows: b8 bl +-+-- -- -+- -- -- --+ 1x10 1 Olb b b bl +-+-----+-------+ The “X” bit (bit b8) is the parity bit (or omitted bit) in a 7-bit environment. In an 8-bit environment it is 0. For double-byte opcodes the first byte is from column 3 and the second byte is from column 2 or 3 of the code chart. Bits b4 to bl of the first byte and bits b5 to bl of the second byte are used to encode the opcode: b8 bl b8 bl +-+-----+-------+ +-+---+---------+ 1x10 1 lib b b bj 1x10 lib b b b bl +-+-----+------+ +-+---+---------+ The bit combination 3/15, the EXTEND OPCODE SPACE (EOS) allows extension of the basic opcode space (see 5.2). The basic opcode set, supplied by this encoding technique consists of 496 opcodes, being: - 16 single-byte opcodes (from column 2); - 15 x 32 = 480 double-byte opcodes (first byte from column 3 except bit combination 3/15, second byte from column 2 or 3). 5.2 Extension mechanism The basic opcode set can be extended with an unlimited number of extension opcode sets by means of the EXTEND OPCODE SPACE code (EOS, 3/15). The N-th extension opcode set consists of opcodes of the basic opcode set, prefixed with n times the code EOS. The three possible formats of an opcode from the N-th extension opcode set are Opcode format Extension codes Basic opcode set codes 1 . <2/x> n times SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Method of encoding opcodes Extension mechanism n times . I ------- I I n times <3/y> <2lz> <3/y> <3/z> = 3115 X = 0,1,.,15 Y = 0,1,.,14 Z = 0,1,.,15 n = OJ,. n = 0 selects the basic opcode set. n = 1 selects the first extension opcode set. n = N selects the N-th extension opcode set. The number of opcodes supplied by this encoding technique (basic opcode set plus extension opcode sets) is 496*(n+l), where n is the number of extension sets. (Each extension set has 496 opcodes - 16 single- byte opcodes plus 480 double-byte codes.) 5.3 Opcode assignments Table 1 lists the opcode assignments for the CGM elements. All opcodes are from the basic opcode set. They are organized as follows: single-byte opcodes are assigned to Graphical Primitive elements except for some of the Circular and Elliptical output elements, where double-byte opcodes with combination 314 for the first byte are assigned. All other metafile elements have double-byte opcodes with the following bit combinations for the first byte: 310 for Delimiter Elements 311 for Metafile Descriptor Elements 312 for Picture Descriptor Elements 313 for Control Elements 315 and 316 for Attribute Elements 3/7 for Escape and External Elements 318 for Segment Control Elements and Segment Attribute Elements 9 SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Opcode assignments Method of encoding opcodes Table 1 - Opcodes for metafile elements Opcode 7-Bit coding S-Bit coding BEGIN METAFILE opcode END METAFILE opcode BEGIN PICTURE opcode BEGIN PICTURE BODY opcode END PICTURE opcode BEGIN SEGMENT opcode END SEGMENT opcode BEGIN FIGURE opcode END FIGURE opcode BEGIN PROTECTION REGION opcode END PROTECTION REGION opcode BEGIN COMPOUND LINE opcode END COMPOUND LINE opcode BEGIN COMPOUND TEXT PATH opcode END COMPOUND TEXT PATH opcode BEGIN TILE ARRAY opcode END TILE ARRAY opcode 3/O 2/O 03/o 02/o 3/O 211 03/o 02/l 3/O 212 03/o 0212 3/O 213 03/O 0213 3/o 214 03/O 0214 310 215 03/o 0215 3/o 216 03/O 0216 3/o 217 03/O 0217 310 218 03/o 02/s 310 2112 03/O 02112 3/o 2113 03/O 02113 310 2114 03/O 02114 310 2115 03/O 02115 310 310 03/O 03/o 310 311 03/O 0311 3/o 312 03/O 03/2 3/O 313 03/o 0313 METAFILE VERSION opcode 3/l 2/o 03/l 02/o METAFILE DESCRIPTION opcode 311 211 03/l 02/l VDC TYPE opcode 311 212 03/l 0212 INTEGER PRECISION opcode 311 213 03/l 0213 REAL PRECISION opcode 311 214 03/l 0214 INDEX PRECISION opcode 311 215 0311 0215 COLOUR PRECISION opcode 311 216 03/l 0216 COLOUR INDEX PRECISION opcode 311 217 03/l 0217 MAXIMUM COLOUR INDEX opcode 311 218 03/l 0218 COLOUR VALUE EXTENT opcode 311 219 03/l 0219 METAFILE ELEMENT LIST opcode 311 2110 03/l 02110 BEGIN METAFILE DEFAULTS REPLACEMENT opcode 311 2111 0311 02/H END METAFILE DEFAULTS REPLACEMENT opcode 311 2112 03/l 02112 FONT LIST opcode 311 2113 0311 02113 CHARACTER SET LIST opcode 311 2114 03/l 02114 CHARACTER CODING ANNOUNCER opcode 311 2115 0311 02115 NAME PRECISION opcode 311 310 03/l 03/o MAXIMUM VDC EXTENT opcode 311 311 0311 03/l SEGMENT PRIORITY EXTENT opcode 311 312 03/l 0312 COLOUR MODEL opcode 3/l 313 03/l 0313 COLOUR CALIBRATION opcode 311 314 03/l 0314 FONT PROPERTIES opcode 311 315 03/l 0315 GLYPH MAPPING opcode 311 316 03/l 0316 SYMBOL LIBRARY LIST opcode 311 317 0311 0317 10 SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Method of encoding opcodes Table 1 - Opcodes for metafile elements (continued) Opcode assignments Opcode 7-Bit coding S-Bit coding SCALING MODE opcode 312 2/o 0312 0210 COLOUR SELECTION MODE opcode 312 211 0312 02/l LINE WIDTH SPECIFICATION MODE opcode 312 212 0312 0212 MARKER SIZE SPECIFICATION MODE opcode 312 213 0312 0213 EDGE WIDTH SPECIFICATION MODE opcode 312 214 0312 0214 VDC EXTENT opcode 312 215 0312 0215 BACKGROUND COLOUR opcode 312 W3 0312 0216 DEVICE VIEWPORT opcode 312 217 0312 02/7 DEVICE VIEWPORT SPECIFICATION MODE opcode 312 218 0312 0218 DEVICE VIEWPORT MAPPING opcode 312 219 0312 0219 LINE REPRESENTATION opcode 312 2110 0312 02110 MARKER REPRESENTATION opcode 312 2111 0312 02/l 1 TEXT REPRESENTATION opcode 312 2112 0312 02112 FILL REPRESENTATION opcode 312 2113 0312 02113 EDGE REPRESENTATION opcode 312 2114 0312 02114 INTERIOR STYLE SPECIFICATION MODE opcode 312 2115 0312 02115 LINE AND EDGE TYPE DEFINITION opcode 312 3/O 0312 0310 HATCH STYLE DEFINITION opcode 312 311 0312 03/l GEOMETRIC PATTERN DEFINITION opcode 312 312 0312 0312 VDC INTEGER PRECISION opcode VDC REAL PRECISION opcode AUXILIARY COLOUR opcode TRANSPARENCY opcode CLIP RECTANGLE opcode CLIP INDICATOR opcode LINE CLIPPING MODE opcode MARKER CLIPPING MODE opcode EDGE CLIPPING MODE opcode NEW REGION opcode SAVE PRIMITlVE CONTEXT opcode RESTORE PRIMITIVE CONTEXT opcode PROTECTION REGION INDICATOR opcode GENERALIZED TEXT PATH MODE opcode MITRE LIMIT opcode TRANSPARENT CELL COLOUR opcode 313 2/O 0313 02/o 313 211 0313 02/l 313 212 0313 0212 313 213 0313 0213 313 214 0313 0214 313 215 0313 0215 313 216 0313 0216 313 217 0313 02/7 313 218 0313 0218 313 219 0313 0219 313 2110 0313 02110 313 2/11 0313 02/l 1 313 310 0313 0310 313 311 0313 03/l 313 312 0313 0312 313 313 0313 0313 POLYLINE opcode DISJOINT POLYLINE opcode POLYMARKER opcode TEXT opcode RESTRICTED TEXT opcode APPEND TEXT opcode POLYGON opcode POLYGON SET opcode CELL ARRAY opcode GENERALIZED DRAWING PRIMITIVE opcode RECTANGLE opcode 2/O 0210 211 02/l 212 0212 213 0213 214 0214 215 0215 216 0216 217 0217 m 02/8 219 0219 2110 02110 SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Opcode assignments Method of encoding opcodes Table l- Opcodes for metafile elements (continued) 3pcode 7-Bit coding 8-Bit coding CIRCLE opcode 314 210 0314 02/O CIRCULAR ARC 3 POINT opcode 314 211 0314 02/l CIRCULAR ARC 3 POINT CLOSE opcode 314 212 0314 0212 CIRCULAR ARC CENTRE opcode 314 213 0314 0213 CIRCULAR ARC CENTRE CLOSE opcode 314 214 0314 0214 ELLIPSE opcode 314 215 0314 0215 ELLIPTICAL ARC opcode 314 216 0314 0216 ELLIPTICAL ARC CLOSE opcode 314 217 0314 0217 CIRCULAR ARC CENTRE REVERSED opcode 314 218 0314 0218 CONNECTING EDGE opcode 314 219 0314 0219 HYPERBOLIC ARC opcode 314 2110 0314 02110 PARABOLIC ARC opcode 314 2111 0314 02/l 1 NON-UNIFORM B-SPLINE opcode 314 2112 0314 02112 NON-UNIFORM RATIONAL B-SPLINE opcode 314 2113 0314 02113 POLYBEZIER opcode 314 2114 0314 02114 POLY SY MBOL opcode 314 2115 0314 02115 BITONAL TILE opcode 314 3/O 0314 0310 TILE opcode 314 311 . 0314 03/l LINE BUNDLE INDEX opcode 315 2/O 0315 02/O LINE TYPE opcode 315 211 0315 02/l LINE WIDTH 315 212 0315 0212 LINE COLOUR opcode 315 213 0315 0213 MARKER BUNDLE INDEX opcode 315 214 0315 0214 MARKER TYPE opcode 315 215 0315 0215 MARKER SIZE opcode 315 216 0315 0216 MARKER COLOUR opcode 315 217 0315 0217 TEXT BUNDLE INDEX opcode 315 3/O 0315 03/O TEXT FONT INDEX opcode 315 311 0315 03/l TEXT PRECISION opcode 315 312 0315 0312 CHARACTER EXPANSION FACTOR opcode 315 313 0315 0313 CHARACTER SPACING opcode 315 314 0315 0314 TEXT COLOUR opcode 315 315 0315 0315 CHARACTER HEIGHT opcode 315 316 0315 0316 CHARACTER ORIENTATION opcode 315 317 0315 0317 TEXT PATH opcode 315 318 0315 0318 TEXT ALIGNMENT opcode 315 319 0315 0319 CHARACTER SET INDEX opcode 315 3110 0315 03110 ALTERNATE CHARACTER SET INDEX opcode 315 3/l 1 0315 03/l 1 FILL BUNDLE INDEX opcode 316 2/O 0316 0210 INTERIOR STYLE opcode 316 211 0316 02/l FILL COLOUR opcode 316 212 0316 0212 HATCH INDEX opcode 316 213 03/6 0213 PATTERN INDEX opcode 316 214 0316 0214 EDGE BUNDLE INDEX opcode 316 215 0316 0215 EDGE TYPE opcode 316 216 0316 0216 EDGE WIDTH opcode 316 217 0316 0217 EDGE COLOUR opcode 316 218 0316 0218 EDGE VISIBILITY opcode 316 219 03/6 0219 FILL REFERENCE POINT opcode 316 2110 0316 02110 12 SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) Method of encoding opcodes Opcode assignments Table 1 - Opcodes for metafile elements (concluded) Opcode PATTERN TABLE opcode PATTERN SIZE opcode COLOUR TABLE opcode ASPECT SOURCE FLAGS opcode PICK IDENTIFIER opcode LINE CAP opcode LINE JOIN opcode LINE TYPE CONTINUATION opcode LINE TYPE INITIAL OFFSET opcode TEXT SCORE TYPE opcode RESTRICTED TEXT TYPE opcode INTERPOLATED INTERIOR opcode EDGE CAP opcode EDGE JOIN opcode EDGE TYPE CONTINUATION opcode EDGE TYPE INITIAL OFFSET opcode SYMBOL LIBRARY INDEX opcode SYMBOL COLOUR opcode SYMBOL SIZE opcode SYMBOL ORIENTATION opcode 7-Bit coding 8-Bit coding 316 2/l 1 0316 02/l 1 316 . 2112 0316 02112 316 310 0316 03/O 316 311 0316 03/l 316 312 0316 0312 315 218 0315 02/s 315 219 0315 0219 315 2110 0315 02110 315 2/l 1 0315 02111 315 2112 0315 02112 315 2113 0315 02113 315 2114 0315 02114 315 2115 0315 02115 316 2113 0316 02113 316 2114 0316 02114 316 2115 0316 02115 316 313 0316 0313 316 314 0316 0314 316 315 0316 0315 316 316 0316 0316 ESCAPE opcode DOMAIN RING opcode MESSAGE opcode APPLICATION DATA opcode 317 210 0317 02/O 317 310 0317 03/O 317 211 0317 02/l 317 212 0317 0212 COPY SEGMENT opcode 318 210 0318 02/O INHERITANCE FILTER opcode 318 211 0318 0211 CLIP INHERITANCE opcode 318 212 0318 0212 SEGMENT TRANSFORMATION opcode 318 213 0318 0213 SEGMENT HIGHLIGHTING opcode 318 214 0318 0214 SEGMENT DISPLAY PRIORITY opcode 318 215 0318 0215 SEGMENT PICK PRIORITY opcode 318 216 0318 0216 NOTE - There is no no-op element in the character encoding. However, the character substitution mechanism allows generators to achieve this effect. 13 SIST EN 28632-2:1997

ISO/IEC 8632-2: 1992 (E) 6 Method of encoding parameters The parameter part of a CGM element may contain one or more parameters, each parameter consishg of one or more bytes. All parameters are coded in columns 4 through 7. (However, the coded representation of a ‘string’ parame- ter may include bit combinations from other columns of the code table - see the description of string parameters in 6.9). The general format of a parameter byte is b8 bl +-+-+-----------+ IXlllb b b b b bl +-+-+-----------+ The “X” (bit b8) is the parity bit (or omitted bit) in a 7-bit environment. In an 8-bit environment it is 0. Bit b7 is the parameter flag. Except for ‘string’, ‘string fixed’, and ‘data record’ parameters all parameters are encoded using one or both of two formats, Basic format or Bitstream format. 6.1 Basic format Each Basic format parameter is coded as a sequence of one or more bytes, structured as follows: b8 bl +-+-+-+-+-------+ IXlllelslb b b bl first byte +-+-+-+-+-------+ . b8 bl +-+-+-+---------+ IXlllelb b b b bl last byte +-+-+-+--------+ The “X” (bit b8) is the parity bit (or omitted bit) in a 7-bit environment. In an 8-bit environment it is 0. Bit b7 is the parameter flag. “e” (b6 of each byte) is the extension flag. For single byte parameters, the extension flag is 0. In multi-byte parameters, the extension flag is 1 in all bytes except the last byte, where it is 0. Bits b5 through bl are the data bits of the parameter. “s” is the sign bit; if equal to 0 then the integer is non-negative and if equal to 1 then the integer is negative. The number zero shall always be coded as “plus zero” 4/O. The “minus zero” coding is reserved for special usage (see 6.6.3). The Basic format is used to encode a> enumerated types (E); b) colour indices (CI); C> colour components (CCO); d) indices other than colour indices (IX); e> integers (I); 14 SIST EN 28632-2:1997

Method of encoding parameters Basic format ISO/IEC 8632-2: 1992 (E) f) real numbers (R); s) non-incremental coordinates. l-0 fixed-precision 8-bit unsigned integers - octets (UIS); 0 fixed-precision 32-bit unsigned integers (U132). The most significant part of the parameter is coded in the first byte. The least significant part of the param- eter is coded in the last byte. 6.2 Bitstream format Each Bitstream format parameter is encoded as a sequence of one or more bytes, structured as follows: b8 bl +-+-+----------+ IXlllb b b b b bl first byte +-+-+----------+ . b8 bl +-+-+-----------+ IXlllb b b b b bl last byte +-+-+----------+ The “X” is the parity bit (or omitted bit) in a 7-bit environment. In an 8-bit environment it is 0. Bit b7 is the parameter flag. Bits b6 through bl are the data bits of the parameter. The Bitstream format is used to encode: a> incremental mode coordinates (see 6.6.2); b) colour direct (see 6.8); c> colour index lists (see 6.8). d) the compressed bitstream (BS) data type (see 6.15). Bitstream data are packed in consecutive databits starting from high-numbered bits to lower-numbered bits of the first byte for the most significant part of the bitstream data. The end of a Bitstream format parameter cannot be derived from the Bitstream format itself (the format is not self-delimiting). Instead, - for incremental mode coordinates, the end of the data (which identifies the end of the Bitstream for- mat parameter) is identified by the code; - for colour index lists, the number of bits needed to encode the colour index list (which identifies the end of the Bitstream format parameter) is set by the COLOUR INDEX PRECISION element, or by the local colour precision parameter (for those elements which contain such a parameter); - for colour direct data, the number of bits needed to encode the data (which identifies the end of the Bitstream format operand) is set by the COLOUR PRECISION element, or by the local colour pre- cision parameter (for those elements which contain such a parameter). - for compressed binary colour specifiers of Tile Array elements, the SOS/ST delimiters that are also used for String operands are used to delimit the Bitstream operand. 15 SIST EN 28632-2:1997

ISOIIEC 8632-2: 1992 (E) Bitstream format Method of encoding parameters 6.3 Coding integers Integers are coded as sequences of bytes in the range from 4/O to 7/15 in the Basic format. If a byte is from columns 4 or 5 of the code table, it is either the last byte in the integer’s coded representation or it is a single-byte integer. A multi-b
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