ISO/IEC 7942-1:1994

INTERNATIONAL
ISO/IEC
STANDARD
7942-1
Second edition
1994-11-01
Information technology - Computer
graphics and image processing -
Graphical Kerne1 System (GKS) -
Part 1:
Functional description
Technologies de I ’information - Infographie et traitement d ’image -
Systeme graphique GKS -
Partie 1: Descrip tion fonctionnelle
Reference nurnber
lSO/IEC 7942-1 :1994(E)
ISO/IEC 7942-1: 1994(E)
Contents
...
Vlll
Foreword .
ix
Introduction .
.................................................................................................................
1 Scope
2 Normative references .
3 Definitions .
.....................................................................................................
4 Conformance
Specification .
4.1
Registration .
4.2
........................................................................................................
5 Concepts.
Bietures .
5s
Output primitive classes and attributes .
5.2
Werkstations .
5.3
Coordinate Systems and transformations .
5.4
Logical Input devices .
5.5
Picture part store .
State lists .
5:7
Description tables .
5.8
Metafiles and archives .
5.
Routing to the backdrop .
5.
5.11 Audi% trail .
512 Segments .
..................................................... 15
5,13 Compatibility with ISO 7942: 1985
51 SUl?lIlXil-y .
.........................................................................
The Graphical Kerne1 System
Initialization .
6.1
..................................................................................
6.2 Graphical output
Output primitive classes .
62.1
Output primitive attributes .
6.2.2
............................................................
6.3 Normalkation transformations
..................................................................................
6.4 Bicture part store
Bicture gart creation .
6AJ
Picture part functions .
Adding picture parts .
Pic ture part archiving .
6.4*4
.................................................................................
65 The NDC gicture
Introduction .
6.5.1
NIX picture operations .
63.2
NDC metafiles .
................................................................................
6.6 Sektion criterion
....................................................................................
6,7 Graphical input
...........................
6.7s Introduction to logical input devices
.........................................
6.7.2 Logical input device model
................. ..2 4
6.7.3 Operating modes of logical input devices
........................... 25
6.7.4 Input queue and current event report
0 ISO/IEC 1994
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ISO/IEC Copyright Office l Case postale 56 l CH- 1211 Geneve 20 l Switzerland
Printed in Switzerland
ii
ISO/IEC 7942=1:1994(E)
OISO/IEC
..................................................................................
68 . Inquiry functions
.....................................................................................
69 Error handling
..2 6
.........
6110 Special interfaces between GKS and the application prograrn
.............................................................................................
6.11 Backdrap
..............................................................................
6.12 Audit and playback
........................................................................
7 Workstation dependent control
.........................................................................................
7.1 Introduction
.................................................................
Workstation characteristics
7.2
........................................................................
7.3 Selecting a workstation
7.4 Selec tion criteria .
Viewing .
75 .
...............................................................
76 Workstation transformations
.................................................................................
7:7 Output primitives
7.8 Colour .
.........................................................................
79 Setting representations
..........................................................................
7110 Removing a backdrop
................................................................................
7.11 Visual effect state
.................................................................................
7.12 Realized metafile
...........................................................................
7.13 Logical input devices
Introduction .
7.13.1
.......................... 35
Initialization of logical input devices
7.13.2
..3 5
....
Definition of logical and composite input devices
7.13.3
.....................................................
7.14 Sending messages to a workstation
.............................................................................................
8 Output primitives
Introduc tion .
8.1
.......................................................................
Curve output primitives
82 .
..........................................................
8.2.1 Curve primitives
............................................................
Curve attributes
8.2.2
.....................................................................
Marker output primitives
8.3
.........................................................................
Area output primitives
8.4
............................................................
Area primitives
8.4.1
....................................................
Definition of interior
8.4.2
..............................................................
Area attributes
8.4.3
.................................................................
Character output primitives
8.5
.................................................................
8.5.1 Introduction
......................................................
8.5.2 Glyph specification
....................................................................
8.5.3 Glyph size
...................................................................
8.5.4 Text extent
................................................................
8.5.5 Text skewing
.............................................................
8.5.6 Text alignment
............................................................
8.5.7 Text orientation
..........................................................
8.5.8 Transformed text
8.5.9 Precision .
.................................................
8.5.10 Estimate of text extent
.......................................................................
8.6 Image output primitives
......................................................................
8.7 Design output primitives
.................................................................
8.7.1 Introduction
8.7.2 S tencils .
..........................................................
8.7.3 S tencil attributes
.....................................................
8.7.4 S tencil composi tion
...................................................................
8.7.5 Tiling store
..........................................
8.7.6 Stencil and tiling functions
. . .
ISO/IEC 7942-1: 1994(E) OISO/IEC
8.8 Generalized drawing primitive . 59
9 Logical input device classes . 60
9.1 Introduction . . 60
Measures of each logical input device class . 60
9:3 Transformation of LOCATOR and STROKE input . . 61
9.3.1 Transformation of LOCATOR input . 61
.............................. 63
9.3.2 Transformation of STROKE input
9.4 Prompt and echo types .
LOCATOR prompt and echo types . 63
9.4.1
9.4.2 STROKE prompt and echo types . 64
9.4.3 VALUATOR prompt and echo types . 64
9.4.4 CHOICE prompt and echo types . 65
9.4.5 PICK prompt and echo types . 65
9.4.6 STRING prompt and echo types . 66
10 Segments and workstation activation . 67
10.1 Introduction . . 67
10.2 Selection criteria . 67
Segment state list . 68
10.3
10.4 Workstation activation . 68
10.5 Segment creation . 68
10.6 Segment manipulation . 68
10.7 Segment attributes .
10.8 Segment storage .
10.9 Clear workstation .
11 Data types . .
11.1 Data type definitions .
11.1.1 Notational conventions .
11.1.2 Basic types .
11.1.3 Data types for GKS control .
.................................. 73
11.1.4 Data types for output primitives
................................... 75
11.1.5 Data types for output attributes
Data types for transformations . 78
11.1.6
11.1.7 Data types for NDC picture . 79
11.1.8 Data types for metafiles . 79
Data types for picture parts and archives . .7 9
11.1.9
Data types for Utility functions . 80
11.1.10
............................................... 80
11.1.11 Data types for Segments
..................................................... 81
11.1.12 Data types for input
.............................. 82
11.1.13 Data types for workstation control
11.1.14 Data types for inquiry functions .
11.1.15 Data types for operating state .
.84
11.1.16 Data types for font and glyph functions .
11.1.17 Data types for audit trails .
11.1.18 Data types for selection criteria .
11.1.19 Data types for paths, tilings and stencils . .85
11.2 Data type definitions for state lists and description tables. . .87
11.2.1 Introduction . 87
11.2.2 Operating state list (OSL) .
11.2.3 GKS description table (GDT) . 87
11.2.4 GKS state list (GSL) . 87
11.2.5 Workstation state list (WSL) . 88
11.2.6 Workstation description table (WDT) . .88
iv
OISO/IEC ISOIIEC 7942=1:1994(E)
11.2.7 Error state list (ESL) . 90
11.2.8 Segment state list (SSL) . 90
11.2.9 Stencil state list (STSL) . 90
11.3 Initial values of state lists and description tables . 90
11.3.1 Operating state list . 90
11.3.2 GKS description table . 90
11.3.3 GKS state list . 90
11.3.4 Workstation state list . 92
........................ .92
11.3.5 Generic workstation description table
Error state list . 92
11.3.6
11.3.7 92
Segment state list .
11.3.8 Stencil state list .
12 Workstation independent functions .
12.1 Conti-01 functions . 93
12.2 Output functions . 94
12.3 Design output functions . 95
12.4 Output attributes . 97
12.5 Normalization transformation functions . 98
12.6 NDC picture functions . 99
12.7 Metafile functions .
12.8 Picture part store functions .
12.9 Input functions .
................................................................... 104
12.10 Font and glyph functions
............................................................ 104
12.11 Audit and playback functions
12.12 Inquiry functions . 105
................................................................................. 107
12.13 Utility functions
Utility functions for output primitives . 107
12.14
................................................................................... 109
13 Workstation functions
............................................................................... 109
13.1 Conti-01 functions
13.2 Inquiry functions . 112
............................................................................. 114
13.3 Retrieval functions
13.4 Viewing utility functions . 115
13.5 Colour Utility functions . 115
14 Segment and workstation activation functions . 116
14.1 Segment functions .
14.2 Workstation activation functions .
14.3 Utility func tions . 119
Annexes
............................................................................. 120
A Function and data type list
Functions alphabetic . 120
A.1
A.2 Functions Order of appearance . 122
......................................................................... 126
A.3 Data types alphabetic
........................................................................................................ 128
B Error list
.............................................................................. 128
B.1 Function error list
Error list ordered by error number . 138
B.2
Language binding considerations . 140
C
................................................................................... 146
D Allowable differentes
General . . 146
D.1
............................................................................. 146
D.2 Global differentes
................................................... 146
D.3 Workstation dependent differentes
............ ................................................................................... 149
E Colour models
................................................................................................. 150
F Bibliography
V
OISO/IEC
ISO/IEC 7942-1: 1994(E)
....................................... 151
G An approach to compatibility with ISO 7942: 1985
G.1 Introduction .
G.2 Format .
G.2.1 Compatibility aspects .
G.2.2 Language binding .
....................................... 151
G.2.3 Notation used in this annex
................................................................................... 151
G.3 Data structures
Introduction .
G.3.1
............................................ 152
G.3.2 Compatibility data types
G.3.3 Compatibility operating state list (COSL) .152
................
list (CGSL) .152
G.3.4 Compatibility GKS state .
.152
G.3.5 Compatibility workstation state list (CWSL) .
.153
G.3.6 Compatibility Segment state list (CSSL) .
............................................................................... 153
G.4 Control functions
OPEN GKS . 153
G.4.1
G.4.2 OPEN WORKSTATION .
G.4.3 CLOSE WORKSTATION .
ACTIVATE WORKSTATION . 154
G.4.4
DEACTIVATE WORKSTATION . 155
G.4.5
G.4.6 CLEAR WORKSTATION .
G.4.7 Deferral states . 155
G.5 Output and attribute functions .
G.6 Transformation functions . 156
G.6.1 SET VIEWPORT . 156
G.6.2 SET WINDOW .
G.6.3 SELECT NORMALIZATION
TRANSFORMATION .
............................................... 157
G.7 Workstation transformation functions
G.8 Segment functions .
............................................................... 157
G.8.1 Introduction
CREATE SEGMENT . 157
G.8.2
DELETE SEGMENT FROM WORKSTATION.15 7
G.8.3
ASSOCIATE SEGMENT WITH WORKSTATION158
G.8.4
SEGMENT TO WORKSTATION .158
G.8.5 COPY .
G.8.6 INSERT SEGMENT .
G.8.7 Segment attributes .
G.9 Input functions .
G.9.1 Introduction .
G.9.2 Simultaneous events .
Pick input 160
G.9.3 .
............................................................................................... 160
G.10 GKSM
G.lO.1 READ ITEM FROM GKSM . 160
G.lO.2 GET ITEM FROM GKSM . 160
INTERPRET ITEM 160
G.lO.3 .
WRITE ITFM TO GKSM . 161
G.lO.4
G.11 Inquiry functions . 161
G.ll.1 functions for operating state value .16 1
Inquiry .
.161
G.ll.2 Inquiry functions for GKS description table .
........................... 161
G.ll.3 Inquiry functions for GKS state list
.161
G.ll.4 Inquiry functions for workstation state list .
G.ll.5 Inquiry functions for workstation
description table .
vi
OISO/IEC ISO/IEC 794201:1994(E)
G.11.6 Inquiry functions for Segment state list . 162
G.11.7 Pixel inquiries . 162
G.11.8 Inquiry functions for GKS error state list . .162
G.12 Utility functions . 162
G.13 Error handling . 162
G.13.1 Matthing error numbers . 162
G.13.2 Using the Utility function .
G.14 Conclusions . 163
H Compatibility with the Computer Graphits Reference Model
ISO/IEC 11072: 1992 (informative) .
H.l Introduction .
H.2 Environments . 164
H.3 Fan-out and fan-in . 164
H.4 Extemal interfaces . 164
HS Processing elements .
H.6 Compositions . .
H.7 Collec tions .
H.8 Clipping .
vii
ISOAEC 7942-1: 1994(E) OISO/IEC
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical Commis-
sion) 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 established by the
respective organization to deal with particular fields of technical activity. ISO and IEC technical committees
Other international organizations, govemmental and non-
collaborate in fields of mutual interest.
govemmental, in liaison with ISO and IEC, also take part in the work.
In the field of information technology, ISO and IEC have established a joint technical committee, ISO/IEC
JTCl. Draft International Standards adopted by the joint technical committee are circulated to national bodies
for voting. Publication as International Standard requires approval by at least 75% of the national bodies cast-
ing a vote.
International Standard ISO/IEC 7942-1 was prepared by Joint Technical Committee ISO/IEC JTCl, Informa-
tion technology, Sub-Committee 24, Computer graphics and image processing.
This second edition cancels and replaces the first edition (ISO 7942: 1985), which has been technically revised.
ISO/IEC 7942 consists of the following Parts, under the general title Information technology - Computer
graphics and image processing - Graphical Kerne1 System (GKS):
Part 1: Functional description
Part 2: NDC metajle
Part 3: Audit trail
Part 4: Picture part archive
Annexes A and B form an integral part of this part of ISO/lEC 7942. Annexes C, D, E, F, G, and H are for
information only.
. . .
Vlll
OISO/IEC ISO/IEC 794201:1994(E)
Introduction
The Graphical Kerne1 System (GKS) provides a set of functions for Computer graphics programming that tan
be used by a range of applications. The main motivations for standardization are to improve portability of pro-
grams and to define a basic methodology. Portability is achieved by providing all the capabilities necessary in
a device independent way. The following principles are used in specifying GKS:
a) Design: the three goals are consistency of approach, compatibility with related Standards and orthogonal
functionality where possible.
b) Functionality: the goals are completeness with the minimal set of functions. Organization of functions
should be such as to achieve compact programs. Richness should be provided by Utilities and toolkits on
top of GKS rather than non-Standard extensions to GKS.
c) Clarity: the underlying concepts should be easily understood, especially by the application programmer.
To achieve this, GKS is defined using a small set of functions with precise specification of the data struc-
tures that define the state of GKS and the effect that functions have on this state.
d) Error handling: all errors caused by incorrect function invocations or intemal failures are logged with
the application having control over the action taken.
e) Separation of device dependent functionality: in GKS there is a clear Separation between the functional-
ity that is device dependent and device independent. GKS has the concept of a workstation which deals
with all device dependent functions.
f) Implementation: GKS should be realizable in a wide range of host languages. The support GKS requires
GKS should be efficient to implement on commonly
from the operating System should not be excessive.
available hardware and it should be easy to produce a robust product.
This International Standard (known informally as “GKS-94 ”) has a strong relationship to the principles and
functionality of ISO 7942:1985 (known informally as “GKS-85 ”). However, it has been updated to provide
additional functionality, cleaner concepts and an International Standard for modern hardware. Minor changes
made include some additional primitives, some minor extensions to input, a clearer definition of the NDC pic-
ture and simplification of deferral.
A nameset attribute has been added and this is used as a selection criterion for a range of functions. As a
result, the equivalent of the ISO 7942: 1985 Segment (picture Part) no longer needs attributes separate from the
primitive attributes. The Segment facilities of ISO 7942:1985 are provided in terms of the new picture part
store.
The ISO 7942:1985 metafile is replaced by an audit trail and an NDC metafile based on the Computer Graph-
ics Metafile (ISO/IEC 8632).
ix
ISO/IEC 7942=1:1994(E) OISO/IEC
Introduction
X
INTERNATIONAL STANDARD OISO/IEC ISO/IEC 7942=1:1994(E)
Information technology - Computer graphics and image processing -
Graphical Kerne1 System (GKS) - Part 1: Functional description
1 Scope
This part of ISO/IEC 7942 specifies a set of functions for Computer graphics programming, the Graphical Ker-
ne1 System (GKS). It provides functions for two dimensional graphical output, the storage and dynamic
modification of pictures, and Operator input. GKS functions and datatypes are specified independently of pro-
gramming languages.
GKS establishes a System for device independent graphics programming by separating picture composition
and interaction from the realization of the pictures on a specific output device and the input devices used by the
Operator.
This International Standard is applicable to a wide range of applications that produce two dimensional pictures
on vector or raster graphical devices in monochrome or colour. Operator interaction is allowed with these pic-
tures.
OISO/IEC
ISO/IEC 7942-1: 1994(E)
2 Normative references
The following Standards contain provisions which, through reference in this text, constitute provisions of this
patt of ISO/IEC 7942. At the time of publication, the editions indicated were valid. All Standards are subject
to revision, and Parties to agreements based on this patt of ISO/IEC 7942 are encouraged to investigate the
possibilities of applying the most recent editions of the Standards 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 g-bit coded Character sets - Code extension tech-
niques.
ISO 2382-13: 1984, Data processing - Vocabulary - Part 13: Computer graphics.
ISO 6093: 1985, Information processing - Representation of numerical values in Character strings for informa-
tion interchange.
ISO/IEC 8632: 1992, Information technology - Computer graphics - Metajle for transfer and storage of picture
description information
- Part 1 : Functional specijcation.
- Part 2 : Character encoding.
- Part 3 : Binary encoding.
- Part 4 : Clear text encoding.
ISO/IEC 9541: 1991, Information technology - Font information interchange.

OISO/IEC ISO/IEC 7942=1:1994(E)
3 Definitions
For the purposes of this part of ISO/IEC 7942, the following definitions apply.
3.1 picture: A spatially structured sequence of output primitives destined for stora or display on a worksta-
lowing pictures exist: NDC picture, logical picture, realized pi
tion. The fol .cture.
3.1.1 NDC picture: The picture in which graph ical output is composed by the application and
program
with which the Operator interacts using graphical input devices.
the NDC picture for a particular workstation in which
3.1.2 logical picture: The picture constructed from
logical attributes are bound to output primitives.
3.1.3 realized picture: The picture constructed from the logical picture for a particular workstation by
binding the precise definition of colours specified either directly or indirectly. The realized picture is
displayed on the workstation ’s display space.
3.2 workstation: A display space and associated input peripherals.
3.2.1 display surface: The physical area on a display device onto which display spaces are mapped.
3.2.2 display space: The area available for displaying images on a particular workstation.
3.3 coordinate System: The metric used to specify graphical output and positional input. The coordinate sys-
tems are world coordinates, normalized device coordinates, logical device coordinates and device coordinates.
All coordinate Systems are cartesian.
3.3.1 world coordinates (WC): The coordinates used by the application program to define output primi-
tives and positional input.
3.3.2 normalized device coordinates (NDC): The coordinates used to define the NDC picture and picture
parts.
3.3.3 logical device coordinates (LDC): The coordinates used to define the logical picture.
3.3.4 device coordinates (DC): The coordinates used to define realized pictures on a workstation.
3.4 transformation: A process for transforming one coordinate System to another.
3.4.1 normalization transformation: A window-to-viewport transformation that maps positions in WC to
NDC.
3.4.2 normalization transformation number: An identifier of a particular normalization transformation.
transforms the NDC coordinate system to one more
3.4.3 view orientation: A transformation that
appropriate for the Object to be viewed.
3.4.4 view mapping: A transformation applied after view orientation to map to LDC coordinates.
3.4.5 workstation transformation: A workstation window-to-viewport mapping that maps positions in
LDC to device coordinates, preserving aspect ratio.
3.5 scissoring: Restricting the appearance of an output primitive on a display by either clipping or shielding.
3.51 view scissoring: Scissoring applied to output primitives in a view after view orientation and view
mapping. View scissoring may be postponed until after the workstation transformation.
3.6 picture part store: A collection of picture Parts.
3.6.1 picture Part: A sequence of output primitives with associated attributes.
3.7 state 1%: A data structure whose entries specify the current values of variables relating to GKS as a whole
(GKS state list) or to a specific workstation (workstation state list).
3.8 description table: A data structure whose entries specify the capabilities of an implementation (GKS
description table) or a type of workstation (generic workstation description table) or an instance of a type of
workstation (workstation description table).
@ISO/IEC
ISO/IEC 7942-1: 1994(E)
Definitions
3.9 backdrop: Graphical output that appears on the workstation but is not part of the NDC picture, logical pic-
ture, or reahzed picture. The backdrop arrives at the display device on a separate channel from the realized
picture. It is device dependent how the two appear relative to each other.
3.9.1 router: A switch which controls the destination to which output primitives are dispatched.
3.10 output primitive: A basic graphical element used to construct the NDC picture and picture parts.
represen ti flow of information across the interface
3.11 audit trail: The extemal entity for ng the sequential
between the application and GKS.
3.12 output primitive classes: A classification associated with output primitives. A set of logical attributes
apply to all output primitive types in a class. The output primitive classes are curve, marker, area, Character,
image, design. The output primitive, generalized drawing primitive, does not belong to any class.
3.12.1 curve: A class of output primitive which generates a set of curves. The output primitives in the
class are set of polyline, set of nurb and set of conic section.
which
of output primitive consisting of a set of polylines each of con-
3.12.1.1 set of polyline: A type
sists of a connected sequence of straight lines between specified Points.
3.12.1.2 set of nurb: A type of output primitive consisting of a set of curves each of which is defined
by a nurb.
Both rational and non-rational ver-
3.12.1.2.1 nurb: A curve defined by a non-uniform B-spline.
sions are allowed.
3.12.1.3 set of conic section :Atypeof output primitive consisting of a set of curves each of which
defined by a conic section.
3.12.2 marker: A class of output primitive which generates a set of Symbols. The only output primitive in
the class is polymarker.
3.12.2.1 polymarker: A type of output primitive consisting of a set of positions at which Symbols arc
placed.
3.12.3 area: A class of output primitive which generates a set of areas with edges. The output primitives in
the class are set of fill area, set of closed nurb, set of elliptic sector, set of elliptic Segment and set of elliptic
disc.
3.12.3.1 set of fill area: A type of
output primitive consisting of a set of areas each of which is defined
sequence of connected
by a closed Points.
3.12.3.2 set of closed nurb: A type of output primitive consisting of a set of each of which is
defined by a closed nurb.
3.12.3.2.1 closed nurb: A nurb which has the first Point connected to the end point to produce a
closed curve if the two points are not coincident.
3.12.3.3 set of elliptic sector: A type of output primitive consisting of a set of areas each of which is
defined by an elliptic arc. Esch elliptic arc area is closed by lines from the ends of the arc to the centre
of the ellipse.
3.12.3.4 set of elliptic Segment: A type of output primitive consisting of a set of areas each of which is
defined by an elliptic arc. Esch elliptic arc area 1s closed by joining the ends of the arc
3.12.3.5 set of elliptic disc: A type of output primitive consisting of a set of each of which is
defined by a complete ellipse.
3.12.3.6 edge: The boundaries of closed regions defined in the area class of output primitives.
3.12.4 Character: A class of output primitive which generates a sequence of ,s. The only output prim-
gl YPh
itive in the class is text.
3.12.4.1 text: A type of output primitive consisting of a sequence of glyphs defined relative to a posi-
tion.
ISO/IEC 794291:1994(E)
OISO/IEC
Definitions
3.12.4.1.1 giyph: A recognizable abstract graphic Symbol which is independent of any specific
design (ISO/IEC 954 1).
3.12.4.1.2 glyph body: A rectangle used by a font designer to define a glyph shape (see figure 1).
All glyph bodies in a font have the same height.
3.12.4.1.3 glyph shape: The set of information in a glyph representation used for displaying the
dimensions and positioning of the glyph shape (ISO/IEC 9541).
The glyph shape and glyph metrics associated with a specified
3.12.4.1.4 glyph representation:
glyph in a font resource (ISO/IEC 9541).
3.12.4.1.5 topline: A horizontal line at the top of a glyph body (see figure 1) which is just above the
upper limit of all glyph shapes in a font. Ascenders and accents are below the topline.
3.12.4.1.6 capline: A horizontal line within a glyph body (see figure 1) which, for many glyph
definitions, has the appearance of being the upper limit of the glyph shape. An ascender may pass
above this line and in some languages an additional mark (for example an accent) over the glyph
may be defined above this line. All caplines in a font are in the same Position in the glyph bodies.
3.12.4.1.7 baseline: A horizontal line within a glyph body (see figure 1) which, for many glyph
A descender Passes below
definitions, has the appearance of being a lower limit of the glyph shape.
this line. All baselines in a font are in the same Position in the glyph bodies.
3.12.4.1.8 halfline: A horizontal line between the capline and the baseline within the glyph body
(see figure l), about which a horizontal string of glyphs in a font would appear centrally placed in
the vertical direction. All halflines in a font are in the same Position in the glyph bodies.
3.12.4.1.9 bottomline: A horizontal line at the bottom of the glyph body (see figure 1) which is just
below all descenders in a font. All bottomlines in a font are in the same Position in the glyph
bodies.
3.12.4.1.10 centreline: A vertical line bisecting the glyph body (see figure 1).
3.12.4.1.11 leftline: A vertical line at the left of a glyph body (see figure 1) which is to the left of
all glyph shapes in a font.
3.12.4.1.12 rightline: A vertical line at the right of a glyph body (see figure 1) which is to the right
of all glyph shapes in a font.
----
top
---
cap
- glyph body
half - - -
base ---
I
bottom - - - -
I I
I
I I I
left centre right
Figure 1 - Glyph coordinate System
3.12.4.1.13 font: A collection of glyph images having the same basic design (ISO/IEC 9541).
3.12.4.1.14 font resource: A collection of glyph representations together with description and font
metric information which are relevant to the collection of glyph representations as a whole
ISO/IEC 7942-1: 1994(E) OISO/IEC
Definitions
(ISO/IEC 954 1).
3.12.4.1.15 posture: The extent to which the shape of a glyph or set of glyphs appear to incline,
including any consequent design or form Change (ISO/IEC 9541).
3.12.4.1.16 escapement Movement of the current position on the presentation surface after a glyph
representation is imaged (ISO/IEC 954 1).
3.12.5 image: A class of output primitive which generates images. The only output primitive in the class is
cell array.
3.12.5.1 cell array: A type of output primitive defined by a rectangular grid of equal size rectangular
cells, each having a Single colour.
3.12.6 design: A class of output primitive which generates graphical output by extruding a tiling through a
stencil. Stencils are stored in the stencil store. Tilings
...