ISO/IEC 9541-3:1994/Amd 2:2009

INTERNATIONAL ISO/IEC
STANDARD 9541-3
First edition
1994-05-01
AMENDMENT 2
2009-04-01

Information technology — Font
information interchange —
Part 3:
Glyph shape representation
AMENDMENT 2: Additional shape
representation technology for Open Font
Format
Technologies de l'information — Échange d'informations sur les
fontes —
Partie 3: Représentation de la forme de glyphes
AMENDEMENT 2: Technologie de représentation de forme
additionnelle pour format de fontes ouvert




Reference number
ISO/IEC 9541-3:1994/Amd.2:2009(E)
©
ISO/IEC 2009

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ISO/IEC 9541-3:1994/Amd.2:2009(E)
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ISO/IEC 9541-3:1994/Amd.2:2009(E)
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 Standards 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 IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. 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.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
Amendment 2 to ISO/IEC 9541-3:2008 was prepared by Joint Technical Committee ISO/IEC JTC 1,
Information technology, Subcommittee SC 34, Document description and processing languages.
This Amendment appends an additional glyph shape representation technology for the harmonization of
ISO/IEC 9541-3 to Open Font Format (ISO/IEC 14496-22). In Open Font Format file, the scalable glyph shape
representations by TrueType instructions or Adobe Type2 CharStrings are possible, but ISO/IEC 14496-22
does not include it. For the harmonization between ISO/IEC 9541 and ISO/IEC 14496-22, this Amendment
covers Adobe Type2 CharStrings that is the half of the scalable glyph shape representation in
ISO/IEC 14496-22. It is an extended version of ISO/IEC 9541-3 Type 1 glyph shape representation.
The additional interchange format is described by SGML (Standard Generalized Markup Language)
conforming to ISO 8879:1986 and ISO 8879:1986/Cor.2:1999 (Annex K: Web SGML Adaptations).

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ISO/IEC 9541-3:1994/Amd.2:2009(E)

Information technology — Font information interchange —
Part 3:
Glyph shape representation
AMENDMENT 2: Additional shape representation technology for
Open Font Format
Page 3, 1.7.2
Replace the declaration with the following:





  







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ISO/IEC 9541-3:1994/Amd.2:2009(E)
Page 45
Add the following after Section 3:
Section 4: Open Type 3 glyph shape representation
4.1 Scope
This section specifies the architecture and interchange format of one standard Glyph Shape Representation:
ISO/IEC 9541 Standard OPEN TYPE 3. The Open Type 3 glyph shape representation is designed for the
harmonization to the glyph shape representation used in “CFF” table in Open Font Format
(ISO/IEC 14496-22). It is an extended version of ISO/IEC 9541-3 Type 1 glyph shape representation.
4.2 Definitions
This section uses the terms defined by 2.2. Extra terms in the following definitions are specific to this section.
4.3 Overview of Open Type 3 glyph shape representation architecture
4.3.1 Difference from Type 1 glyph shape representation
The original ISO/IEC 9541-3 Type 1 glyph shape representation used graphical drawing operators that take
single set of operands. For example, relative lineto operator (rlineto, described in 2.7.3.2.5) takes 2
number object operands of dx and dy that specifies relative displacements. To compress the glyph procedures,
the Open Type 3 glyph shape representation enhances Type 1 glyph procedure operators to take multiple set
of operands. The relative lineto operator in the Open Type 3 glyph shape representation recognizes the
operand list as an array of pairs of dx and dy. By this enhancement, the glyph procedure repeating rlineto
operator can be compressed to multiple sets of relative displacements and single rlineto operator. By the
operator to be interpreted and the length of the operand list, the glyph procedure interpreter dynamically
determines how many sets of operands are taken from the tail of operand list.
4.3.2 Extended virtual machine
The interpretation of Open Type 3 glyph procedure is modelled by the virtual machine that is described in
2.7.1. To illustrate the interpretation of Open Type 3 glyph shape representation, “a transient array” to store
any objects is introduced in state variables (described in 2.7.1.4). The Open Type 3 glyph procedure has no
operators to allocate, free, initialize the transient array explicitly, it must be allocated dynamically or
pre-allocated before the interpretation. The size of the transient array must at least 32 elements, although
individual implementations may have longer array. As other state variables, the entries of the transient array
are persistent only during the interpretation of each glyph procedures. The transient array has no default
values. Therefore, it is possible that individual implementation resets all entries to number 0, or to random
number, or keeps the objects stored in previous interpretation.
4.4 Open Type 3 glyph shape representation
By the comparison with original Type 1 glyph shape representation in the section 2, the Open Type 3 glyph
procedure is classified into 4 groups.
• Original Type 1 glyph procedure operators that are not modified from the definition in section 2
• Enhanced Type 1 glyph procedure operators that the syntaxes are enhanced for Open Type 3
• Additional operators that are not defined in original Type 1 glyph shape representation
• Obsolete operators that described in section 2 but deprecated in Open Type 3
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ISO/IEC 9541-3:1994/Amd.2:2009(E)
Some operators in the Open Type 3 glyph procedure take the multiple sets of the operands, and the number
how many sets are taken is calculated dynamically from the length of the operand list when the operator is
interpreted. For the description of such operators' syntax, following notation is used for enhanced operators.
Other notations follow to the conventions defined in 2.7.3.
Table 3 —Symbols preceding glyph procedure notation for Open Type 3 glyph shape representation
operand-list notation Meaning
{.} indicates grouping for set of operands
? takes zero or one operand or set of operands if available in the operand list.
+ takes the array of operand or set of operands as many as available from the operand list.
4.4.1 Unchanged Type 1 glyph procedure operators
The following operators are same as original Type 1 glyph procedures.
4.4.1.1 Unchanged operators for starting and finishing
4.4.1.1.1 Reference point and escapement (rpe)
This operator is same as that described in 2.7.3.1.1.
4.4.1.1.2 Horizontal reference point and escapement (xrpe)
This operator is same as that described in 2.7.3.1.2.
4.4.1.1.3 End glyph (endglyph)
This operator is same as that described in 2.7.3.1.3.
4.4.1.1.4 Standard indexed accented glyph (siag)
This operator is same as that described in 2.7.3.1.4.
4.4.1.2 Unchanged path construction operators
For the following graphical operators, the expected result by giving multiple sets of operands is identical to the
result by the final set of operands only. The detailed behaviours of the operators are described in 2.7.3.
4.4.1.2.1 Closepath (closepath)
This operator is same as that described in 2.7.3.2.1.
4.4.1.2.2 Horizontal moveto (hmoveto)
This operator is same as that described in 2.7.3.2.3.
4.4.1.2.3 Relative moveto (rmoveto)
This operator is same as that described in 2.7.3.2.6.
4.4.1.2.4 Vertical moveto (vmoveto)
This operator is same as that described in 2.7.3.2.10.
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ISO/IEC 9541-3:1994/Amd.2:2009(E)
4.4.1.2.5 Set current point (setcurrentpoint)
This operator is same as that described in 2.7.3.2.11.
4.4.1.3 Unchanged arithmetic operator
For the following arithmetic operator, giving multiple sets of operators is impossible because the result is
stacked per each set.
4.4.1.3.1 Divide (div)
This operator is same as that described in 2.7.3.4.1.
4.4.1.4 Unchanged subroutine and subroutine-related operators
The following operators switch the sequence of glyph procedure tokens.to be interpreted. Therefore it is
impossible to take multiple sets of operands.
4.4.1.4.1 Call subroutine (callsubr)
This operator is same as that described in 2.7.3.5.1.
4.4.1.4.2 Return (return)
This operator is same as that described in 2.7.3.5.2.
4.4.1.4.3 Call utility subroutine (callutilsubr)
This operator is same as that described in 2.7.3.5.3.
4.4.2 Enhanced Type 1 glyph procedure operators
The following operators are enhanced to take multiple set of operands.
4.4.2.1 Enhanced path construction operators
The following operators are designed to draw a line or curve between the current point memorized by
interpreter and the parameters given by the set of operands. The interpretation updates the current point in
the interpreter. In the description of glyph outline, they are most frequently used. Collecting all control point
and omitting similar operator can reduce the size of the procedure. In most enhancements, the operators are
enhanced to draw the zig-zag kinked line.
4.4.2.1.1 Horizontal lineto (hlineto)
The original syntax of this operator in Type 1 glyph shape representation is described in 2.7.3.2.3. This
operator in Open Type 3 glyph shape representation is interpreted by most appropriate syntax in following
syntaxes:
* dx1 dy2 . dxN hlineto (00/06) *
* dx1 dy2 . dxN dy(N+1) hlineto (00/06) *
and appends the alternating horizontal and vertical line from the current point. The first line is horizontal and
the second line is vertical (specified by only dy1).
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ISO/IEC 9541-3:1994/Amd.2:2009(E)
4.4.2.1.2 Horizontal-vertical curveto (hvcurveto)
The original syntax of this operator in Type 1 glyph shape representation is described in 2.7.3.2.4. This
operator in Open Type 3 glyph shape representation is interpreted by most appropriate syntax in following
syntaxes:
* dx1 dx2 dy2 dy3 dx3? hvcurveto (01/15) *
* dx1 dx2 dy2 dy3 {dya dxb dyb dxc dxd dxe dye dyf}+ dxf? hvcurveto (01/15) *
* {dxa dxb dxb dyc dyd dxe dye dxf}+ dyf? hvcurveto (01/15) *
and appends one or more Bézier curves to the current point. The specification of a Bézier curve from
currentpoint requires 6 operands. They are x1, y1, x2, y2, x3, y3 in figure 6, x0 and y0 are given by
currentpoint. In the first and second syntax of this operator, the tangent of beginning of first Bézier curve must
be horizontal (y1=y0), and that of ending of first Bézier curve must be vertical (x3=x2). By this restriction, the
number of operands for the first Bézier curve is reduced to 4 (dx1, dx2, dy2, dy3). The restriction of beginning
and ending tangents are alternating. The second Bézier curve must start with vertical tangent and finish with
horizontal tangent specified by 4 operands (dya, dxb, dyb, dxc), because the first Bézier curve finishes with
vertical tangent. The ending tangent of the final Bézier curve is not restricted. In basic syntax, although the
final Bézier curve is specified by 4 operands (dxd, dxe, dye, dyf in the first and second syntax, or dyd, dxe,
dye, dxf in the third syntax), extra operand (dxf in the first and second syntax, or dyf in the third syntax) makes
sloping end of final Bézier curve. The standard order of 2 operands is x and y to specify a point, but the order
of extra operand is non-standard y and x order in the first and second syntax.
4.4.2.1.3 Relative lineto (rlineto)
The original syntax of this operator in Type 1 glyph shape representation is described in 2.7.3.2.5.
* {dxa dya}+ rlineto (00/05) *
This operator appends one or more lines to the current point. Each set of 2 operands is interpreted by original
rlineto operator syntax.
4.4.2.1.4 Relative-relative lineto (rrcurveto)
The original syntax of this operator in Type 1 glyph shape representation is described in 2.7.3.2.7.
* {dxa dya dxb dyb dxc dyc}+ rrcurveto (00/08) *
This operator in Open Type 3 glyph shape representation appends one or more Bézier curves to the current
point. Each set of 6 operands is interpreted by original rrcurveto operator syntax described in 2.7.3.2.7.
4.4.2.1.5 Vertical-horizontal curveto (vhcurveto)
The original syntax of this operator in Type 1 glyph shape representation is described in 2.7.3.2.8. This
operator in Open Type 3 glyph shape representation is interpreted by most appropriate syntax in following
syntaxes:
* dy1 dx2 dy2 dx3 dyf? vhcurveto (01/14) *
* dy1 dx2 dy2 dx3 {dxa dxb dyb dyc dyd dxe dye dxf}+ dyf? vhcurveto (01/14) *
* {dya dxb dyb dxc dxd dxe dye dyf}+ dxf? vhcurveto (01/14)
and appends one or more Bézier curves to the current point. The syntax is same as enhanced hvcurveto
except x, y coordinates are exchanged for initial and final curves.
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ISO/IEC 9541-3:1994/Amd.2:2009(E)
4.4.2.1.6 Vertical lineto (vlineto)
The original syntax of this operator in Type 1 glyph shape representation is described in 2.7.3.2.9. This
operator in Open Type 3 glyph shape representation is interpreted by most appropriate syntax in following
syntaxes:
* dy1 dx2 . dyN vlineto (00/07) *
* dy1 dx2 . dyN dx(N+1) vlineto (00/07) *
and appends the alternating vertical and horizontal line from the current point. The first line is vertical and the
second line is horizontal (specified by only dx1).
4.4.2.2 Enhanced hint operators
In Type 1 glyph shape representation, the following operators take two operands that specifies the zone to
apply the hinting parameter. To set hinting parameters to parallel lines, the following operaters are enhanced
to take multiple sets of operands.
4.4.2.2.1 Hori
...