ISO/IEC 14496-22:2007
(Main)Information technology — Coding of audio-visual objects — Part 22: Open Font Format
Information technology — Coding of audio-visual objects — Part 22: Open Font Format
ISO/IEC 14496-22:2007, "Open Font Format Specification", defines the extensible font data format representation for interchange of digital font information in different multimedia applications. Historically, scalable digital fonts have come in two basic flavours: PostScript (registered trademark of Adobe Systems Incorporated) Type 1 and TrueType (trademark of Apple Computer Incorporated). Both of them are multi-platform outline font standards. OpenType (registered trademark of Microsoft Corporation) is the unification of these two most powerful and widely used font formats, PostScript and TrueType, into a single font format. Designed to handle languages with complex typographic requirements, such as Arabic, it supports alternate glyphs and contextual ligature substitution. ISO/IEC 14496-22:2007 defines the data format for scalable digital fonts that is based on the OpenType specification, version 1.4. ISO/IEC 14496-22 addresses the following goals: high-quality scaling of glyphs, based on the advanced TrueType hinting capabilities; broader multi-platform support; better support for international character sets and the Unicode standard; better protection for font data using digital signatures in font files; smaller file sizes to make font distribution more efficient; broader support for advanced typographic features and text layout.
Technologies de l'information — Codage des objets audiovisuels — Partie 22: Format de police de caractères ouvert
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INTERNATIONAL ISO/IEC
STANDARD 14496-22
First edition
2007-03-15
Information technology — Coding of
audio-visual objects —
Part 22:
Open Font Format
Technologies de l'information — Codage des objets audiovisuels —
Partie 22: Format de police de caractères ouvert
Reference number
ISO/IEC 14496-22:2007(E)
©
ISO/IEC 2007
---------------------- Page: 1 ----------------------
ISO/IEC 14496-22:2007(E)
PDF disclaimer
This PDF file may contain embedded typefaces. In accordance with Adobe's licensing policy, this file may be printed or viewed but
shall not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading this file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create this PDF file can be found in the General Info relative to the file; the PDF-creation
parameters were optimized for printing. Every care has been taken to ensure that the file is suitable for use by ISO member bodies. In
the unlikely event that a problem relating to it is found, please inform the Central Secretariat at the address given below.
© ISO/IEC 2007
All rights reserved. Unless otherwise specified, 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 either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
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Published in Switzerland
ii © ISO/IEC 2007 — All rights reserved
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ISO/IEC 14496-22:2007(E)
Contents Page
Foreword. v
Introduction . vii
1 Scope . 1
2 Normative References. 2
3 The Open Font File Format . 2
3.1 Description . 2
3.2 Filenames . 2
3.3 Data Types. 2
3.4 Table Version Numbers. 3
3.5 Open Font Structure. 4
3.6 TrueType Collections . 6
4 Open Font Tables. 8
4.1 General. 8
4.2 Required Common Tables . 8
4.3 TrueType OutlineTables. 50
4.4 PostScript Outline Tables . 55
4.5 Bitmap Glyph Tables . 57
4.6 Optional Tables. 69
5 Advanced Open Font Layout Tables .93
5.1 Advanced Open Font Layout Extensions. 93
5.2 OFF Layout Common Table Formats. 98
5.3 Advanced Typographic Tables. 120
5.4 Layout Tag Registry . 263
6 Recommendations for OFF Fonts. 338
7 General Recommendations . 343
7.1 Optimized Table Ordering. 343
7.2 Non-Standard (Symbol) Fonts. 343
7.3 Device Resolutions. 343
7.4 Baseline to Baseline Distances. 344
7.5 Style Bits. 345
7.6 Drop-out Control. 345
7.7 Embedded Bitmaps . 345
7.8 OFF CJK Font Guidelines . 345
Annex A (informative) Patent Statements. 346
Annex B (informative) Font Class and Font Subclass parameters . 347
B.1 Introduction . 347
B.2 sFamilyClass . 347
B.3 Class ID=0 No Classification . 347
B.4 Class ID=1 Oldstyle Serifs . 347
B.5 Class ID=2 Transitional Serifs . 349
B.6 Class ID=3 Modern Serifs. 349
B.7 Class ID=4 Clarendon Serifs. 350
B.8 Class ID=5 Slab Serifs. 351
B.9 Class ID=6 (reserved for future use). 352
B.10 Class ID=7 Freeform Serifs. 352
B.11 Class ID=8 Sans Serifs. 353
B.12 Class ID=9 Ornamentals. 354
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ISO/IEC 14496-22:2007(E)
B.13 Class ID=10 Scripts. 355
B.14 Class ID=11 (reserved for future use) . 356
B.15 Class ID=12 Symbolic. 357
B.16 Class ID=13 Reserved. 358
B.17 Class ID=14 Reserved. 358
Annex C (informative) Earlier versions of OS/2 – OS/2 and Windows Metrics . 359
C.1 OS/2 - OS/2 and Windows Metrics (Version 0). 359
C.2 OS/2 - OS/2 and Windows Metrics (Version 1). 379
C.3 OS/2 - OS/2 and Windows Metrics (Version 2). 404
Bibliography . 426
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ISO/IEC 14496-22:2007(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.
ISO/IEC 14496-22 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
ISO/IEC 14496 consists of the following parts, under the general title Information technology — Coding of
audio-visual objects:
⎯ Part 1: Systems
⎯ Part 2: Visual
⎯ Part 3: Audio
⎯ Part 4: Conformance testing
⎯ Part 5: Reference software
⎯ Part 6: Delivery Multimedia Integration Framework (DMIF)
⎯ Part 7: Optimized reference software for coding of audio-visual objects [Technical Report]
⎯ Part 8: Carriage of ISO/IEC 14496 contents over IP networks
⎯ Part 9: Reference hardware description [Technical Report]
⎯ Part 10: Advanced Video Coding
⎯ Part 11: Scene description and application engine
⎯ Part 12: ISO base media file format
⎯ Part 13: Intellectual Property Management and Protection (IPMP) extensions
⎯ Part 14: MP4 file format
⎯ Part 15: Advanced Video Coding (AVC) file format
⎯ Part 16: Animation Framework eXtension (AFX)
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ISO/IEC 14496-22:2007(E)
⎯ Part 17: Streaming text format
⎯ Part 18: Font compression and streaming
⎯ Part 19: Synthesized texture stream
⎯ Part 20: Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF)
⎯ Part 21: MPEG-J Graphics Framework eXtension (GFX)
⎯ Part 22: Open Font Format
⎯ Part 23: Symbolic Music Representation
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ISO/IEC 14496-22:2007(E)
Introduction
The International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC)
draw attention to the fact that it is claimed that compliance with this document may involve the use of a patent.
The ISO and IEC take no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured ISO and IEC that he is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect,
the statement of the holder of this patent right is registered with ISO and IEC. Information may be obtained
from the companies listed in Annex A.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights other than those identified in Annex A. ISO and IEC shall not be held responsible for identifying any or
all such patent rights.
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INTERNATIONAL STANDARD ISO/IEC 14496-22:2007(E)
Information technology — Coding of audio-visual objects —
Part 22:
Open Font Format
1 Scope
1)
This International Standard specifies the Open Font Format (OFF) specification, the TrueType™ and
Compact Font Format (CFF) outline formats, and the TrueType hinting language. Many references to both
2)
TrueType and PostScript® exist throughout this document, as Open Font Format fonts combine the two
technologies.
3)
NOTE This International Standard is based on the OpenType® version 1.4 font format specification, and is
technically equivalent to that specification.
Multimedia applications require a broad range of media-related standards. In addition to the typical audio and
video applications, multimedia presentations include scalable 2D graphics and text supporting all languages of
the world. Faithful reproduction of scalable multimedia content requires additional components including
scalable font technology. The Open Font Format is an extension of the TrueType font format, adding support
for PostScript font data. OFF fonts and the operating system services which support OFF fonts provide users
with a simple way to install and use fonts, whether the fonts contain TrueType outlines or CFF (PostScript)
outlines.
The Open Font Format addresses the following goals:
⎯ broader multi-platform support;
⎯ excellent support for international character sets;
⎯ excellent protection for font data;
⎯ smaller file sizes to make font distribution more efficient;
⎯ excellent support for advanced typographic control.
PostScript data included in OFF fonts may be directly rasterized or converted to the TrueType outline format
for rendering, depending on which rasterizers have been installed in the host operating system. But the user
model is the same: OFF fonts just work. Users will not need to be aware of the type of outline data in OFF
fonts. And font creators can use whichever outline format they feel provides the best set of features for their
work, without worrying about limiting a font's usability.
OFF fonts can include the OFF Layout tables, which allow font creators to design broader international and
high-end typographic fonts. The OFF Layout tables contain information on glyph substitution, glyph positioning,
justification and baseline positioning, enabling text-processing applications to improve text layout.
1) TrueType is a trademark of Apple Computer Incorporated.
2) PostScript is a registered trademark of Adobe Systems Incorporated.
3) OpenType is a registered trademark of Microsoft Corporation.
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ISO/IEC 14496-22:2007(E)
As with TrueType fonts, OFF fonts allow the handling of large glyph sets using Unicode encoding. Such
encoding allows broad international support, as well as support for typographic glyph variants.
Additionally, OFF fonts may contain digital signatures, which allow operating systems and browsing
applications to identify the source and integrity of font files, including embedded font files obtained in web
documents, before using them. Also, font developers can encode embedding restrictions in OFF fonts which
cannot be altered in a font signed by the developer.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO/IEC 10646, Information technology — Universal Multiple-Octet Coded Character Set (UCS)
ISO/IEC 14496-18, Information technology — Coding of audio-visual objects — Part 18: Font compression
and streaming
TrueType Instruction Set, http://www.microsoft.com/typography/otspec/ttinst.htm
Unicode 4.1.0, http://www.unicode.org/versions/Unicode4.1.0/
3 The Open Font File Format
3.1 Description
An Open font file contains data, in table format, that comprises either a TrueType or a PostScript outline font.
Rasterizers use combinations of data from the tables contained in the font to render the TrueType or
PostScript glyph outlines. Some of this supporting data is used no matter which outline format is used; some
of the supporting data is specific to either TrueType or PostScript.
3.2 Filenames
OFF fonts may have the extension .OTF or .TTF, depending on the kind of outlines in the font and the
creator's desire for compatibility on systems without native OFF support.
• In all cases, fonts with only CFF data (no TrueType outlines) always have an .OTF extension.
• Fonts containing TrueType outlines may have either .OTF or .TTF, depending on the desire for
backward compatibility on older systems or with previous versions of the font. TrueType Collection
fonts should have a .TTC extension whether or not the fonts have OFF layout tables present.
3.3 Data Types
The following data types are used in the OFF font file. All OFF fonts use big-endian (network byte order):
Data Type Description
BYTE 8-bit unsigned integer.
CHAR 8-bit signed integer.
USHORT 16-bit unsigned integer.
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ISO/IEC 14496-22:2007(E)
SHORT 16-bit signed integer.
ULONG 32-bit unsigned integer.
LONG 32-bit signed integer.
Fixed 32-bit signed fixed-point number (16.16)
FUNIT Smallest measurable distance in the em space.
FWORD 16-bit signed integer (SHORT) that describes a quantity in
FUnits.
UFWORD 16-bit unsigned integer (USHORT) that describes a quantity
in FUnits.
F2DOT14 16-bit signed fixed number with the low 14 bits of fraction
(2.14).
Date represented in number of seconds since 12:00
LONGDATETIME
midnight, January 1, 1904. The value is represented as a
signed 64-bit integer.
Tag Array of four uint8s (length = 32 bits) used to identify a
script, language system, feature, or baseline
GlyphID Glyph index number, same as uint16(length = 16 bits)
Offset Offset to a table, same as uint16 (length = 16 bits), NULL
Offset = 0x0000
The F2DOT14 format consists of a signed, 2's complement mantissa and an unsigned fraction. To compute
the actual value, take the mantissa and add the fraction. Examples of 2.14 values are:
Decimal Value Hex Value Mantissa Fraction
1.999939 0x7fff 1 16383/16384
1.75 0x7000 1 12288/16384
0.000061 0x0001 0 1/16384
0.0 0x0000 0 0/16384
-0.000061 0xffff -1 16383/16384
-2.0 0x8000 -2 0/16384
3.4 Table Version Numbers
Most tables have version numbers, and the version number for the entire font is contained in the Table
Directory. It should be noted that there are two different table version number types, each with its own
numbering scheme. USHORT version numbers always start at zero (0). Fixed version numbers start at one
(1.0 or 0x00010000), except where noted (EBDT, EBLC and EBSC tables).
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ISO/IEC 14496-22:2007(E)
Implementations reading tables must include code to check version numbers so that if and when the format
and therefore the version number changes, older implementations will reject newer versions gracefully, if the
changes are incompatible.
When a Fixed number is used as a version, the upper 16 bits comprise a major version number, and the lower
16 bits a minor. Tables with non-zero minor version numbers always specify the literal value of the version
number since the normal representation of Fixed numbers is not necessarily followed. For example, the
version number of 'maxp' table version 0.5 is 0x00005000, and that of 'vhea' table version 1.1 is 0x00011000.
If an implementation understands a major version number, then it can safely proceed reading the table. The
minor version number indicates extensions to the format that are undetectable by implementations that do not
support them.
The only exception to this is the Offset Table's sfnt version. This serves solely to identify whether the OFF font
contains TrueType outlines (a value of 1.0) or CFF data (the tag 'OTTO'), as described in subclause 3.5,
'Open Font Structure.'
When a USHORT number is used to indicate version, it should be treated as though it were a minor version
number; i.e., all format changes are compatible extensions.
3.5 Open Font Structure
A key characteristic of the OFF format is the TrueType sfnt "wrapper", which provides organization for a
collection of tables in a general and extensible manner.
The OFF font with the Offset Table. If the font file contains only one font, the Offset Table will begin at byte 0
of the file. If the font file is a TrueType collection, the beginning point of the Offset Table for each font is
indicated in the TTCHeader.
Offset Table
Type Name Description
Fixed sfnt version 0x00010000 for version 1.0 or 'OTTO'.
USHORT numTables Number of tables.
USHORT searchRange (Maximum power of 2 <= numTables) x 16.
USHORT entrySelector Log2(maximum power of 2 <= numTables).
USHORT rangeShift NumTables x 16-searchRange.
OFF fonts that contain TrueType outlines should use the value of 1.0 for the sfnt version. OFF fonts containing
CFF data should use the tag 'OTTO' as the sfnt version number.
3.5.1 Table Directory
The Offset Table is followed immediately by the Table Directory entries. Entries in the Table Directory must be
sorted in ascending order by tag. Offset values in the Table Directory are measured from the start of the font
file.
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ISO/IEC 14496-22:2007(E)
Table Directory
Type Name Description
ULONG tag 4 -byte identifier.
ULONG checkSum CheckSum for this table.
ULONG Offset Offset from beginning of TrueType font file.
ULONG length Length of this table.
The Table Directory makes it possible for a given font to contain only those tables it actually needs. As a result
there is no standard value for numTables.
Tags are the names given to tables in the OFF font file. All tag names consist of four characters. Names with
less than four letters are allowed if followed by the necessary trailing spaces. All tag names defined within a
font (e.g., table names, feature tags, language tags) must be built from printing characters represented by
ASCII values 32-126.
NOTE Tag names are case sensitive.
3.5.2 Calculating Checksums
Table checksums are the unsigned sum of the longs of a given table. In C, the following function can be used
to determine a checksum:
ULONG
CalcTableChecksum(ULONG *Table, ULONG Length)
{
ULONG Sum = 0L;
ULONG *Endptr = Table+((Length+3) & ~3) / sizeof(ULONG);
while (Table < EndPtr)
Sum += *Table++;
return Sum;
}
NOTE This function implies that the length of a table must be a multiple of four bytes. In fact, a font is not considered
structurally proper without the correct padding. All tables must begin on four byte boundries, and any remaining space
between tables is padded with zeros. The length of all tables should be recorded in the table directory with their actual
length (not their padded length).
To calculate the checkSum for the 'head' table which itself includes the checkSumAdjustment entry for the
entire font, do the following:
1. Set the checkSumAdjustment to 0.
2. Calculate the checksum for all the tables including the 'head' table and enter that value into the table
directory.
3. Calculate the checksum for the entire font.
4. Subtract that value from the hex value B1B0AFBA.
5. Store the result in checkSumAdjustment.
The checkSum for the head table which includes the checkSumAdjustment entry for the entire font is now
incorrect. That is not a problem. Do not change it. An application attempting to verify that the 'head' table has
not changed should calculate the checkSum for that table by not including the checkSumAdjustment value,
and compare the result with the entry in the table directory.
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ISO/IEC 14496-22:2007(E)
3.6 TrueType Collections
A TrueType Collection (TTC) is a means of delivering multiple OFF fonts in a single file structure. TrueType
Collections are most useful when the fonts to be delivered together share many glyphs in common. By
allowing multiple fonts to share glyph sets, TTCs can result in a significant saving of file space.
For example, a group of Japanese fonts may each have their own designs for the kana glyphs, but share
identical designs for the kanji. With ordinary OFF font files, the only way to include the common kanji glyphs is
to copy their glyph data into each font. Since the kanji represent much more data than the kana, this results in
a great deal of wasteful duplication of glyph data. TTCs were defined to solve this problem.
The CFF rasterizer does not currently support TTC files.
3.6.1 The TTC File Structure
The TTC File Structure
A TrueType Collection file consists of a single TTC Header table, one or more Offset Tables with Table
Directories, and a number of OFF tables. The TTC Header must be located at the beginning of the TTC file.
The TTC file must contain a complete Offset Table and Table Directory for each font. A TTC file Table
Directory has exactly the same format as a TTF file Table Directory. The table Offsets in all Table Directories
within a TTC file are measured from the beginning of the TTC file.
Each OFF table in a TTC file is referenced through the Offset Table and Table Directory of each font which
uses that table. Some of the OFF tables must appear multiple times, once for each font included in the TTC;
while other tables may be shared by multiple fonts in the TTC.
As an example, consider a TTC file which combines two Japanese fonts (Font1 and Font2). The fonts have
different kana designs (Kana1 and Kana2) but use the same design for kanji. The TTC file contains a single
'glyf' table which includes both designs of kana together with the kanji; both fonts' Table Directories point to
this 'glyf' table. But each font's Table Directory points to a different 'cmap' table, which identifies the glyph set
to use. Font1's 'cmap' table points to the Kana1 region of the 'loca' and 'glyf' tables for kana glyphs, and to the
kanji region for the kanji. Font2's 'cmap' table points to the Kana2 region of the 'loca' and 'glyf' tables for kana
glyphs, and to the same kanji region for the kanji.
The tables that should have a unique copy per font are those that are used by the system in identifying the
font and its character mapping, including 'cmap', 'name', and 'OS/2'. The tables that should be shared by fonts
in the TTC are those that define glyph and instruction data or use glyph indices to access data: 'glyf', 'loca',
'hmtx', 'hdmx', 'LTSH', 'cvt ', 'fpgm', 'prep', 'EBLC', 'EBDT', 'EBSC', 'maxp', and so on. In practice, any tables
which have identical data for two or more fonts may be shared.
NOTE Tools are available to help build .TTC files. The process involves paying close attention the issue of glyph
renumbering in a font and the side effects that can result, in the 'cmap' table and elsewhere. The fonts to be merged must
also have compatible TrueType instructions-that is, the
...
INTERNATIONAL ISO/IEC
STANDARD 14496-22
First edition
2007-03-15
Information technology — Coding of
audio-visual objects —
Part 22:
Open Font Format
Technologies de l'information — Codage des objets audiovisuels —
Partie 22: Format de police de caractères ouvert
Reference number
ISO/IEC 14496-22:2007(E)
©
ISO/IEC 2007
---------------------- Page: 1 ----------------------
ISO/IEC 14496-22:2007(E)
PDF disclaimer
PDF files may contain embedded typefaces. In accordance with Adobe's licensing policy, such files may be printed or viewed but shall
not be edited unless the typefaces which are embedded are licensed to and installed on the computer performing the editing. In
downloading a PDF file, parties accept therein the responsibility of not infringing Adobe's licensing policy. The ISO Central Secretariat
accepts no liability in this area.
Adobe is a trademark of Adobe Systems Incorporated.
Details of the software products used to create the PDF file(s) constituting this document can be found in the General Info relative to
the file(s); the PDF-creation parameters were optimized for printing. Every care has been taken to ensure that the files are suitable for
use by ISO member bodies. In the unlikely event that a problem relating to them is found, please inform the Central Secretariat at the
address given below.
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can be viewed using Adobe® Acrobat® Reader.
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© ISO/IEC 2007
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...
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