OpenType is a format for scalable
computer fontA computer font is an electronic data file containing a set of glyphs, characters, or symbols such as dingbats. Although the term font first referred to a set of metal type sorts in one style and size, since the 1990s it is generally used to refer to a scalable set of digital shapes that may be...
s. It was built on its predecessor
TrueTypeTrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript...
, retaining TrueType's basic structure and adding many intricate data structures for prescribing
typographicTypography is the art and technique of arranging type in order to make language visible. The arrangement of type involves the selection of typefaces, point size, line length, leading , adjusting the spaces between groups of letters and adjusting the space between pairs of letters...
behavior. OpenType is a registered trademark of Microsoft Corporation.
The specification germinated at Microsoft, with
Adobe SystemsAdobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
also contributing by the time of the public announcement in 1996. The specification continues to be developed actively and is presently migrating to an open format.
Because of wide availability and typographic flexibility, including provisions for handling the diverse behaviors of all the world's
writing systemA writing system is a symbolic system used to represent elements or statements expressible in language.-General properties:Writing systems are distinguished from other possible symbolic communication systems in that the reader must usually understand something of the associated spoken language to...
s, OpenType fonts are used commonly today on the major computer platforms.
History
OpenType's origins date to Microsoft's attempt to license
AppleApple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
's advanced typography technology
GX TypographyApple Advanced Typography is Apple Inc's computer software for advanced font rendering, supporting internationalization and complex features for typographers, a successor to Apple's little-used QuickDraw GX font technology of the mid-1990s...
in the early 1990s. Those negotiations failed, motivating Microsoft to forge ahead with its own technology, dubbed "TrueType Open" in 1994. Adobe joined Microsoft in those efforts in 1996, adding support for the glyph outline technology used in its Type 1 fonts.
These efforts were intended by Microsoft and Adobe to supersede both Apple's
TrueTypeTrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript...
and Adobe's Type 1 ("
PostScriptPostScript is a dynamically typed concatenative programming language created by John Warnock and Charles Geschke in 1982. It is best known for its use as a page description language in the electronic and desktop publishing areas. Adobe PostScript 3 is also the worldwide printing and imaging...
") font formats. Needing a more expressive font format to handle fine typography and the complex behavior of many of the world's writing systems, the two companies combined the underlying technologies of both formats and added new extensions intended to address those formats' limitations. The name OpenType was chosen for the combined technologies, and the technology was announced later that year.
Open Font Format
Adobe and Microsoft continued to develop and refine OpenType over the next decade. Then, in late 2005, OpenType began migrating to an open standard under the
International Organization for StandardizationThe International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
(ISO) within the MPEG group, which had previously (in 2003) adopted OpenType 1.4 by reference for
MPEG-4MPEG-4 is a method of defining compression of audio and visual digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group under the formal standard ISO/IEC...
. Adoption of the new standard reached formal approval in March 2007 as ISO Standard ISO/IEC 14496-22 (MPEG-4 Part 22) called
Open Font Format (OFF). It is also sometimes referred to as "Open Font Format Specification" (OFFS). The standard is technically equivalent to OpenType 1.4 specification, with appropriate language changes for ISO. The second edition of the Open Font Format was published in 2009 (ISO/IEC 14496-22:2009) and it is declared as "technically equivalent" to the "OpenType font format specification". It is a free, publicly available standard.
By 2001 hundreds of OpenType fonts were on the market. Adobe finished converting their entire font library to OpenType toward the end of 2002. , around 10,000 OpenType fonts had become available, with the Adobe library comprising about a third of the total. By 2006, every major
font foundryA type foundry is a company that designs or distributes typefaces. Originally, type foundries manufactured and sold metal and wood typefaces and matrices for line-casting machines like the Linotype and Monotype machines designed to be printed on letterpress printers...
and many minor ones were developing fonts in OpenType format.
Description
OpenType uses the general
sfntSfnt is a font file format used for PostScript, TrueType and OpenType fonts. Sfnt stands for spline font, and was originally developed for Apple Computer's QuickDraw....
structure of a TrueType font, but it adds several smartfont options that enhance the font's typographic and language support capabilities.
The
glyphA glyph is an element of writing: an individual mark on a written medium that contributes to the meaning of what is written. A glyph is made up of one or more graphemes....
outline data in an OpenType font may be in one of two formats: either TrueType format outlines in a 'glyf' table, or Compact Font Format (CFF) outlines in a 'CFF ' table. (The table name 'CFF ' is four characters long, ending in a space character.) CFF outline data is based on the
PostScriptPostScript is a dynamically typed concatenative programming language created by John Warnock and Charles Geschke in 1982. It is best known for its use as a page description language in the electronic and desktop publishing areas. Adobe PostScript 3 is also the worldwide printing and imaging...
language Type 2 font format. However, the OpenType specification does not support the use of PostScript outlines in a TrueType Collection font file.
For many purposes, such as layout, it doesn't matter what the outline data format is, but for some purposes, such as
rasterisationRasterisation is the task of taking an image described in a vector graphics format and converting it into a raster image for output on a video display or printer, or for storage in a bitmap file format....
, it is significant. The OpenType standard does not specify the outline data format: rather, it accomommodates any of several existing standards. Sometimes terms like "OpenType (PostScript flavor)", "Type 1 OpenType", "OpenType CFF", or "OpenType (TrueType flavor)" are used to indicate which outline format a particular OpenType font file contains.
OpenType has several distinctive characteristics:
- Accommodates the Unicode
Unicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
character encodingA character encoding system consists of a code that pairs each character from a given repertoire with something else, such as a sequence of natural numbers, octets or electrical pulses, in order to facilitate the transmission of data through telecommunication networks or storage of text in...
(as well as others), so that it can support any writing script (or multiple scripts at once).
- Accommodates up to 65,536 glyphs.
- Advanced typographic "layout" features which prescribe positioning and replacement of rendered glyphs. Replacement features include ligatures; positioning features include kerning
In typography, kerning is the process of adjusting the spacing between characters in a proportional font, usually to achieve a visually pleasing result. Kerning is the adjustment of the space between individual letter forms vs. tracking which is the uniform adjustment of spacing applied over a...
, mark placement, and baselineIn European and West Asian typography and penmanship, the baseline is the line upon which most letters "sit" and below which descenders extend.In the example to the right, the letter 'p' has a descender; the other letters sit on the baseline....
specification.
- Cross-platform font files, which can be used without modification on Mac OS, Windows and Unix systems.
- If no additional glyphs or extensive typographic features are added, OpenType CFF fonts can be considerably smaller than their Type 1 counterparts.
Comparison to other formats
Compared with
Apple ComputerApple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
’s "GX Typography"—now called
Apple Advanced TypographyApple Advanced Typography is Apple Inc's computer software for advanced font rendering, supporting internationalization and complex features for typographers, a successor to Apple's little-used QuickDraw GX font technology of the mid-1990s...
(AAT)—and with the
SILSIL International is a U.S.-based, worldwide, Christian non-profit organization, whose main purpose is to study, develop and document languages, especially those that are lesser-known, in order to expand linguistic knowledge, promote literacy, translate the Christian Bible into local languages,...
’s
GraphiteGraphite is a programmable Unicode-compliant smart-font technology and rendering system developed by SIL International. It is free software, distributed under the terms of the GNU Lesser General Public License and the Common Public License....
technology, OpenType is less flexible in typographic options, but superior in language-related options and support.
OpenType has been much more successful than AAT and Graphite. There are many more fonts and supporting applications, despite AAT being an older technology. The single-platform nature of AAT and the lack of support from any major software vendor other than Apple itself are both likely factors in this. The
free softwareFree software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
Graphite technology has recently been packaged with the desktop publishing and document editing software,
LibreOfficeLibreOffice is a free and open source office suite developed by The Document Foundation as a fork of OpenOffice.org. It is largely compatible with other major office suites, including Microsoft Office, and available on a variety of platforms...
(It is included in both the Windows and Linux distributions, but not with Mac, as AAT is already present).
From a font developer’s perspective, OpenType is, for many common situations, easier to develop for than AAT or Graphite. First, the simple declarative substitutions and positioning of OpenType are more readily understood than AAT’s more complex state tables or the Graphite description language that resembles
C syntaxThe syntax of the C programming language is a set of rules that specifies whether the sequence of characters in a file is conforming C source code...
. Second, Adobe’s strategy of licensing at no charge the
source codeIn computer science, source code is text written using the format and syntax of the programming language that it is being written in. Such a language is specially designed to facilitate the work of computer programmers, who specify the actions to be performed by a computer mostly by writing source...
developed for its own font development, AFDKO (Adobe Font Development Kit for OpenType), allowed third-party font editing applications such as
FontLabFontLab is both the name of a company, FontLab Ltd, and the former name of their flagship font editor product, now called FontLab Studio. Since the early 2000s, FontLab Studio has been the dominant software tool for commercial/retail digital font development. This is partly because the...
and FontMaster to add support with relative ease. Although Adobe’s text-driven coding support is not as visual as Microsoft’s separate tool, VOLT (Visual OpenType Layout Tool), the integration with the tools being used to make the fonts has been well received.
Another difference is that an OpenType support framework (such as Microsoft’s
UniscribeUniscribe is the Microsoft Windows set of services for rendering Unicode-encoded text, especially complex text layout. They are implemented in the DLL USP10.DLL. USP10.dll became available to the public with Windows 2000 and Internet Explorer 5.0...
) needs to provide a fair bit of knowledge about special language processing issues to handle (for example: Arabic). With AAT or Graphite, the font developer has to encapsulate all that expertise in the font. This means that AAT and Graphite can handle any arbitrary language, but that it requires more work and expertise from the font developers. On the other hand, OpenType fonts are easier to make, but can only support
complex text layoutComplex text layout or complex text rendering refers to the typesetting of writing systems which require complex transformations between text input and text display for proper rendering on the screen or the printed page...
if the application or operating system knows how to handle them.
Prior to supporting OpenType, Adobe promoted
multiple master fontsMultiple master fonts are an extension to Adobe Systems' Type 1 PostScript fonts, now mostly superseded by the advent of OpenType...
and expert fonts for high-end typography. Multiple master fonts lacked the controls for alternate glyphs and languages provided by OpenType, but provided smooth transitions between styles within a type family. Expert fonts were intended as supplementary fonts, such that all the special characters that had no place in the Adobe Standard Encoding character set – ligatures, fractions, small capitals, etc. – were placed in the expert font instead. Usage in applications was tricky, with, for example, typing a
Z causing the
ffl ligature to be generated. In modern OpenType fonts all these glyphs are encoded with their Unicode indices and selection method (i.e. under what circumstances that glyph should be used).
Basic Roman support
OpenType support may be divided into several categories. Virtually all applications and most modern operating systems have basic Roman support and work with OpenType fonts just as well as other, older formats. What is of particular interest apart from basic Roman support is: extended language support through
UnicodeUnicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
, support for complex writing scripts such as
ArabicArabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
and the
Indic languagesThe Indo-Aryan languages constitutes a branch of the Indo-Iranian languages, itself a branch of the Indo-European language family...
, and advanced typographic support for
Latin scriptThe Latin alphabet, also called the Roman alphabet, is the most recognized alphabet used in the world today. It evolved from a western variety of the Greek alphabet called the Cumaean alphabet, which was adopted and modified by the Etruscans who ruled early Rome...
languages such as
EnglishEnglish is a West Germanic language that arose in the Anglo-Saxon kingdoms of England and spread into what was to become south-east Scotland under the influence of the Anglian medieval kingdom of Northumbria...
.
Amongst Microsoft's operating systems, OpenType TT fonts (.TTF) are backward compatible and therefore supported by all
WindowsMicrosoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
versions starting with Windows 3.1. OpenType PS fonts (.OTF) are supported in all Windows versions starting with
Windows 2000Windows 2000 is a line of operating systems produced by Microsoft for use on personal computers, business desktops, laptops, and servers. Windows 2000 was released to manufacturing on 15 December 1999 and launched to retail on 17 February 2000. It is the successor to Windows NT 4.0, and is the...
;
Adobe Type ManagerAdobe Type Manager is the name of a family of computer programs created and marketed by Adobe Systems for use with their Type 1 fonts. The current version is Adobe ATM Light 4.1.2, available from Adobe's FTP .-Apple Macintosh:...
is required to be installed on Windows 95/98/NT/Me for basic Roman support (only) of OpenType PS fonts.
Extended language support
Extended language support via
UnicodeUnicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
for both OpenType and TrueType is present in most Windows applications (including Microsoft Office Publisher, most
AdobeAdobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
applications, and Microsoft Office 2003, though not Word 2002), CorelDRAW X3 and newer, and many Mac OS X applications, including Apple's own such as
TextEditTextEdit is a simple, open source word processor and text editor, first featured in NeXT's NEXTSTEP and OPENSTEP. It is now distributed with Mac OS X since Apple Inc.'s acquisition of NeXT, and available as a GNUstep application for other Unix-compatible operating systems such as Linux...
, Pages and Keynote. It is also widely supported in free operating systems, such as GNU/Linux (e.g. in multiplatform applications like
AbiwordAbiWord is a free and open source software word processor. It was originally started by SourceGear Corporation as the first part of a proposed AbiSuite. Development stopped when SourceGear changed their focus to Internet appliances. AbiWord was adopted by some open source developers and AbiWord...
,
GnumericGnumeric is a spreadsheet program that is part of the GNOME Free Software Desktop Project. Gnumeric version 1.0 was released December 31, 2001. Gnumeric is distributed as free software under the GNU GPL license; it is intended to replace proprietary and other spreadsheet programs such as Microsoft...
,
KOfficeCalligra Suite is a graphic art and office suite by KDE created from KOffice in 2010. It is available for desktop PCs, tablet computers, and smartphones...
,
ScribusScribus is a desktop publishing application, released under the GNU General Public License as free software. It is based on the free Qt toolkit, therefore native versions are available for Linux, Unix-like operating systems, Mac OS X, Microsoft Windows, and OS/2...
,
OpenOffice.orgOpenOffice.org, commonly known as OOo or OpenOffice, is an open-source application suite whose main components are for word processing, spreadsheets, presentations, graphics, and databases. OpenOffice is available for a number of different computer operating systems, is distributed as free software...
3.2 and later versions, etc.).
OpenType support for complex written scripts has so far mainly appeared in Microsoft applications in
Microsoft OfficeMicrosoft Office is a non-free commercial office suite of inter-related desktop applications, servers and services for the Microsoft Windows and Mac OS X operating systems, introduced by Microsoft in August 1, 1989. Initially a marketing term for a bundled set of applications, the first version of...
, such as
Microsoft WordMicrosoft Word is a word processor designed by Microsoft. It was first released in 1983 under the name Multi-Tool Word for Xenix systems. Subsequent versions were later written for several other platforms including IBM PCs running DOS , the Apple Macintosh , the AT&T Unix PC , Atari ST , SCO UNIX,...
and
Microsoft PublisherMicrosoft Publisher is a desktop publishing application from Microsoft. It is an entry-level application, differing from Microsoft Word in that the emphasis is placed on page layout and design rather than text composition and proofing...
.
Adobe InDesignAdobe InDesign is a software application produced by Adobe Systems. It can be used to create works such as posters, flyers, brochures, magazines, newspapers and books. In conjunction with Adobe Digital Publishing Suite InDesign can publish content suitable for tablet devices...
provides extensive OpenType capability in
Japaneseis a language spoken by over 130 million people in Japan and in Japanese emigrant communities. It is a member of the Japonic language family, which has a number of proposed relationships with other languages, none of which has gained wide acceptance among historical linguists .Japanese is an...
but does not directly support Middle Eastern or
Indic scriptsThe Brahmic or Indic scripts are a family of abugida writing systems. They are used throughout South Asia , Southeast Asia, and parts of Central and East Asia, and are descended from the Brāhmī script of the ancient Indian subcontinent...
— though a separate version of InDesign is available that supports Middle Eastern scripts such as Arabic and Hebrew. Undocumented functionality in many Adobe Creative Suite 4 applications, including InDesign, Photoshop and Illustrator, enables Middle Eastern, Indic and other languages, but is not officially supported by Adobe, and requires third-party plug-ins to provide a user interface for the features.
Advanced typography
Advanced typographic support for Latin script languages first appeared in Adobe applications such as
Adobe InDesignAdobe InDesign is a software application produced by Adobe Systems. It can be used to create works such as posters, flyers, brochures, magazines, newspapers and books. In conjunction with Adobe Digital Publishing Suite InDesign can publish content suitable for tablet devices...
,
Adobe PhotoshopAdobe Photoshop is a graphics editing program developed and published by Adobe Systems Incorporated.Adobe's 2003 "Creative Suite" rebranding led to Adobe Photoshop 8's renaming to Adobe Photoshop CS. Thus, Adobe Photoshop CS5 is the 12th major release of Adobe Photoshop...
and
Adobe IllustratorAdobe Illustrator is a vector graphics editor developed and marketed by Adobe Systems. Illustrator is similar in scope, intended market, and functionality to its competitors, CorelDraw, Xara Designer Pro and Macromedia FreeHand....
.
QuarkXPressQuarkXPress is a computer application for creating and editing complex page layouts in a WYSIWYG environment. It runs on Mac OS X and Windows. It was first released by Quark, Inc...
6.5 and below (
Quark, Inc.Quark, Inc. is a privately owned software company best known for QuarkXPress. It is called Quark because the company's goal is to "create software that would be the platform for publishing", just as quarks are the basis for all matter.As of August 2011, Quark's offerings include:* QuarkXPress -...
) were not
UnicodeUnicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
compliant. Hence text in these versions of QuarkXPress that contains anything other than WinANSI/
MacRomanMac OS Roman is a character encoding primarily used by Mac OS to represent text. It encodes 256 characters, the first 128 of which are identical to ASCII, with the remaining characters including mathematical symbols, diacritics, and additional punctuation marks. It is suitable for use to represent...
characters will not display correctly in an OpenType font (nor in other Unicode font formats, for that matter). However, in QuarkXPress 7, Quark offered support similar to Adobe's. Corel's
CorelDRAWCorelDRAW is a vector graphics editor developed and marketed by Corel Corporation of Ottawa, Canada. It is also the name of Corel's Graphics Suite...
does not support OpenType typographic features, either.
MellelMellel is a word processor for Mac OS X, developed since 2002 and marketed as especially suited for technical and academic writers. It is made by RedleX, a small software company from Israel. New features are added to the program every few months, many of which come from user suggestions...
, a Mac OS X-only word processor from Redlers, claims parity in typographic features with InDesign, but also extends the support to right-to-left scripts; so does the Classical Text Editor, a specialized word processor developed at the Austrian Academy of Sciences.
, popular Windows word processors did not support advanced OpenType typography features. Advanced typography features are implemented only in high-end
desktop publishingDesktop publishing is the creation of documents using page layout software on a personal computer.The term has been used for publishing at all levels, from small-circulation documents such as local newsletters to books, magazines and newspapers...
software. However, the text engine from
Windows Presentation FoundationDeveloped by Microsoft, the Windows Presentation Foundation is a computer-software graphical subsystem for rendering user interfaces in Windows-based applications. WPF, previously known as "Avalon", was initially released as part of .NET Framework 3.0. Rather than relying on the older GDI...
, which is a
managed codeManaged code is a term coined by Microsoft to identify computer program code that requires and will only execute under the "management" of a Common Language Runtime virtual machine ....
implementation of OpenType, is the first Windows
APIAn application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
to expose OpenType features to software developers, supporting both OpenType
TrueTypeTrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript...
, and OpenType CFF (Compact Font Format) fonts. It supports advanced typographic features such as ligatures,
old-style numeralsText figures are numerals typeset with varying heights in a fashion that resembles a typical line of running text, hence the name...
,
swashA swash is a typographical flourish on a glyph, like an exaggerated serif.Capital swash characters, which extended to the left, were historically often used to begin sentences. There were also minuscule swash characters, which came either extending to the left, to begin words, or to the right to...
variants,
fractionsA fraction represents a part of a whole or, more generally, any number of equal parts. When spoken in everyday English, we specify how many parts of a certain size there are, for example, one-half, five-eighths and three-quarters.A common or "vulgar" fraction, such as 1/2, 5/8, 3/4, etc., consists...
, superscript and subscript,
small capitalizationIn typography, small capitals are uppercase characters set at the same height and weight as surrounding lowercase letters or text figures...
,
glyph substitutionFont substitution is the process of using one font in place of another when the intended font either is not available or does not contain glyphs for the required characters.Font substitution can be aided by:...
, multiple
baselinesIn European and West Asian typography and penmanship, the baseline is the line upon which most letters "sit" and below which descenders extend.In the example to the right, the letter 'p' has a descender; the other letters sit on the baseline....
, contextual and stylistic alternate character forms,
kerningIn typography, kerning is the process of adjusting the spacing between characters in a proportional font, usually to achieve a visually pleasing result. Kerning is the adjustment of the space between individual letter forms vs. tracking which is the uniform adjustment of spacing applied over a...
, line-level
justificationIn typesetting, justification is the typographic alignment setting of text or images within a column or "measure" to align along both the left and right margin...
,
ruby characterare small, annotative glosses that can be placed above or to the right of a Chinese character when writing languages with logographic characters such as Chinese or Japanese to show the pronunciation...
s etc. WPF applications automatically gain support for advanced typography features. OpenType ligatures are accessible in Microsoft Office Word 2010.
Windows 7 introduced
DirectWriteDirectWrite is a text-layout and glyph-rendering API by Microsoft. It was designed to replace GDI/GDI+ and Uniscribe for screen-oriented rendering and was shipped with Windows 7 and Windows Server 2008 R2, as well as Windows Vista and Windows Server 2008 DirectWrite is a text-layout and...
, a hardware accelerated native
DirectXMicrosoft DirectX is a collection of application programming interfaces for handling tasks related to multimedia, especially game programming and video, on Microsoft platforms. Originally, the names of these APIs all began with Direct, such as Direct3D, DirectDraw, DirectMusic, DirectPlay,...
API for text rendering with support for multi-format text, resolution-independent outline fonts,
ClearTypeClearType is a trademark for Microsoft's implementation of subpixel rendering technology. ClearType attempts to improve the appearance of text on certain types of computer display screens by sacrificing color fidelity for additional intensity variation. This trade-off is asserted to work well on...
, advanced OpenType typography features, full Unicode text, layout and language support and low-level glyph rendering APIs.
On Mac OS X,
AATApple Advanced Typography is Apple Inc's computer software for advanced font rendering, supporting internationalization and complex features for typographers, a successor to Apple's little-used QuickDraw GX font technology of the mid-1990s...
-supporting applications running on Mac OS X 10.4 and later, including TextEdit and Keynote, get considerable OpenType support. Apple's support for OpenType in Mac OS X 10.4 included most advanced typographic features necessary for Latin script languages, such as
small capsIn typography, small capitals are uppercase characters set at the same height and weight as surrounding lowercase letters or text figures...
, oldstyle figures, and various sorts of ligatures, but it did not yet support contextual alternates, positional forms, nor glyph reordering as handled by Microsoft's Uniscribe library on Windows. Thus, Mac OS X 10.4 did not offer support for Arabic or Indic scripts via OpenType (though such scripts are fully supported by existing AAT fonts). Mac OS X 10.5 has improved support for OpenType and supports Arabic OpenType fonts.
Bitstream
PanoramaPanorama is a line layout and text composition engine to render text in various worldwide languages made by Bitstream Inc.. Panorama uses Font Fusion as the base to support rendering of the text...
, a line layout and text composition engine from
Bitstream Inc.Bitstream Inc. is a type foundry that produces digital typefaces . Founded in 1981 by Matthew Carter and Mike Parker among others, it claims to be the oldest such company...
, provides complete OpenType support for compact and standard Asian fonts, Arabic, Hebrew, Indic, Thai and over 50 other worldwide languages. The application supports key OpenType tables required for line layout, such as BASE, glyph definition (GDEF), glyph positioning (GPOS), and glyph substitution (GSUB). Panorama also offers complete support for advanced typography features, such as ligatures, swashes, small caps, ornaments, ordinals, superiors, old style, kerning, fractions, etc.
In
free softwareFree software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
environments such as
LinuxLinux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
, OpenType rendering is provided by the
FreeTypeFreeType is a software library written in C that implements a font rasterization engine. It is used to render text on to bitmaps and provides support for other font-related operations.-Details:...
project, included in free implementations of the
X Window SystemThe X window system is a computer software system and network protocol that provides a basis for graphical user interfaces and rich input device capability for networked computers...
such as Xorg. Complex text handling is provided either by
pangoPango is an LGPL licensed open source computing library used by software developers for laying out and rendering text in high quality, emphasising support for multilingual text...
or
QtQt is a cross-platform application framework that is widely used for developing application software with a graphical user interface , and also used for developing non-GUI programs such as command-line tools and consoles for servers...
. The
XeTeXXeTeX is a TeX typesetting engine using Unicode and supporting modern font technologies such as OpenType or Apple Advanced Typography...
system allows
TeXTeX is a typesetting system designed and mostly written by Donald Knuth and released in 1978. Within the typesetting system, its name is formatted as ....
documents to use OpenType fonts, along with most of their typographic features.
OpenType Feature File (.fea)
OpenType features are tedious to define using a GUI. Consequently, Adobe standardized a text specification format for feature files, which typically have a name ending in a
.fea extension. These files can be compiled into the binary font container (
.ttf or
.otf) using
Adobe FDKThe Adobe Font Development Kit for OpenType, also known as Adobe FDKO or simply AFDKO, is a set of command-line tools for editing and verifying OpenType fonts, freely-distributed by Adobe. It does not offer a glyph editor, but focuses on tools for manipulating font metrics, kerning and other...
(AFDKO),
FontLabFontLab is both the name of a company, FontLab Ltd, and the former name of their flagship font editor product, now called FontLab Studio. Since the early 2000s, FontLab Studio has been the dominant software tool for commercial/retail digital font development. This is partly because the...
or
FontForgeFontForge is a typeface editor program developed by George Williams. FontForge is free software and is distributed under the BSD license. FontForge is available for several operating systems and is localized in several languages.- Features :Fontforge supports many font formats, including...
. The latter program implements a few features that are documented in the Adobe standard but are not implemented by AFDKO.
Layout tags
OpenType Layout tags are 4-byte character strings that identify the scripts, language systems, features and baselines in an OpenType Layout font. Microsoft's Layout tag registry establishes conventions for naming and using these tags. OpenType features are created by using the tags in creating feature scripts that describe how characters are to be manipulated to make the desired feature. These feature scripts can be created and incorporated into OpenType fonts by advanced font editors such as
FontLab StudioFontLab is both the name of a company, FontLab Ltd, and the former name of their flagship font editor product, now called FontLab Studio. Since the early 2000s, FontLab Studio has been the dominant software tool for commercial/retail digital font development. This is partly because the...
, AsiaFont Studio, and
FontForgeFontForge is a typeface editor program developed by George Williams. FontForge is free software and is distributed under the BSD license. FontForge is available for several operating systems and is localized in several languages.- Features :Fontforge supports many font formats, including...
.
Operating system and application support for layout tags varies widely. A 2007 presentation summarizing the state of affairs was given by Jürgen Willrodt at TypoTechnica 2007.
Script tags
Script tags identify the scripts (writing systems) represented in an OpenType typeface. Each tag corresponds to contiguous character code ranges in Unicode. A script tag can consist of 4 or fewer lowercase letters, such as
for the
Arabic alphabetThe Arabic alphabet or Arabic abjad is the Arabic script as it is codified for writing the Arabic language. It is written from right to left, in a cursive style, and includes 28 letters. Because letters usually stand for consonants, it is classified as an abjad.-Consonants:The Arabic alphabet has...
,
for the
Cyrillic alphabetThe Cyrillic script or azbuka is an alphabetic writing system developed in the First Bulgarian Empire during the 10th century AD at the Preslav Literary School...
and
for the
Latin alphabetThe Latin alphabet, also called the Roman alphabet, is the most recognized alphabet used in the world today. It evolved from a western variety of the Greek alphabet called the Cumaean alphabet, which was adopted and modified by the Etruscans who ruled early Rome...
. The
math script tag, added by Microsoft for
Cambria MathCambria is part of the suite of fonts that comes with Microsoft Windows Vista, Windows 7, Microsoft Office 2007, Microsoft Office 2008 for Mac and Microsoft Office 2011 for Mac, specifically designed for on-screen reading and to be aesthetically pleasing when printed at small sizes. It is a...
, has been added to the specification.
Language system tags
Language system tags identify the language systems supported in an OpenType typeface. Examples include
ARA for
ArabicArabic is a name applied to the descendants of the Classical Arabic language of the 6th century AD, used most prominently in the Quran, the Islamic Holy Book...
,
ESP for
SpanishSpanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...
,
HYE for
ArmenianThe Armenian language is an Indo-European language spoken by the Armenian people. It is the official language of the Republic of Armenia as well as in the region of Nagorno-Karabakh. The language is also widely spoken by Armenian communities in the Armenian diaspora...
, etc. The codes are not in general the same as
ISO 639-2ISO 639-2:1998, Codes for the representation of names of languages — Part 2: Alpha-3 code, is the second part of the ISO 639 standard, which lists codes for the representation of the names of languages. The three-letter codes given for each language in this part of the standard are referred to as...
codes.
Feature tags
A list of OpenType features with expanded descriptions is given
list of typographic features.
Baseline tags
Baseline tags have a specific meaning when used in the horizontal writing direction (used in the 'BASE' table's HorizAxis table), vertical writing direction (used in the 'BASE' table's VertAxis table), or both.
| Baseline Tag |
HorizAxis |
VertAxis |
| 'hang' |
horizontal line from which the syllabograms seem to hang in the Tibetan scriptThe Tibetan alphabet is an abugida of Indic origin used to write the Tibetan language as well as the Dzongkha language, Denzongkha, Ladakhi language and sometimes the Balti language. The printed form of the alphabet is called uchen script while the hand-written cursive form used in everyday...
|
The same line in Tibetan vertical writing mode. |
| 'icfb' |
Ideographic character face bottom edge baseline. |
Ideographic character face left edge baseline. |
| 'icft' |
Ideographic character face top edge baseline. |
Ideographic character face right edge baseline. |
| 'ideo' |
Ideographic em-box bottom edge baseline. |
Ideographic em-box left edge baseline. |
| 'idtp' |
Ideographic em-box top edge baseline. |
Ideographic em-box right edge baseline. |
| 'math' |
The baseline about which mathematical characters are centered. |
The baseline about which mathematical characters are centered in vertical writing mode. |
| 'romn' |
The alphabetic baseline for characters rotated 90 degrees clockwise for vertical writing mode. |
SING gaiji solution
In 2005, Adobe shipped a new technology in their
Creative SuiteAdobe Creative Suite is a collection of graphic design, video editing, and web development applications made by Adobe Systems. The collection consists of Adobe's applications , that are based on various technologies...
applications bundle that offers a solution for the
gaiji (Japanese for "outside character") problem. Ideographic writing scripts such as Chinese and Japanese do not have fixed collections of characters. They use thousands of glyphs commonly and tens of thousands less commonly. Not all glyphs ever invented and used in Far Eastern literature have even been catalogued. A typical font might contain 8,000 to 15,000 of the most commonly used glyphs. From time to time, though, an author needs a glyph not present in the font of choice. Such missing characters are known in Japan as
gaiji, and they often disrupt work.
Another aspect of the
gaiji problem is that of variant glyphs for certain characters. Often certain characters have been written differently over periods of time. It is not unusual for place names or personal family names to use a historical form of a character. Thus it is possible for an end user using standard fonts to be left unable to spell correctly either their own name or the name of the place where they live.
Several ways to deal with
gaiji have been devised. Solutions that treat them as characters usually assign arbitrary Unicode values to them in the Private Use Area (PUA). Such characters cannot be used outside the environment in which the association of the private Unicode to the glyph shape is known. Documents based on them are not portable. Other installations treat
gaiji as graphics. This can be cumbersome because text layout and composition cannot apply to graphics. They cannot be searched for. Often their rendering looks different from surrounding characters because the machinery for rendering graphics usually is different from the machinery for rendering glyphs from fonts.
The SING (Smart INdependent Glyphlets) technology that made its debut with Adobe's Creative Suite 2 allows for the creation of glyphs, each packaged as a standalone font, after a fashion. Such a packaged glyph is called a
glyphlet. The format, which Adobe has made public, is based on OpenType. The package consists of the glyph outline in
TrueTypeTrueType is an outline font standard originally developed by Apple Computer in the late 1980s as a competitor to Adobe's Type 1 fonts used in PostScript...
or CFF (PostScript style outlines) form; standard OpenType tables declaring the glyph's metrics and behavior in composition; and metadata, extra information included for identifying the glyphlet, its ownership, and perhaps pronunciation or linguistic categorization. SING glyphlets can be created using
Fontlab'sFontLab is both the name of a company, FontLab Ltd, and the former name of their flagship font editor product, now called FontLab Studio. Since the early 2000s, FontLab Studio has been the dominant software tool for commercial/retail digital font development. This is partly because the...
SigMaker3 application.
The SING specification states that glyphlets are to travel with the document they are used in. That way documents are portable, leaving no danger of characters in the document that cannot be displayed. Because glyphlets are essentially OpenType fonts, standard font machinery can render them. The SING specification also describes an
XMLExtensible Markup Language is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards....
format that includes all the data necessary for reconstituting the glyphlet in binary form. A typical glyphlet might require one to two kilobytes to represent.
Security issues
Critical security update for
Windows VistaWindows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
KB969947 resolves several security issues that "could allow remote code execution if a user viewed content rendered in a specially crafted Embedded OpenType (EOT) font". Such fonts could be embedded in Web sites, including those that host user-provided content.
See also
- Uniscribe
Uniscribe is the Microsoft Windows set of services for rendering Unicode-encoded text, especially complex text layout. They are implemented in the DLL USP10.DLL. USP10.dll became available to the public with Windows 2000 and Internet Explorer 5.0...
(Windows multilingual text rendering engine)
- Windows Presentation Foundation
Developed by Microsoft, the Windows Presentation Foundation is a computer-software graphical subsystem for rendering user interfaces in Windows-based applications. WPF, previously known as "Avalon", was initially released as part of .NET Framework 3.0. Rather than relying on the older GDI...
(The first Windows API with near complete OpenType support)
- Apple Type Services for Unicode Imaging
The Apple Type Services for Unicode Imaging is the set of services for rendering Unicode-encoded text starting with Mac OS 8.5 and in Mac OS X.It replaced the WorldScript engine for legacy encodings....
(Macintosh multilingual text rendering engine)
- WorldScript
WorldScript was the multilingual text rendering engine for Apple Macintosh before Mac OS X was introduced.Starting with version 7.1, Apple unified the implementation of non-Roman script systems in a programming interface called WorldScript. WorldScript I was used for all one-byte character sets and...
(Old Macintosh multilingual text rendering engine)
- Pango
Pango is an LGPL licensed open source computing library used by software developers for laying out and rendering text in high quality, emphasising support for multilingual text...
(Open source multilingual text rendering engine)
- XeTeX
XeTeX is a TeX typesetting engine using Unicode and supporting modern font technologies such as OpenType or Apple Advanced Typography...
A free typesetting system based on a merger of TeXTeX is a typesetting system designed and mostly written by Donald Knuth and released in 1978. Within the typesetting system, its name is formatted as ....
with Unicode and Mac OS X font technologies.
- International Components for Unicode
International Components for Unicode is an open source project of mature C/C++ and Java libraries for Unicode support, software internationalization and software globalization. ICU is widely portable to many operating systems and environments. It gives applications the same results on all...
(Open source multilingual architecture with a font layout library)
- List of typographic features
- Embedded OpenType
Embedded OpenType fonts are a compact form of OpenType fonts designed by Microsoft for use as embedded fonts on web pages. These files usually use the extension ".eot"....
- Typography
Typography is the art and technique of arranging type in order to make language visible. The arrangement of type involves the selection of typefaces, point size, line length, leading , adjusting the spaces between groups of letters and adjusting the space between pairs of letters...
- Bitstream Panorama
Panorama is a line layout and text composition engine to render text in various worldwide languages made by Bitstream Inc.. Panorama uses Font Fusion as the base to support rendering of the text...
- FreeType
FreeType is a software library written in C that implements a font rasterization engine. It is used to render text on to bitmaps and provides support for other font-related operations.-Details:...
- WOFF (Web Open Font Format)
The Web Open Font Format is a font format for use in web pages. It was developed during 2009 and is in the process of being standardized as a recommendation by the World Wide Web Consortium Web Fonts Working Group....
, a webfont format that contains an OpenType font with metadata
External links