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Wikipedia

OpenType

January 29, 2023

OpenType is a format for scalable computer fonts. It was built on its predecessor TrueType, retaining TrueType's basic structure and adding many intricate data structures for prescribing typographic behavior. OpenType is a registered trademark of Microsoft Corporation.[4][5]

OpenType
Filename extensions.otf, .otc, .ttf, .ttc
Internet media type
  • font/otf
  • font/sfnt
  • application/font-sfnt (deprecated)
[1]
Type codeOTTO
Uniform Type Identifier (UTI)public.opentype-font
Developed byMicrosoft, Adobe Systems
Latest release
1.9[2]
8 December 2021; 13 months ago (2021-12-08)
Type of formatFont file
Extended fromTrueType, PostScript fonts
StandardISO/IEC 14496-22:2019[3]

The specification germinated at Microsoft, with Adobe Systems also contributing by the time of the public announcement in 1996.

Because of wide availability and typographic flexibility, including provisions for handling the diverse behaviors of all the world's writing systems, OpenType fonts are used commonly on major computer platforms.

History

OpenType's origins date to Microsoft's attempt to license Apple's advanced typography technology GX Typography in the early 1990s. Those negotiations failed, motivating Microsoft to forge ahead with its own technology, dubbed "TrueType Open" in 1994.[6] 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 TrueType and Adobe's Type 1 ("PostScript") 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 Standardization (ISO) within the MPEG group, which had previously (in 2003) adopted OpenType 1.4 by reference for MPEG-4.[5][7][8][9] 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, not to be confused with Web Open Font Format).[10] It is also sometimes referred to as "Open Font Format Specification" (OFFS).[5] The initial standard was technically equivalent to OpenType 1.4 specification, with appropriate language changes for ISO.[11] The second edition of the Open Font Format was published in 2009 (ISO/IEC 14496-22:2009) and was declared "technically equivalent" to the "OpenType font format specification".[12][13] Since then, the Open Font Format and the OpenType specification have continued to be maintained in sync. OFF is a free, publicly available standard.[14]

By 2001 hundreds of OpenType fonts were on the market. Adobe finished converting their entire font library to OpenType toward the end of 2002. As of early 2005, around 10,000 OpenType fonts had become available, with the Adobe library comprising about a third of the total. By 2006, every major font foundry and many minor ones were developing fonts in OpenType format.[citation needed]

Unicode Variation Sequences

Unicode version 3.2 (published in 2002) introduced variation selectors as an encoding mechanism to represent particular glyph forms for characters.[15] Unicode did not, however, specify how text-display implementations should support these sequences. In late 2007, variation sequences for the Adobe-Japan1 collection were registered in the Unicode Ideographic Database,[16] leading to a real need for an OpenType solution. This resulted in development of cmap subtable Format 14, which was introduced in OpenType version 1.5.[17]

Color fonts

Unicode version 6.0 introduced emoji encoded as characters into Unicode in October 2010.[18] Several companies quickly acted to add support for Unicode emoji in their products. Since Unicode emoji are handled as text, and since color is an essential aspect of the emoji experience, this led to a need to create mechanisms for displaying multicolor glyphs.

Apple, Google and Microsoft independently developed different color-font solutions for use in OS X/iOS, Android and Windows. OpenType / OFF already had support for monochrome bitmap glyph, and so Google proposed that OFF be extended to allow for color bitmaps. This was the approach being taken by Apple, though Apple declined to participate in extending the ISO standard. As a result, Apple added the 'sbix' table to their TrueType format in OS X 10.7,[19] while Google proposed addition of the CBDT and CBLC tables to OFF.

Microsoft adopted a different approach than color bitmaps. Noting existing practice on the Web of layering glyphs of different color on top of one another to create multi-colored elements such as icons, Microsoft proposed a new COLR table to map a glyph into a set of glyphs that are layered, and a CPAL table to define the colors.

Adobe and Mozilla proposed yet another approach: add a new 'SVG ' table that can contain multi-color glyphs represented using Scalable Vector Graphics.

The Adobe/Mozilla, Microsoft and Google proposals were all incorporated into the third edition of OFF (ISO/IEC 14496-22:2015).[20] The new tables

  • CBDT
  • CBLC
  • COLR
  • CPAL
  • SVG␠

were added to OpenType version 1.7.[17]

While Microsoft originally supported only the COLR/CPAL color format, support for all of the different color formats, including Apple's 'sbix' format, was added to Microsoft Windows in the Windows 10 Anniversary Update.[21] The 'sbix' table was subsequently added to OpenType in version 1.8.[17]

In OpenType 1.9, a second version of the COLR table was introduced that adds additional graphics capabilities.[17] The enhanced version was originally proposed by Google and developed jointly with Microsoft. The enhanced graphic capabilities include support for three types of gradients, affine transformations, compositing and blending modes, and ability to define re-usable components.[22] These enhancements give the COLR table all of the graphic capabilities of the 'SVG ' table that applications are expected to support except for stroking. It also adds compositing and blending modes, support for which is considered optional for the 'SVG ' table (as these are implemented in SVG as filter effects).[23] In addition, the enhancements to the COLR table are integrated with OpenType Font Variations, which is not possible with the 'SVG ' table. The enhanced COLR table is supported in the Chromium browser engine as of version 98.[24]

OpenType Collections

Since at least version 1.4, the OpenType specification had supported "TrueType Collections", a feature of the format that allows multiple fonts to be stored in a single file. Such a format is useful for distributing an entire typeface (font family) in just one file.

By combining related fonts into a single file, font tables that are identical can be shared, thereby allowing for more efficient storage. Also, individual fonts have a glyph-count limit of 65,535 glyphs, and a Collection file provides a "gap mode" mechanism for overcoming this limit in a single font file. (Each font within the collection still has the 65,535 limit, however.) A TrueType Collection file would typically have a file extension of ".ttc".

However, the specification only described collection files being used in conjunction with glyphs that are represented as TrueType outlines or as bitmaps. The potential existed to provide the same storage and glyph-count benefits to fonts that use CFF-format glyphs (.otf extension). But the specification did not explicitly allow for that.

In 2014, Adobe announced the creation of OpenType Collections (OTCs), a Collection font file that combines fonts that use CFF-format glyphs.[25] This provided significant storage benefits for CJK fonts that Adobe and Google were jointly developing. For example, the Noto fonts CJK OTC is ~10 MB smaller than the sum of the four separate OTFs of which it is composed.[26] The use of a Collection also allowed for combining a very large number of glyphs into a single file, as would be needed for a pan-CJK font.[27]

Explicit support for Collections with CFF-format glyphs was incorporated into the OpenType specification in version 1.8.[17] To reflect this more-inclusive applicability, the term "OpenType Collection" was adopted, superseding "TrueType Collection".

OpenType Font Variations

See also: Variable fonts

On September 14, 2016, Microsoft announced the release of OpenType version 1.8. This announcement was made together with Adobe, Apple, and Google at the ATypI conference in Warsaw.[28] OpenType version 1.8 introduced "OpenType Font Variations", which adds mechanisms that allow a single font to support many design variations.[29] Fonts that use these mechanisms are commonly referred to as "OpenType variable fonts".

OpenType Font Variations re-introduces techniques that were previously developed by Apple in TrueType GX, and by Adobe in Multiple Master fonts. The common idea of these formats is that a single font includes data to describe multiple variations of a glyph outline (sometimes referred to as "masters"), and that at text-display time, the font rasterizer is able to interpolate or "blend" these variations to derive a continuous range of additional outline variations.[30]

The concept of fully parametric fonts had been explored in a more general way by Donald E. Knuth in the METAFONT system, introduced in 1978.[31] That system and its successors were never widely adopted by professional type designers or commercial software systems.[32] TrueType GX and Multiple Master formats, OpenType Font Variations' direct predecessors, were introduced in the 1990s, but were not widely adopted, either. Adobe later abandoned support for the Multiple Master format.[33] This has led to questions as to whether a re-introduction of similar technology could succeed. By 2016, however, the industry landscape had changed in several respects. In particular, emergence of Web fonts and of mobile devices had created interest in responsive design and in seeking ways to deliver more type variants in a size-efficient format. Also, whereas the 1990s was an era of aggressive competition in font technology, often referred to as "the font wars",[34][35][36] OpenType Font Variations was developed in a collaborative manner involving several major vendors.[37]

Font Variations is integrated into OpenType 1.8 in a comprehensive manner, allowing most previously-existing capabilities to be used in combination with variations. In particular, variations are supported for both TrueType or CFF glyph outlines, for TrueType hinting, and also for the OpenType Layout mechanisms. The only parts of OpenType for which variations are not supported but might potentially be useful are the 'SVG ' table for color glyphs, and the MATH table for layout of mathematical formulas. The 'SVG ' table uses embedded XML documents, and no enhancement for variation of graphic elements within the SVG documents has been proposed. However, enhancement to the COLR table in OpenType 1.9 has provided a vector format for color glyphs with support for variations.[38]

OpenType 1.8 made use of tables originally defined by Apple for TrueType GX (the avar, cvar, fvar and gvar tables). It also introduced several new tables, including a new table for version 2 of the CFF format (CFF2), and other new tables or additions to existing tables to integrate variations into other parts of the font format (the HVAR, MVAR, STAT and VVAR tables; additions to the BASE, GDEF and name tables).[17]

Description

  •  

    TrueType outlines use quadratic Bézier curves.

  •  

    CFF outlines use cubic Bézier curves.

OpenType uses the general sfnt structure of a TrueType font, but it adds several smartfont options that enhance the font's typographic and language support capabilities.

The glyph 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 PostScript language Type 2 font format. However, the OpenType specification (pre-1.8) does not support the use of PostScript outlines in a TrueType Collection font file. After version 1.8, both formats are supported in the renamed "OpenType Collection".

For many purposes, such as layout, it doesn't matter what the outline data format is, but for some purposes, such as rasterisation, it is significant. The OpenType standard does not specify the outline data format: rather, it accommodates 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 character encoding (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, mark placement, and baseline specification.
  • Cross-platform font files, which can be used without modification on Mac OS, Microsoft Windows and Unix/Linux 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 Computer's "GX Typography"—now called Apple Advanced Typography (AAT)—and with the SIL's Graphite technology, OpenType is less flexible in typographic options, but superior in language-related options and support.[clarification needed] Nevertheless, OpenType has been adopted much more widely than AAT or Graphite, despite AAT being the older technology.

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 syntax. Second, Adobe's strategy of licensing at no charge the source code developed for its own font development, AFDKO (Adobe Font Development Kit for OpenType), allowed third-party font editing applications such as FontLab 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 Uniscribe) needs to provide a fair bit of knowledge about special language processing issues to handle certain languages (e.g. 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 layout if the application or operating system knows how to handle them.

Prior to supporting OpenType, Adobe promoted multiple master fonts and expert fonts for high-end typography. Multiple master fonts were essentially an earlier (and less flexible) version of OpenType variable fonts, but lacked the controls for alternate glyphs and languages provided by OpenType. Expert fonts were a workaround for alternate glyphs, provided instead as separate supplementary fonts, such that certain 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 alternate glyphs are referenced by their relationship to the default glyph or glyphs (i.e. under what circumstances that glyph should be used) for the particular Unicode codepoint(s).

OpenType support

Basic Roman support

OpenType support may be divided into several categories.[citation needed] Virtually all applications and most modern operating systems have basic Roman support and work with OpenType fonts just as well as other, older formats. Benefits beyond basic Roman support include extended language support through Unicode, support for complex writing scripts such as Arabic and the Indic languages, and advanced typographic support for Latin script languages such as English.

Amongst Microsoft's operating systems, OpenType TT fonts (.TTF) are backward compatible and therefore supported by all Microsoft Windows versions starting with Microsoft Windows 3.1. OpenType PS fonts (.OTF) are supported in all Windows versions starting with Microsoft Windows 2000; Adobe Type Manager is required to be installed on Microsoft Windows 95/98/NT/Me for basic Roman support (only) of OpenType PS fonts.

Extended language support

Extended language support via Unicode for both OpenType and TrueType is present in most applications for Microsoft Windows[citation needed] (including Microsoft Office Publisher, most Adobe 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 TextEdit, Pages and Keynote. It is also widely supported in free operating systems, such as Linux (e.g. in multiplatform applications like AbiWord, Gnumeric, Calligra Suite, Scribus, OpenOffice.org 3.2 and later versions,[39] etc.).

OpenType support for complex written scripts has so far mainly appeared in Microsoft applications in Microsoft Office, such as Microsoft Word and Microsoft Publisher. Adobe InDesign provides extensive OpenType capability in Japanese but does not directly support Middle Eastern or Indic scripts—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 InDesign, Adobe Photoshop and Adobe Illustrator. QuarkXPress 6.5 and below were not Unicode compliant. Hence text in these versions of QuarkXPress that contains anything other than WinANSI/MacRoman 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 CorelDRAW introduced support for OpenType typographic features in version X6. Mellel, 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.

As of 2009, popular word processors for Microsoft Windows did not support advanced OpenType typography features. Advanced typography features are implemented only in high-end desktop publishing software. The text engine from Windows Presentation Foundation, which is a managed code implementation of OpenType, is the first Microsoft Windows API to expose OpenType features to software developers, supporting both OpenType TrueType, and OpenType CFF (Compact Font Format) fonts. It supports advanced typographic features such as ligatures, old-style numerals, swash variants, fractions, superscript and subscript, small capitalization, glyph substitution, multiple baselines, contextual and stylistic alternate character forms, kerning, line-level justification, ruby characters etc.[40] WPF applications automatically gain support for advanced typography features. OpenType ligatures are accessible in Microsoft Office Word 2010.[41]

Windows 7 introduced DirectWrite, a hardware accelerated native DirectX API for text rendering with support for multi-format text, resolution-independent outline fonts, ClearType, advanced OpenType typography features, full Unicode text, layout and language support and low-level glyph rendering APIs.[42]

On Mac OS X, AAT-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 caps, old-style 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. Gradually, the OpenType typography support has improved on newer Mac OS X versions (e.g., Mac OS X 10.10 can handle much better long contextual glyph substitutions).

Bitstream Panorama, a line layout and text composition engine from Bitstream Inc., 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 software environments such as Linux, OpenType rendering is provided by the FreeType project, included in free implementations of the X Window System such as X.org. Complex text handling is provided either by pango (calling HarfBuzz) or Qt. The XeTeX and LuaTeX systems allow TeX documents to use OpenType fonts, along with most of their typographic features. Linux version of LibreOffice 4.1 and newer supports many OpenType typography features, because it began to use more sophisticated HarfBuzz text shaping library.[43]

OpenType Feature File

As a step in the creation of a font, OpenType font properties (other than the outline) can be defined using human-readable text saved in Adobe's OpenType Feature File format.[44][45] OpenType Feature Files typically have a name ending in a .fea extension. These files can be compiled into the binary font container (.ttf or .otf) using Adobe Font Development Kit for OpenType (AFDKO), FontLab, FontForge, Glyphs, DTL OTMaster, RoboFont or FontTools.

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 Studio, AsiaFont Studio, and FontForge.

Operating system and application support for layout tags varies widely.

Script tags

Script tags identify the scripts (writing systems) represented in an OpenType font. Each tag corresponds to contiguous character code ranges in Unicode. A script tag can consist of 4 or fewer lowercase letters, such as arab for the Arabic alphabet, cyrl for the Cyrillic script and latn for the Latin alphabet. The math script tag, added by Microsoft for Cambria Math, has been added to the specification.[46][47]

Language system tags

Language system tags identify the language systems supported in an OpenType font. Examples include ARA for Arabic, ESP for Spanish, HYE for Armenian, etc. In general, the codes are not the same as ISO 639-2 codes.[48]

Feature tags

Main article: OpenType feature tag list

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 tags and axes in OpenType fonts
Baseline tag HorizAxis VertAxis
'hang' horizontal line from which the syllabograms seem to hang in the Tibetan script 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 baseline used by simple alphabetic scripts such as Latin, Cyrillic and Greek. The alphabetic baseline for characters rotated 90 degrees clockwise for vertical writing mode.

Math

A set of tables that mirrors TeX math font metrics relatively closely was added by Microsoft initially to Cambria Math for supporting their new math editing and rendering engine in Office 2007 and later.[49][50] This extension was added to the ISO standard (ISO/IEC CD 14496-22 3rd edition) in April 2014.[51] Additional (usage) details are available in the Unicode technical report 25[52] and technical note 28.[53] Some of the new technical features (not present in TeX), such as "cut-ins" (which allows kerning of subscripts and superscripts relative to their bases[54]) and stretch stacks[55] have been patented by Microsoft.[56][57][58] Windows 8 supports OpenType math outside MS Office applications via the RichEdit 8.0 component.[59]

Besides Microsoft products, XeTeX and LuaTeX also have some level of support for these tables; support is more limited in XeTeX because it uses the traditional TeX math rendering engine (thus it cannot fully use some of the new features in OpenType math that extend TeX), while LuaTeX takes a more flexible approach by changing some of the internals of TeX's math rendering; in the words of Ulrik Vieth (2009): "More precisely, while XeTeX only provides access to the OpenType parameters as additional \fontdimens, LuaTeX uses an internal data structure based on the combined set of OpenType and TeX parameters, making it possible to supply missing values which are not supported in either OpenType math fonts or traditional TeX math fonts."[55] In 2013, XeTeX also gained support for cut-ins.[60]

The Gecko rendering engine used by the Firefox web browser also supports some OpenType math features in its MathML implementation.[61][62]

As of 2010, the set of fonts that supported OpenType math was fairly limited. Besides Cambria Math, three free fonts were available: Asana-Math, Neo Euler, and XITS.[63] More recently the Latin Modern and TeX Gyre fonts (an "LM-ization" of the standard PostScript fonts[64]) have also gained support for OpenType math.[65][66][67][68] As of 2014 the number of OpenType math fonts is still fairly limited.[69] A more up-to-date list is maintained on Mozilla's web site.[70]

Color

Emergence of Unicode emoji created a need for TrueType and OpenType formats to support color glyphs. Apple added a color extension in Mac OS X Lion (and also to iOS 4+). Fonts were extended with colored PNG images within the sbix table.[71][72][73] Google used a similar extension with embedded color bitmap images contained within a pair of tables, the CBDT and CBLC tables.[74] The Google version is implemented in FreeType 2.5.[75]

In Windows 8.1 Microsoft also added color support to fonts, first implemented in the Segoe UI Emoji font.[72][76][77][78] Microsoft's implementation, however, relies entirely on vector graphics:[72][79] two new OpenType tables were added in Microsoft's implementation: the COLR table allows layered glyphs and the CPAL ("Color Palette") actually defines the colors for the layers. The multi-layer approach allows a backwards compatible implementation as well as varying the rendering depending on the color context surrounding the glyphs.[72] According to Adam Twardoch: "At TypeCon [2013], Greg Hitchcock clarified the envisioned roles of the palettes: first palette is used by default for "dark on light" color situations while second palette is intended for use in "light on dark" situations. Additional palettes should be selectable by the user."[75]

Mozilla and Adobe developed a different vector-based extension by adding embedded SVG documents (supporting color but also animations) into the SVG table. The SVG table also allowed for using color palettes defined in the CPAL table.[80] Support was first implemented in Firefox 26.[74]

Adobe, Mozilla, Google and Microsoft each submitted their color extensions for standardization thorough ISO/IEC 14496-22.[81] The new tables for each of these were then added into OpenType version 1.7.[82] Apple's sbix table was originally supported only in AAT fonts, but it was later added into OpenType version 1.8.[83] Microsoft Windows 10 Anniversary Update was the first OS to support all four color font extensions, and Microsoft Edge was the first browser to do so.[84][85]

In OpenType Version 1.8.3, the specification for the SVG table was revised to be more constrained, providing more clarity for implementations and better interoperability. Apple is supporting the revised specification in Safari 12, iOS12 and macOS 10.14.[86] The implementation in Microsoft Windows also conforms to this revision.

SING gaiji solution

In 2005, Adobe shipped a new technology in their Creative Suite applications bundle that offers a solution for "gaiji" (外字, Japanese for "outside character"). 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 East Asian 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 Areas (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)[87][88] 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 TrueType 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's 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 XML 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.

Language-specific variation

 
Variations in Cyrillic cursive. Letters in same row have the same code point.

Serbian/Macedonian Cyrillic may use some language-specific glyphs. These are only preferred and are not strictly mandated. In Unicode, these are encoded in a single code point and OpenType allows showing these language-specific glyphs using language tags[89] and the locl feature.[90]

See also

References

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External links

  • The OpenType Specification (Microsoft)
  • Adobe – Fonts: OpenType
  • Wakamai Fondue: website for checking the features of OpenType fonts

January 29, 2023
opentype, format, scalable, computer, fonts, built, predecessor, truetype, retaining, truetype, basic, structure, adding, many, intricate, data, structures, prescribing, typographic, behavior, registered, trademark, microsoft, corporation, filename, extensions. OpenType is a format for scalable computer fonts It was built on its predecessor TrueType retaining TrueType s basic structure and adding many intricate data structures for prescribing typographic behavior OpenType is a registered trademark of Microsoft Corporation 4 5 OpenTypeFilename extensions otf otc ttf ttcInternet media typefont otffont sfntapplication font sfnt deprecated 1 Type codeOTTOUniform Type Identifier UTI public opentype fontDeveloped byMicrosoft Adobe SystemsLatest release1 9 2 8 December 2021 13 months ago 2021 12 08 Type of formatFont fileExtended fromTrueType PostScript fontsStandardISO IEC 14496 22 2019 3 The specification germinated at Microsoft with Adobe Systems also contributing by the time of the public announcement in 1996 Because of wide availability and typographic flexibility including provisions for handling the diverse behaviors of all the world s writing systems OpenType fonts are used commonly on major computer platforms Contents 1 History 1 1 Open Font Format 1 2 Unicode Variation Sequences 1 3 Color fonts 1 4 OpenType Collections 1 5 OpenType Font Variations 2 Description 3 Comparison to other formats 4 OpenType support 4 1 Basic Roman support 4 2 Extended language support 4 3 Advanced typography 5 OpenType Feature File 6 Layout tags 6 1 Script tags 6 2 Language system tags 6 3 Feature tags 6 4 Baseline tags 6 5 Math 6 6 Color 7 SING gaiji solution 8 Language specific variation 9 See also 10 References 11 External linksHistory EditOpenType s origins date to Microsoft s attempt to license Apple s advanced typography technology GX Typography in the early 1990s Those negotiations failed motivating Microsoft to forge ahead with its own technology dubbed TrueType Open in 1994 6 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 TrueType and Adobe s Type 1 PostScript 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 Edit 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 Standardization ISO within the MPEG group which had previously in 2003 adopted OpenType 1 4 by reference for MPEG 4 5 7 8 9 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 not to be confused with Web Open Font Format 10 It is also sometimes referred to as Open Font Format Specification OFFS 5 The initial standard was technically equivalent to OpenType 1 4 specification with appropriate language changes for ISO 11 The second edition of the Open Font Format was published in 2009 ISO IEC 14496 22 2009 and was declared technically equivalent to the OpenType font format specification 12 13 Since then the Open Font Format and the OpenType specification have continued to be maintained in sync OFF is a free publicly available standard 14 By 2001 hundreds of OpenType fonts were on the market Adobe finished converting their entire font library to OpenType toward the end of 2002 As of early 2005 update around 10 000 OpenType fonts had become available with the Adobe library comprising about a third of the total By 2006 every major font foundry and many minor ones were developing fonts in OpenType format citation needed Unicode Variation Sequences Edit Unicode version 3 2 published in 2002 introduced variation selectors as an encoding mechanism to represent particular glyph forms for characters 15 Unicode did not however specify how text display implementations should support these sequences In late 2007 variation sequences for the Adobe Japan1 collection were registered in the Unicode Ideographic Database 16 leading to a real need for an OpenType solution This resulted in development of cmap subtable Format 14 which was introduced in OpenType version 1 5 17 Color fonts Edit Unicode version 6 0 introduced emoji encoded as characters into Unicode in October 2010 18 Several companies quickly acted to add support for Unicode emoji in their products Since Unicode emoji are handled as text and since color is an essential aspect of the emoji experience this led to a need to create mechanisms for displaying multicolor glyphs Apple Google and Microsoft independently developed different color font solutions for use in OS X iOS Android and Windows OpenType OFF already had support for monochrome bitmap glyph and so Google proposed that OFF be extended to allow for color bitmaps This was the approach being taken by Apple though Apple declined to participate in extending the ISO standard As a result Apple added the sbix table to their TrueType format in OS X 10 7 19 while Google proposed addition of the CBDT and CBLC tables to OFF Microsoft adopted a different approach than color bitmaps Noting existing practice on the Web of layering glyphs of different color on top of one another to create multi colored elements such as icons Microsoft proposed a new COLR table to map a glyph into a set of glyphs that are layered and a CPAL table to define the colors Adobe and Mozilla proposed yet another approach add a new SVG table that can contain multi color glyphs represented using Scalable Vector Graphics The Adobe Mozilla Microsoft and Google proposals were all incorporated into the third edition of OFF ISO IEC 14496 22 2015 20 The new tablesCBDTCBLCCOLRCPALSVG were added to OpenType version 1 7 17 While Microsoft originally supported only the COLR CPAL color format support for all of the different color formats including Apple s sbix format was added to Microsoft Windows in the Windows 10 Anniversary Update 21 The sbix table was subsequently added to OpenType in version 1 8 17 In OpenType 1 9 a second version of the COLR table was introduced that adds additional graphics capabilities 17 The enhanced version was originally proposed by Google and developed jointly with Microsoft The enhanced graphic capabilities include support for three types of gradients affine transformations compositing and blending modes and ability to define re usable components 22 These enhancements give the COLR table all of the graphic capabilities of the SVG table that applications are expected to support except for stroking It also adds compositing and blending modes support for which is considered optional for the SVG table as these are implemented in SVG as filter effects 23 In addition the enhancements to the COLR table are integrated with OpenType Font Variations which is not possible with the SVG table The enhanced COLR table is supported in the Chromium browser engine as of version 98 24 OpenType Collections Edit Since at least version 1 4 the OpenType specification had supported TrueType Collections a feature of the format that allows multiple fonts to be stored in a single file Such a format is useful for distributing an entire typeface font family in just one file By combining related fonts into a single file font tables that are identical can be shared thereby allowing for more efficient storage Also individual fonts have a glyph count limit of 65 535 glyphs and a Collection file provides a gap mode mechanism for overcoming this limit in a single font file Each font within the collection still has the 65 535 limit however A TrueType Collection file would typically have a file extension of ttc However the specification only described collection files being used in conjunction with glyphs that are represented as TrueType outlines or as bitmaps The potential existed to provide the same storage and glyph count benefits to fonts that use CFF format glyphs otf extension But the specification did not explicitly allow for that In 2014 Adobe announced the creation of OpenType Collections OTCs a Collection font file that combines fonts that use CFF format glyphs 25 This provided significant storage benefits for CJK fonts that Adobe and Google were jointly developing For example the Noto fonts CJK OTC is 10 MB smaller than the sum of the four separate OTFs of which it is composed 26 The use of a Collection also allowed for combining a very large number of glyphs into a single file as would be needed for a pan CJK font 27 Explicit support for Collections with CFF format glyphs was incorporated into the OpenType specification in version 1 8 17 To reflect this more inclusive applicability the term OpenType Collection was adopted superseding TrueType Collection OpenType Font Variations Edit See also Variable fonts On September 14 2016 Microsoft announced the release of OpenType version 1 8 This announcement was made together with Adobe Apple and Google at the ATypI conference in Warsaw 28 OpenType version 1 8 introduced OpenType Font Variations which adds mechanisms that allow a single font to support many design variations 29 Fonts that use these mechanisms are commonly referred to as OpenType variable fonts OpenType Font Variations re introduces techniques that were previously developed by Apple in TrueType GX and by Adobe in Multiple Master fonts The common idea of these formats is that a single font includes data to describe multiple variations of a glyph outline sometimes referred to as masters and that at text display time the font rasterizer is able to interpolate or blend these variations to derive a continuous range of additional outline variations 30 The concept of fully parametric fonts had been explored in a more general way by Donald E Knuth in the METAFONT system introduced in 1978 31 That system and its successors were never widely adopted by professional type designers or commercial software systems 32 TrueType GX and Multiple Master formats OpenType Font Variations direct predecessors were introduced in the 1990s but were not widely adopted either Adobe later abandoned support for the Multiple Master format 33 This has led to questions as to whether a re introduction of similar technology could succeed By 2016 however the industry landscape had changed in several respects In particular emergence of Web fonts and of mobile devices had created interest in responsive design and in seeking ways to deliver more type variants in a size efficient format Also whereas the 1990s was an era of aggressive competition in font technology often referred to as the font wars 34 35 36 OpenType Font Variations was developed in a collaborative manner involving several major vendors 37 Font Variations is integrated into OpenType 1 8 in a comprehensive manner allowing most previously existing capabilities to be used in combination with variations In particular variations are supported for both TrueType or CFF glyph outlines for TrueType hinting and also for the OpenType Layout mechanisms The only parts of OpenType for which variations are not supported but might potentially be useful are the SVG table for color glyphs and the MATH table for layout of mathematical formulas The SVG table uses embedded XML documents and no enhancement for variation of graphic elements within the SVG documents has been proposed However enhancement to the COLR table in OpenType 1 9 has provided a vector format for color glyphs with support for variations 38 OpenType 1 8 made use of tables originally defined by Apple for TrueType GX the avar cvar fvar and gvar tables It also introduced several new tables including a new table for version 2 of the CFF format CFF2 and other new tables or additions to existing tables to integrate variations into other parts of the font format the HVAR MVAR STAT and VVAR tables additions to the BASE GDEF and name tables 17 Description Edit TrueType outlines use quadratic Bezier curves CFF outlines use cubic Bezier curves OpenType uses the general sfnt structure of a TrueType font but it adds several smartfont options that enhance the font s typographic and language support capabilities The glyph 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 PostScript language Type 2 font format However the OpenType specification pre 1 8 does not support the use of PostScript outlines in a TrueType Collection font file After version 1 8 both formats are supported in the renamed OpenType Collection For many purposes such as layout it doesn t matter what the outline data format is but for some purposes such as rasterisation it is significant The OpenType standard does not specify the outline data format rather it accommodates 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 character encoding 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 mark placement and baseline specification Cross platform font files which can be used without modification on Mac OS Microsoft Windows and Unix Linux 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 EditThis section does not cite any sources Please help improve this section by adding citations to reliable sources Unsourced material may be challenged and removed May 2013 Learn how and when to remove this template message Compared with Apple Computer s GX Typography now called Apple Advanced Typography AAT and with the SIL s Graphite technology OpenType is less flexible in typographic options but superior in language related options and support clarification needed Nevertheless OpenType has been adopted much more widely than AAT or Graphite despite AAT being the older technology 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 syntax Second Adobe s strategy of licensing at no charge the source code developed for its own font development AFDKO Adobe Font Development Kit for OpenType allowed third party font editing applications such as FontLab 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 Uniscribe needs to provide a fair bit of knowledge about special language processing issues to handle certain languages e g 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 layout if the application or operating system knows how to handle them Prior to supporting OpenType Adobe promoted multiple master fonts and expert fonts for high end typography Multiple master fonts were essentially an earlier and less flexible version of OpenType variable fonts but lacked the controls for alternate glyphs and languages provided by OpenType Expert fonts were a workaround for alternate glyphs provided instead as separate supplementary fonts such that certain 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 alternate glyphs are referenced by their relationship to the default glyph or glyphs i e under what circumstances that glyph should be used for the particular Unicode codepoint s OpenType support EditBasic Roman support Edit OpenType support may be divided into several categories citation needed Virtually all applications and most modern operating systems have basic Roman support and work with OpenType fonts just as well as other older formats Benefits beyond basic Roman support include extended language support through Unicode support for complex writing scripts such as Arabic and the Indic languages and advanced typographic support for Latin script languages such as English Amongst Microsoft s operating systems OpenType TT fonts TTF are backward compatible and therefore supported by all Microsoft Windows versions starting with Microsoft Windows 3 1 OpenType PS fonts OTF are supported in all Windows versions starting with Microsoft Windows 2000 Adobe Type Manager is required to be installed on Microsoft Windows 95 98 NT Me for basic Roman support only of OpenType PS fonts Extended language support Edit Extended language support via Unicode for both OpenType and TrueType is present in most applications for Microsoft Windows citation needed including Microsoft Office Publisher most Adobe 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 TextEdit Pages and Keynote It is also widely supported in free operating systems such as Linux e g in multiplatform applications like AbiWord Gnumeric Calligra Suite Scribus OpenOffice org 3 2 and later versions 39 etc OpenType support for complex written scripts has so far mainly appeared in Microsoft applications in Microsoft Office such as Microsoft Word and Microsoft Publisher Adobe InDesign provides extensive OpenType capability in Japanese but does not directly support Middle Eastern or Indic scripts 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 Edit Advanced typographic support for Latin script languages first appeared in Adobe applications such as Adobe InDesign Adobe Photoshop and Adobe Illustrator QuarkXPress 6 5 and below were not Unicode compliant Hence text in these versions of QuarkXPress that contains anything other than WinANSI MacRoman 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 CorelDRAW introduced support for OpenType typographic features in version X6 Mellel 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 As of 2009 update popular word processors for Microsoft Windows did not support advanced OpenType typography features Advanced typography features are implemented only in high end desktop publishing software The text engine from Windows Presentation Foundation which is a managed code implementation of OpenType is the first Microsoft Windows API to expose OpenType features to software developers supporting both OpenType TrueType and OpenType CFF Compact Font Format fonts It supports advanced typographic features such as ligatures old style numerals swash variants fractions superscript and subscript small capitalization glyph substitution multiple baselines contextual and stylistic alternate character forms kerning line level justification ruby characters etc 40 WPF applications automatically gain support for advanced typography features OpenType ligatures are accessible in Microsoft Office Word 2010 41 Windows 7 introduced DirectWrite a hardware accelerated native DirectX API for text rendering with support for multi format text resolution independent outline fonts ClearType advanced OpenType typography features full Unicode text layout and language support and low level glyph rendering APIs 42 On Mac OS X AAT 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 caps old style 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 Gradually the OpenType typography support has improved on newer Mac OS X versions e g Mac OS X 10 10 can handle much better long contextual glyph substitutions Bitstream Panorama a line layout and text composition engine from Bitstream Inc 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 software environments such as Linux OpenType rendering is provided by the FreeType project included in free implementations of the X Window System such as X org Complex text handling is provided either by pango calling HarfBuzz or Qt The XeTeX and LuaTeX systems allow TeX documents to use OpenType fonts along with most of their typographic features Linux version of LibreOffice 4 1 and newer supports many OpenType typography features because it began to use more sophisticated HarfBuzz text shaping library 43 OpenType Feature File EditAs a step in the creation of a font OpenType font properties other than the outline can be defined using human readable text saved in Adobe s OpenType Feature File format 44 45 OpenType Feature Files typically have a name ending in a fea extension These files can be compiled into the binary font container ttf or otf using Adobe Font Development Kit for OpenType AFDKO FontLab FontForge Glyphs DTL OTMaster RoboFont or FontTools Layout tags EditOpenType 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 Studio AsiaFont Studio and FontForge Operating system and application support for layout tags varies widely Script tags Edit Script tags identify the scripts writing systems represented in an OpenType font Each tag corresponds to contiguous character code ranges in Unicode A script tag can consist of 4 or fewer lowercase letters such as arab for the Arabic alphabet cyrl for the Cyrillic script and latn for the Latin alphabet The math script tag added by Microsoft for Cambria Math has been added to the specification 46 47 Language system tags Edit Language system tags identify the language systems supported in an OpenType font Examples include ARA for Arabic ESP for Spanish HYE for Armenian etc In general the codes are not the same as ISO 639 2 codes 48 Feature tags Edit Main article OpenType feature tag list A list of OpenType features with expanded descriptions is given list of typographic features Baseline tags Edit 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 tags and axes in OpenType fonts Baseline tag HorizAxis VertAxis hang horizontal line from which the syllabograms seem to hang in the Tibetan script 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 baseline used by simple alphabetic scripts such as Latin Cyrillic and Greek The alphabetic baseline for characters rotated 90 degrees clockwise for vertical writing mode Math Edit A set of tables that mirrors TeX math font metrics relatively closely was added by Microsoft initially to Cambria Math for supporting their new math editing and rendering engine in Office 2007 and later 49 50 This extension was added to the ISO standard ISO IEC CD 14496 22 3rd edition in April 2014 51 Additional usage details are available in the Unicode technical report 25 52 and technical note 28 53 Some of the new technical features not present in TeX such as cut ins which allows kerning of subscripts and superscripts relative to their bases 54 and stretch stacks 55 have been patented by Microsoft 56 57 58 Windows 8 supports OpenType math outside MS Office applications via the RichEdit 8 0 component 59 Besides Microsoft products XeTeX and LuaTeX also have some level of support for these tables support is more limited in XeTeX because it uses the traditional TeX math rendering engine thus it cannot fully use some of the new features in OpenType math that extend TeX while LuaTeX takes a more flexible approach by changing some of the internals of TeX s math rendering in the words of Ulrik Vieth 2009 More precisely while XeTeX only provides access to the OpenType parameters as additional fontdimens LuaTeX uses an internal data structure based on the combined set of OpenType and TeX parameters making it possible to supply missing values which are not supported in either OpenType math fonts or traditional TeX math fonts 55 In 2013 XeTeX also gained support for cut ins 60 The Gecko rendering engine used by the Firefox web browser also supports some OpenType math features in its MathML implementation 61 62 As of 2010 update the set of fonts that supported OpenType math was fairly limited Besides Cambria Math three free fonts were available Asana Math Neo Euler and XITS 63 More recently the Latin Modern and TeX Gyre fonts an LM ization of the standard PostScript fonts 64 have also gained support for OpenType math 65 66 67 68 As of 2014 update the number of OpenType math fonts is still fairly limited 69 A more up to date list is maintained on Mozilla s web site 70 Color Edit Emergence of Unicode emoji created a need for TrueType and OpenType formats to support color glyphs Apple added a color extension in Mac OS X Lion and also to iOS 4 Fonts were extended with colored PNG images within the sbix table 71 72 73 Google used a similar extension with embedded color bitmap images contained within a pair of tables the CBDT and CBLC tables 74 The Google version is implemented in FreeType 2 5 75 In Windows 8 1 Microsoft also added color support to fonts first implemented in the Segoe UI Emoji font 72 76 77 78 Microsoft s implementation however relies entirely on vector graphics 72 79 two new OpenType tables were added in Microsoft s implementation the COLR table allows layered glyphs and the CPAL Color Palette actually defines the colors for the layers The multi layer approach allows a backwards compatible implementation as well as varying the rendering depending on the color context surrounding the glyphs 72 According to Adam Twardoch At TypeCon 2013 Greg Hitchcock clarified the envisioned roles of the palettes first palette is used by default for dark on light color situations while second palette is intended for use in light on dark situations Additional palettes should be selectable by the user 75 Mozilla and Adobe developed a different vector based extension by adding embedded SVG documents supporting color but also animations into the SVG table The SVG table also allowed for using color palettes defined in the CPAL table 80 Support was first implemented in Firefox 26 74 Adobe Mozilla Google and Microsoft each submitted their color extensions for standardization thorough ISO IEC 14496 22 81 The new tables for each of these were then added into OpenType version 1 7 82 Apple s sbix table was originally supported only in AAT fonts but it was later added into OpenType version 1 8 83 Microsoft Windows 10 Anniversary Update was the first OS to support all four color font extensions and Microsoft Edge was the first browser to do so 84 85 In OpenType Version 1 8 3 the specification for the SVG table was revised to be more constrained providing more clarity for implementations and better interoperability Apple is supporting the revised specification in Safari 12 iOS12 and macOS 10 14 86 The implementation in Microsoft Windows also conforms to this revision SING gaiji solution EditIn 2005 Adobe shipped a new technology in their Creative Suite applications bundle that offers a solution for gaiji 外字 Japanese for outside character 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 East Asian 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 Areas 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 87 88 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 TrueType 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 s 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 XML 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 Language specific variation Edit Variations in Cyrillic cursive Letters in same row have the same code point Serbian Macedonian Cyrillic may use some language specific glyphs These are only preferred and are not strictly mandated In Unicode these are encoded in a single code point and OpenType allows showing these language specific glyphs using language tags 89 and the locl feature 90 See also EditUniscribe Windows multilingual text rendering engine Windows Presentation Foundation the first Windows API with near complete OpenType support Apple Type Services for Unicode Imaging Macintosh multilingual text rendering engine WorldScript old Macintosh multilingual text rendering engine Pango open source multilingual text rendering engine XeTeX a free typesetting system based on a merger of TeX with Unicode and Mac OS X font technologies List of typographic features Embedded OpenType Typography Bitstream Panorama FreeType WOFF Web Open Font Format a webfont format that contains an OpenType font with metadataReferences Edit Media Types IANA 2017 10 12 Retrieved 2017 10 17 OpenType specification Retrieved 2021 12 10 ISO IEC 14496 22 2019 Information technology Coding of audio visual objects Part 22 Open Font Format www iso org Retrieved 2015 12 13 US Registered Trademark Number 2217574 uspto gov January 12 1999 Retrieved September 30 2014 dead link a b c ISO IEC JTC 1 SC 29 WG 11 July 2008 ISO IEC 14496 22 Open Font Format chiariglione org Archived from the original on 2010 04 30 Retrieved 2020 02 21 Suitcase Type Foundry Information Guide PDF Archived from the original PDF on November 18 2006 ISO To Adopt OpenType File Format as Font Standard For MPEG 4 Adobe Systems Incorporated 2005 08 15 Archived from the original on 2011 06 05 Retrieved 2010 01 28 Referencing Explanatory Report to accompany FPDAM FDAM Submission of ISO IEC 14496 11 Amd 2 Referenced Specification The OpenType font format specification version 1 4 July 2003 Archived from the original DOC on 2014 05 12 Retrieved 2010 01 28 Combined CD Registration and CD Consideration Ballot on ISO IEC CD 14496 22 Information technology Coding of audio visual objects Part 22 Open Font Format SC 29 WG 11 N 7485 2005 09 01 Archived from the original DOC on 2014 05 12 Retrieved 2010 01 28 ISO IEC 14496 22 2007 Information technology Coding of audio visual objects Part 22 Open Font Format ISO 2009 07 31 Retrieved 2009 11 11 ISO 2007 03 15 ISO IEC 14496 22 First edition 2007 03 15 Information technology Coding of audio visual objects Part 22 Open Font Format ZIP Retrieved 2010 01 28 ISO IEC 14496 22 2009 Information technology Coding of audio visual objects Part 22 Open Font Format ISO 2009 07 31 Retrieved 2010 01 28 ISO 2009 08 15 ISO IEC 14496 22 Second edition 2009 08 15 Information technology Coding of audio visual objects Part 22 Open Font Format ZIP Retrieved 2010 01 28 Publicly Available Standards Standards iso org Retrieved 2009 11 11 Unicode Standard Annex 28 Unicode 3 2 www unicode org 2002 03 27 Retrieved 2017 04 22 Ideographic Variation Database www unicode org Retrieved 2017 04 22 a b c d e f OpenType specification change log www microsoft com Retrieved 2021 12 10 Unicode 6 0 0 www unicode org 2010 10 11 Retrieved April 22 2017 The sbix table developer apple com Retrieved April 22 2017 ISO IEC 14496 22 2015 Information technology Coding of audio visual objects Part 22 Open Font Format October 2015 Retrieved 2017 04 22 What s new in DirectWrite msdn microsoft com Retrieved 2017 04 22 COLR Color Table Retrieved 2021 12 10 SVG The SVG Scalable Vector Graphics Table Retrieved 2021 12 10 Feature COLRv1 Color Gradient Vector Fonts Retrieved 2021 12 10 Introducing amp Building OpenType Collections OTCs Blogs adobe com 2014 01 27 Retrieved 2017 01 19 Noto Sans CJK Google Noto Fonts Google com Retrieved 2017 01 19 Google and Adobe s pan CJK open font Lwn net Retrieved 2017 01 19 Archived at Ghostarchive and the Wayback Machine Special OpenType Session YouTube 2016 09 14 Retrieved 2017 04 22 John Hudson Introducing OpenType Variable Fonts Retrieved 2017 04 22 OpenType Font Variations Overview www microsoft com Retrieved 2017 04 22 Knuth Donald E Mathematical typography Bull Amer Math Soc N S 1 1979 no 2 337 372 https projecteuclid org euclid bams 1183544082 CSTUG Charles University Prague March 1996 Questions and Answers with Prof Donald E Knuth reproduced in TUGboat 17 4 1996 355 67 Citation is from page 361 Available online at http www tug org TUGboat Articles tb17 4 tb53knuc pdf Tamye Riggs 2014 07 30 The Adobe Originals Silver Anniversary Story How the Originals endured in an ever changing industry Retrieved 2017 04 22 Shimada James 2006 12 06 The Font Wars PDF Retrieved 2021 12 14 Adobe Inc Britannica Font Wars Retrieved 2022 04 10 Cringely Robert X 1996 Font Wars Accidental Empires Revised and updated ed Penguin Books pp 209 229 ISBN 0 14 025826 4 David Lemon 2017 01 27 The Font Wars Retrieved 2017 04 22 COLR table and OpenType Font Variations Retrieved 2021 12 13 OpenOffice Supports OpenType Fonts Retrieved 2011 02 03 Sysmalainen Julia Some Open Thoughts About OpenType Alphabettes Retrieved 15 May 2016 How to Enable OpenType Ligatures in Word 2010 Orzeszek org Retrieved 2009 11 11 Windows 7 Developer s Guide Code msdn microsoft com Retrieved 2009 11 11 LibreOffice 4 1 ReleaseNotes Retrieved 2015 04 15 Christopher Slye OpenType feature files ATypI 2006 slides OpenType Feature File Specification Retrieved 2019 03 20 Script tags OpenType Layout tag registry 2008 01 29 Retrieved 2009 11 02 International Organization for Standardization and International Electrotechnical Commission 2009 08 15 ISO IEC 14496 22 2009 E Information technology Coding of audio visual objects Part 22 Open Font Format 2nd ed pp 286 section 6 4 1 Retrieved 2009 11 02 consent to non chargeable online licence agreement required to download specification OpenType Layout tag registry Microsoft com 2017 01 05 Retrieved 2017 01 19 MurrayS3 2006 11 14 LineServices Murray Sargent Math in Office Blogs msdn com Retrieved 2017 01 19 Three Typefaces for Mathematics PDF Ultrasparky org Retrieved 2017 01 19 MurrayS3 2014 04 27 OpenType Math Tables Murray Sargent Math in Office Blogs msdn com Retrieved 2017 01 19 Unicode Technical Report 25 UNICODE SUPPORT FOR MATHEMATICS PDF Unicode org Retrieved 2017 01 19 UTN 28 Nearly Plain Text Encoding of Mathematics Unicode org 2016 11 16 Retrieved 2017 01 19 MurrayS3 2010 01 11 Special Capabilities of a Math Font Murray Sargent Math in Office Blogs msdn com Retrieved 2017 01 19 a b https www tug org TUGboat tb30 1 tb94vieth pdf also at http www ntg nl maps 38 03 pdf Patent US7492366 Method and system of character placement in opentype fonts Google Patents Google com 2008 03 03 Retrieved 2017 01 19 Patent US7242404 Enlargement of font characters Google Patents Google com 2007 02 16 Retrieved 2017 01 19 Patent US7453463 Enlargement of font characters Google Patents Google com Retrieved 2017 01 19 MurrayS3 2012 03 03 RichEdit 8 0 Preview Murray Sargent Math in Office Blogs msdn com Retrieved 2017 01 19 Preining Norbert 2013 06 19 TeX Live 2013 released Preining info Retrieved 2017 01 19 OpenType MATH Fonts Fred wang github io Retrieved 2017 01 19 MathML Open Type MATH Table MozillaWiki Wiki mozilla org 2015 12 27 Retrieved 2017 01 19 Experiences typesetting OpenType math with LuaLaTEX and XeLaTEX PDF Tug org Retrieved 2017 01 19 Jerzy B Ludwichowski The New Font Project TEX Gyre PDF Tug org Retrieved 2017 01 19 The Latin Modern Math LM Math font GUST Gust org pl in Polish Retrieved 2017 01 19 Package lm math CTAN Retrieved 2017 01 19 UK TUG 2012 TeX Gyre Math report on Vimeo Vimeo com 2012 10 22 Retrieved 2017 01 19 tex archive fonts tex gyre math CTAN 2016 05 19 Retrieved 2017 01 19 Progress of the TEX Gyre Math Font Project PDF Gust org Retrieved 2017 01 19 Fonts for Mozilla s MathML engine Mozilla MDN Developer mozilla org 2016 12 01 Retrieved 2017 01 19 Apple Color Emoji Typographica Typographica org 2014 06 20 Retrieved 2017 01 19 a b c d Color Emoji in Windows 8 1 The Future of Color Fonts Opentype info 3 July 2013 Archived from the original on 2014 07 10 Retrieved 2017 01 19 Apple Inc Extended Bitmaps Developer apple com Retrieved 2017 01 19 a b Roel Nieskens Colorful typography on the web get ready for multicolor fonts Pixelambacht Pixelambacht nl Retrieved 2017 01 19 a b FontLab Blog Color fonts Overview of the proposals for color extensions of the OpenType font format FontLab Blog Blog fontlab com 2013 09 19 Retrieved 2017 01 19 Script and Font Support in Windows Msdn microsoft com Archived from the original on 2013 01 10 Retrieved 2017 01 19 Petzold Book Blog Multicolor Font Characters in Windows 8 1 Charlespetzold com Retrieved 2017 01 19 Innovations in High Performance 2D Graphics with DirectX Build 2013 Channel 9 Channel9 msdn com 2013 06 25 Retrieved 2017 01 19 How to enter and use Emoji on Windows 8 1 Scott Hanselman Hanselman com Retrieved 2017 01 19 SVG The SVG Scalable Vector Graphics table docs microsoft com 2018 08 21 Retrieved 2018 09 14 Chromatic fonts are coming Lwn net Retrieved 2017 01 19 OpenType Version 1 7 docs microsoft com 2015 03 27 Retrieved 2018 09 14 OpenType Version 1 8 docs microsoft com 2016 09 14 Retrieved 2018 09 14 What s new in DirectWrite Retrieved 2018 09 14 Using color fonts for beautiful text and icons blogs microsoft com 2017 06 06 Retrieved 2018 09 14 What s New in Safari developer apple com Retrieved 2018 09 14 Adobe Glyphlet Development Kit GDK for SING Gaiji Architecture Adobe com Archived from the original on June 27 2008 Retrieved 2009 11 11 DeLaHunt Jim September 2004 SING Adobe s New Gaiji Architecture PDF 26th Internationalization and Unicode Conference Archived from the original PDF on 2015 01 23 Retrieved 16 July 2009 Language system tags OpenType 1 9 Typography learn microsoft com Registered features k o OpenType 1 9 Typography learn microsoft com External links EditThe OpenType Specification Microsoft Adobe Fonts OpenType Wakamai Fondue website for checking the features of OpenType fonts Retrieved from https en wikipedia org w index php title OpenType amp oldid 1134947380 Math, wikipedia, wiki, book, books, library,

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