OpenType is a concept for fonts originally developed by Microsoft and later developed jointly with Adobe , with a specially developed font format. It was released in 1996, and from 2000 onwards a larger number of OpenType fonts were launched.
Comparison with TrueType and PostScript
The OpenType format overcomes the major limitations of the widely used TrueType and Type 1 PostScript font formats :
- OpenType fonts are always in the form of a single font file ( Font ) before - as opposed to Type 1 fonts, where a single font style can be stored in up to five files, or fonts for the classic Mac OS, where font information can also be accommodated in the resource fork of the font files.
- Character class based kerning
- Characters that are to be treated in the same way (e.g. a, ä, á, à, å, etc.) are grouped in terms of their thickness and kerning pairs. This results in easier maintenance and savings in storage space requirements.
- Typographic skills
- In OpenType fonts, special typographic expressions can be mapped for a font, such as B. language-specific ligatures or dynamic character combinations. A font can also contain several character forms for individual characters. This is implemented using the so-called OpenType functions .
- Digital signature
- By applying a digital signature, a font manufacturer (foundry) can make the authenticity and integrity of a font file verifiable. This is especially important in the professional environment for legally correct licensing of fonts.
- Better Unicode support
- Like TrueType, OpenType also supports the addressing of the individual characters of a font using the Unicode tables; this overcomes the limit of 256 addressable characters per font that applies to traditional PostScript fonts.
OpenType fonts come in two flavors :
- TrueType-flavored OpenType (file extension .ttf) and
- PostScript-flavored OpenType (file extension .otf).
The characteristic relates to the type of storage of the data for the font curves, which are either embedded in the OpenType font in TrueType format (square splines ) or in PostScript CFF format ( compact font format , cubic splines). TrueType-flavored OpenType fonts also allow multiple codes to be assigned to the same glyph , e.g. B. as A (U + 0041), Alpha (U + 0391) and Cyrillic A (U + 0491).
The properties specific to OpenType are implemented generically using tables that are also built into the font.
Even if full support of OpenType functions has not yet been found on any platform, the fonts generally work at least as Unicode fonts, which can contain a character set of a maximum of 65536 glyphs, like newer versions of TrueType and Postscript (CFF format ). The use of the OpenType functions is usually made possible by suitable application programs (e.g. desktop publishing programs).
In the course of the migration of the font portfolio from the TrueType and PostScript formats to OpenType, the most important font manufacturers have not only implemented OpenType functions, but also, if necessary, previously managed fonts that belonged together (e.g. a version with small caps , old style figures or foreign language fonts) integrated into the associated OpenType font. In order to identify the differences in the character range of the various OpenType fonts, the font manufacturers have defined minimum character set ranges and expressed them with abbreviations in the name of the font. There is a standard character set scope ( OpenType Std ), a character set extension suitable for professional (typographical) use ( OpenType Pro ) and the character set designed for international communication ( OpenType Com ). These are marketed differently depending on the manufacturer.
While the examples are only typographical variants, there are many situations in which the use of a so-called smart font technique, as made possible by the OpenType format, is essential to create texts. Almost all writing systems derived from the Brahmi script such as B. Devanagari , Tibetan , Khmer and Tamil know complex rules for the use of positional letter forms and ligatures. Urdu can be written word by word from top right to bottom left using connected letters. The correct placement of diacritical marks and their theoretically unlimited stacking above and below letters is also made possible with OpenType. Last but not least, the technical possibilities of the OpenType format give the font developer a significantly expanded scope for design.
Common word processing and desktop publishing software supports OpenType options to a varying extent. Microsoft Office particularly supports the functions for so-called complex writing systems, bidirectional writing, and for the Latin script, at least the correct placement of diacritics . In addition, professional programs from Adobe, the program offers QuarkXPress 7, AbiWord and the Classical Text Editor replacements of characters as in the above examples under Windows and Mac OS X . The programs of the Adobe Creative Suite (Photoshop, Illustrator, InDesign) allow the use of OpenType functions at least since version CS3. They can be found in the palette menus for the font properties. Automatic replacement of ligatures and use of positional forms (variants for letters in the word or at the end) can also be assigned there. As of version 1.5.3, Scribus supports over 500 language-writing system combinations with OpenType.
OpenType is a registered trademark of Microsoft, but the technology can be transferred to other operating systems without restriction. Apple's Mac OS X supports PostScript and TrueType as well as OpenType fonts, and the easily portable open source project FreeType gives developers the opportunity to have full access to the OpenType functions of fonts and to integrate them into their programs. Desktop publishing programs from Adobe and QuarkXPress as well as Linux applications are increasingly benefiting from this . Furthermore, OpenType support can be integrated into applications with the program libraries ICU (International Components for Unicode), Qt and Pango , a by-product of GTK and GNOME .
Other smartfont techniques
In addition to OpenType, there are two other writing techniques that are designed for similar extended typographical possibilities. What they have in common is that, in addition to tables, they also use real programs, and that no convenient tools for font developers exist for any of them. Their support from application software is currently much less than that for OpenType.
- AAT ( Apple Advanced Typography ), the oldest smart font technology, is superior to OpenType in terms of typographical possibilities. However, OpenType is much more versatile. For copyright reasons, AAT may not simply be transferred to other platforms.
- Graphite , an open source project by SIL , was developed for the representation of minority languages. For characters that have not yet been standardized in Unicode, it is not uncommon to rely on the so-called Private Use Area (U + E000 - U + F8FF) as an interim solution. The characters encoded there are classified as letters in Unicode ( Lo = Letter, other ). Unlike OpenType, Graphite (like AAT) allows PUA characters to be treated differently, for example as diacritics. Worldpad, a simple text editor , is availablefor Graphite. SILA, a graphite-enhanced Mozilla browser, is in progress; very early versions can be tested. OpenOffice.org (since version 3.2) and LibreOffice provide Graphite support. Graphite is supported by UNESCO .
List of OpenType fonts with extensive SmartFont usage
- Minion Pro , designed by Adobe as a prime example of OpenType, OTF file
- Linux Libertine , OpenSource, OTF and TTF files
- Andika , Charis SIL , Doulos SIL , Gentium Plus and other fonts from SIL International under the SIL Open Font License
- Datalegreya , font freely available under the SIL Open Font License for the combined display of text and values
- Bahnschrift , model example for OpenType designed by Microsoft for Windows 10 - based on the German DIN font (according to DIN 1451), OTF file
- ↑ See the font overview on the download page . The third column from the right shows the use of OpenType technologies; for other Smartfont techniques see the column before and after.
- ↑ Railway font family. Microsoft, March 26, 2019, accessed January 15, 2020 .
- Jacques André: Caractères numériques: introduction. In: Cahiers GUTenberg. Vol. 26, May 1997, ISSN 1257-2217 , pp. 5-44, (in French).
- Yannis Haralambous: Fonts & encodings. From Unicode to advanced typography and everything in between. Translated by P. Scott Horne. O'Reilly, Beijing et al. 2007, ISBN 978-0-596-10242-5 (in English).
- Peter Karow: Digital Fonts. Presentation and formats. 2nd improved edition. Springer, Berlin et al. 1992, ISBN 3-540-54917-X .
- Mai-Linh Thi Truong, Jürgen Siebert, Erik Spiekermann (Eds.): FontBook. Digital Typeface Compendium (= FontBook 4). 4th revised and expanded edition. FSI FontShop International, Berlin 2006, ISBN 3-930023-04-0 (in English).
- OpenType at Microsoft (English)
- OpenType at Adobe (English)
- OpenType specification ISO / IEC 14496-22: 2015 (English)
- Graphite in SIL (English)
- SILA project (English)
- OpenGraphite Linux Porting Project (English)
- OpenType at Fraktur.biz (German)