TrueType
Encyclopedia
TrueType 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
. TrueType has become the most common format for fonts on both the Mac OS
and Microsoft Windows
operating systems.
The primary strength of TrueType was originally that it offered font
developers a high degree of control over precisely how their fonts are displayed, right down to particular pixel
s, at various font sizes. With widely varying rendering
technologies in use today, pixel-level control is no longer certain in a TrueType font.
In contrast, printer fonts for the popular Apple LaserWriter were based on PostScript Type 1 outlines, resulting in excellent output at all printer sizes, but failing on the 72 dot per inch Mac screens. Here Adobe provided hand tune bitmaps to cover the small screen fonts, and ugly scaling of any other size on the screen was also provided. Outline fonts have a set of drawing instructions for lines and curves to create a shape for each character (a "glyph"). By following the drawing instructions, the computer creates an "outline" shape at a specific size, and then "fills" it with ink. But this only works down so small, and then Adobe secretly included hints to reach around 18 point. Below this size in the Mac Postscript could not provide on the fly quality outline font scaling.
In an effort to correct this, Sampo Kaasila at Apple decided to write an entirely new format, which he worked on under the name Bass (because it was a scalable font format, and you can scale a fish, and perhaps as in Bass-o-matic 76 from the Saturday Night Live
sketch) and later Royal. In addition, Apple at this time invented an extensible font format the "sfnt" where different parts of the font could be stored in a single file, contrary to PostScript fonts, where bitmaps, metrics data and kerning, and the actual outline font, were in different files.
The system was developed and eventually released as TrueType with the launch of Mac OS System 7
in May 1991. The initial Truetype outline fonts, four-weight families of Times Roman
, Helvetica
, Courier
, and the Pi font replicated the original PostScript fonts of the Apple LaserWriter. Apple also replaced some of their bitmap fonts used by the graphical user interface of previous Macintosh System versions, including, Geneva, Monaco and New York, with scalable Truetype outline fonts. For compatibility with older systems, Apple shipped these fonts, a TrueType Extension
and a TrueType-aware version of Font/DA Mover for System Software 6. For compatibility with the Laserwriter II, Apple developed fonts like ITC Bookman and ITC Chancery in Truetype format.
All of these fonts could now scale to all sizes on screen and printer, making the Macintosh OS7 the first to work without any bitmap fonts. The early TrueType systems being still part of Apple's QuickDraw graphics subsystem, did not render Type 1 fonts on-screen as they do today. At the time, many users had already invested considerable money in Adobe's still proprietary Type 1 fonts. As part of Apple's tactic of opening the font format versus Adobe's desire to keep it closed to all but Adobe licensees, Apple licensed TrueType to Microsoft
. When TrueType and the license to Microsoft was announced, John Warnock
of Adobe gave an impassioned speech in which he claimed Apple and Microsoft were selling snake oil
, and then announced that the Type 1 format was open for anyone to use.
Meanwhile, in exchange for Truetype, Apple got a license for TrueImage
, a PostScript
-compatible page description language owned by Microsoft that Apple could use in their laser printer
s.This was never actually included in any Apple products when a later deal was struck between Apple and Adobe, where Adobe promised to put a TrueType interpreter in their PostScript printer boards, Apple renewed its agreements with Adobe for the use of PostScript in its printers; resulting in lower royalty payments to Adobe who was beginning to license printer controllers capable of competing directly with Apple's LaserWriter printers.
Part of Adobe
's response to learning that TrueType was being developed was to create the Adobe Type Manager
software to scale Type 1 fonts for anti-aliased output on-screen. Although ATM initially cost money, rather than coming free with the operating system, it became a de facto standard for anyone involved in desktop publishing
. Anti-aliased rendering, combined with Adobe applications ability to zoom in to read small type, further combined with the now open PostScript Type 1 font format, provided the impetus for an explosion in font design, and desktop publishing of newspapers and magazines.
Apple extended TrueType with the launch of TrueType GX in 1994, with additional tables in the sfnt that was part of QuickDraw GX
. This offered powerful extensions in two main areas. First was font axes (morphing
), for example allowing fonts to be smoothly adjusted from light to bold or from narrow to extended — competition for Adobe's "multiple master
" technology. Second was Line Layout Manager where particular sequences of characters can be coded to flip to different designs in certain circumstances, useful for example to offer ligatures
for "fi", "ffi", "ct", etc. while maintaining the backing store of characters necessary for spell-checkers and text searching. However, the lack of user-friendly tools for making TrueType GX fonts meant there were no more than a handful of GX fonts.
Much of the technology in TrueType GX, including morphing and substitution, lives on as AAT (Apple Advanced Typography
) in Mac OS X
. Few font developers outside Apple attempt to make AAT fonts; instead, OpenType
has become the dominant sfnt format despite its lack of support for axes or multiple masters.
3.1 operating system. In partnership with their contractors, Monotype Corporation
, Microsoft spent much effort creating a set of high quality TrueType fonts that were compatible with the core fonts being bundled with PostScript equipment at the time. This included the fonts that are standard with Windows to this day: Times New Roman (compatible with Times Roman), Arial
(compatible with Helvetica) and Courier New (compatible with Courier). One should understand "compatible" to mean two things: first, that the fonts are similar in appearance, and second — and very importantly — the fonts have the same character widths, and so can be used to typeset the same documents without reflowing the text.
Microsoft and Monotype technicians used TrueType's hinting
technology to ensure that these fonts did not suffer from the problem of illegibility at low resolutions, which had previously forced the use of bitmapped fonts for screen display. Subsequent advances in technology have introduced first anti-aliasing
, which smooths the edges of fonts at the expense of a slight blurring, and more recently subpixel rendering
(the Microsoft implementation goes by the name ClearType
), which exploits the pixel structure of LCD based displays to increase the apparent resolution of text. Microsoft has heavily marketed ClearType, and sub-pixel rendering techniques for text are now widely used on all platforms.
Microsoft also developed a "smart font" technology, named TrueType Open in 1994, later renamed to OpenType
in 1996 when it merged support of the Adobe
Type 1 glyph outlines.
and Windows
, although both also include native support for Adobe's Type 1 format and the OpenType
extension to TrueType (since Mac OS X
10.0 and Windows 2000
). While some fonts provided with the new operating systems are now in the OpenType format, most free or inexpensive third-party fonts use plain TrueType.
Increasing resolutions and new approaches to screen rendering have reduced the requirement of extensive TrueType hinting. Apple's rendering approach on Mac OS X ignores almost all the hints in a TrueType font, while Microsoft's ClearType ignores many hints, and according to Microsoft, works best with "lightly hinted" fonts.
project of David Turner attempts to create an independent implementation of the TrueType standard (as well as other font standards in FreeType 2). FreeType is included in many Linux
distributions.
There were potential patent infringements in FreeType 1 because parts of the TrueType hinting
virtual machine were patent
ed by Apple, a fact not mentioned in the TrueType standards. (Patent holders who contribute to standards published by a major standards body such as ISO
are required to disclose the scope of their patents, but TrueType was not such a standard.) FreeType 2 includes an automatic hinter that analyzes glyph
shape
s and attempts to generate hints automatically, thus avoiding the patented technology. The automatic hinter generally improves the appearance of free or cheap fonts, for which hinting is often either nonexistent or automatically generated, but it can degrade the appearance of professional hand-hinted fonts, and does not work well (or at all) for non-Western text that requires a different approach to hinting. As a result, some users chose to enable the patented hinting technology. As of May 2010, all patents related to bytecode hinting have expired worldwide, so FreeType 2.4 now enables these features by default.
s) in TrueType fonts are made of straight line segments and quadratic Bézier curve
s. These curves are mathematically simpler and faster to process than cubic Bézier curves, which are used both in the PostScript
-centered world of graphic design
and in Type 1 fonts. However, most shapes require more points to describe with quadratic curves than cubics. This difference also means that it is not possible to convert Type 1 losslessly to the TrueType format, although in practice it is often possible to do a lossless conversion from TrueType to Type 1.
that executes programs inside the font, processing the "hints
" of the glyph
s. These distort the control points which define the outline, with the intention that the rasterizer produces fewer undesirable features on the glyph. Each glyph's hinting program takes account of the size (in pixels) at which the glyph is to be displayed, as well as other less important factors of the display environment.
Although incapable of receiving input and producing output as normally understood in programming, the TrueType hinting language does offer the other prerequisites of programming languages: conditional branching (IF statements), looping an arbitrary number of times (FOR- and WHILE-type statements), variables (although these are simply numbered slots in an area of memory reserved by the font), and encapsulation of code into functions. Special instructions called delta hints are the lowest level control, moving a control point at just one pixel size.
The hallmark of effective TrueType glyph programming techniques is that it does as much as possible using variables defined just once in the whole font (e.g., stem widths, cap height
, x-height
). This means avoiding delta instructions as much as possible. This helps the font developer to make major changes (e.g., the point at which the entire font's main stems jump from 1 to 2 pixels wide) most of the way through development.
Creating a very well-hinted TrueType font remains a significant amount of work, despite the increased user-friendliness of programs for adding hints to fonts. Many TrueType fonts therefore have only rudimentary hints, or have hinting automatically applied by the font editor, with variable end results.
– an embeddable flag that specifies if author allows embedding of the font file into things like PDF
files and websites. Simple tools exist to modify this flag. These tools have been the subject of controversy over potential copyright issues.
Mac OS included support of TTC starting with Mac OS
8.5. In Mac OS, TTC has file type ttcf.
A TrueType Collection file begins with a ttcf table that allows access to the fonts within the collection by pointing to individual headers for each included font. The fonts within a collection share the same glyph-outline table, though each font can refer to subsets within those outlines in its own manner, through its 'cmap', 'name' and 'loca' tables.
A .ttf extension indicates a regular TrueType font, or an OpenType font with TrueType outlines, while a .ttc extension is reserved for TTCs. An OpenType font with PostScript outlines must have an .otf extension. In principle an OpenType font with TrueType outlines may have an .otf extension, but this has rarely been done in practice.
In Mac OS, OpenType is one of several formats referred to as data-fork fonts, as they lack the classic Mac resource fork.
Like TTC, it can handle multiple fonts within a single file. But unlike TTC, those fonts need not be within the same family.
Suitcases come in resource-fork and data-fork
formats. The resource-fork version was the original suitcase format. Data-fork-only suitcases, which place the resource fork contents into the data fork, were first supported in Mac OS X. A suitcase packed into the data-fork-only format has the extension dfont.
language, TrueType outlines are handled with a PostScript wrapper as Type 42 for name-keyed, or Type 11 for CID-keyed fonts.
Standardization
Standardization is the process of developing and implementing technical standards.The goals of standardization can be to help with independence of single suppliers , compatibility, interoperability, safety, repeatability, or quality....
originally developed by Apple Computer
Apple Computer
Apple 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...
in the late 1980s as a competitor to Adobe
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
's Type 1 fonts used in PostScript
PostScript
PostScript 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...
. TrueType has become the most common format for fonts on both the Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
and Microsoft Windows
Microsoft Windows
Microsoft 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...
operating systems.
The primary strength of TrueType was originally that it offered font
Font
In typography, a font is traditionally defined as a quantity of sorts composing a complete character set of a single size and style of a particular typeface...
developers a high degree of control over precisely how their fonts are displayed, right down to particular pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s, at various font sizes. With widely varying rendering
Rendering (computer graphics)
Rendering is the process of generating an image from a model , by means of computer programs. A scene file contains objects in a strictly defined language or data structure; it would contain geometry, viewpoint, texture, lighting, and shading information as a description of the virtual scene...
technologies in use today, pixel-level control is no longer certain in a TrueType font.
Apple
On the Macintosh, fonts were originally stored in hand-tuned bitmap font files that specified individual pixel locations for a font at a particular size. If the user wanted to see a font at another size, the Font Manager would find the closest match and apply a basic scaling algorithm. When scaled to large sizes the algorithm was of limited use, with the output becoming blocky.In contrast, printer fonts for the popular Apple LaserWriter were based on PostScript Type 1 outlines, resulting in excellent output at all printer sizes, but failing on the 72 dot per inch Mac screens. Here Adobe provided hand tune bitmaps to cover the small screen fonts, and ugly scaling of any other size on the screen was also provided. Outline fonts have a set of drawing instructions for lines and curves to create a shape for each character (a "glyph"). By following the drawing instructions, the computer creates an "outline" shape at a specific size, and then "fills" it with ink. But this only works down so small, and then Adobe secretly included hints to reach around 18 point. Below this size in the Mac Postscript could not provide on the fly quality outline font scaling.
In an effort to correct this, Sampo Kaasila at Apple decided to write an entirely new format, which he worked on under the name Bass (because it was a scalable font format, and you can scale a fish, and perhaps as in Bass-o-matic 76 from the Saturday Night Live
Saturday Night Live
Saturday Night Live is a live American late-night television sketch comedy and variety show developed by Lorne Michaels and Dick Ebersol. The show premiered on NBC on October 11, 1975, under the original title of NBC's Saturday Night.The show's sketches often parody contemporary American culture...
sketch) and later Royal. In addition, Apple at this time invented an extensible font format the "sfnt" where different parts of the font could be stored in a single file, contrary to PostScript fonts, where bitmaps, metrics data and kerning, and the actual outline font, were in different files.
The system was developed and eventually released as TrueType with the launch of Mac OS System 7
System 7 (Macintosh)
System 7 is a single-user graphical user interface-based operating system for Macintosh computers. It was introduced on May 13, 1991 by Apple Computer. It succeeded System 6, and was the main Macintosh operating system until it was succeeded by Mac OS 8 in 1997...
in May 1991. The initial Truetype outline fonts, four-weight families of Times Roman
Times Roman
Times New Roman is a serif typeface commissioned by the British newspaper The Times in 1931, created by Victor Lardent at the English branch of Monotype. It was commissioned after Stanley Morison had written an article criticizing The Times for being badly printed and typographically antiquated...
, Helvetica
Helvetica
Helvetica is a widely used sans-serif typeface developed in 1957 by Swiss typeface designer Max Miedinger with Eduard Hoffmann.-Visual distinctive characteristics:Characteristics of this typeface are:lower case:square dot over the letter i....
, Courier
Courier (typeface)
Courier is a monospaced slab serif typeface designed to resemble the output from a strike-on typewriter. The typeface was designed by Howard "Bud" Kettler in 1955...
, and the Pi font replicated the original PostScript fonts of the Apple LaserWriter. Apple also replaced some of their bitmap fonts used by the graphical user interface of previous Macintosh System versions, including, Geneva, Monaco and New York, with scalable Truetype outline fonts. For compatibility with older systems, Apple shipped these fonts, a TrueType Extension
Extension (Mac OS)
On the Apple Macintosh operating system prior to Mac OS X, extensions were small pieces of code that extended the system's functionality. They were run initially at start-up time, and operated by a variety of mechanisms, including trap patching and other code modifying techniques. Initially an...
and a TrueType-aware version of Font/DA Mover for System Software 6. For compatibility with the Laserwriter II, Apple developed fonts like ITC Bookman and ITC Chancery in Truetype format.
All of these fonts could now scale to all sizes on screen and printer, making the Macintosh OS7 the first to work without any bitmap fonts. The early TrueType systems being still part of Apple's QuickDraw graphics subsystem, did not render Type 1 fonts on-screen as they do today. At the time, many users had already invested considerable money in Adobe's still proprietary Type 1 fonts. As part of Apple's tactic of opening the font format versus Adobe's desire to keep it closed to all but Adobe licensees, Apple licensed TrueType to Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
. When TrueType and the license to Microsoft was announced, John Warnock
John Warnock
John Edward Warnock is an American computer scientist best known as the co-founder with Charles Geschke of Adobe Systems Inc., the graphics and publishing software company. Dr. Warnock was President of Adobe for his first two years and Chairman and CEO for his remaining sixteen years at the company...
of Adobe gave an impassioned speech in which he claimed Apple and Microsoft were selling snake oil
Snake oil
Snake oil is a topical preparation made from the Chinese Water Snake , which is used to treat joint pain. However, the most common usage of the phrase is as a derogatory term for quack medicine...
, and then announced that the Type 1 format was open for anyone to use.
Meanwhile, in exchange for Truetype, Apple got a license for TrueImage
TrueImage
TrueImage is a PostScript-compatible interpreter originally developed by Cal Bauer and Bauer Enterprises and sold to Microsoft in 1989. Microsoft subsequently cross-licensed TrueImage to Apple Computer in exchange for a TrueType license...
, a PostScript
PostScript
PostScript 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...
-compatible page description language owned by Microsoft that Apple could use in their laser printer
Laser printer
A laser printer is a common type of computer printer that rapidly produces high quality text and graphics on plain paper. As with digital photocopiers and multifunction printers , laser printers employ a xerographic printing process, but differ from analog photocopiers in that the image is produced...
s.This was never actually included in any Apple products when a later deal was struck between Apple and Adobe, where Adobe promised to put a TrueType interpreter in their PostScript printer boards, Apple renewed its agreements with Adobe for the use of PostScript in its printers; resulting in lower royalty payments to Adobe who was beginning to license printer controllers capable of competing directly with Apple's LaserWriter printers.
Part of Adobe
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
's response to learning that TrueType was being developed was to create the Adobe Type Manager
Adobe Type Manager
Adobe 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:...
software to scale Type 1 fonts for anti-aliased output on-screen. Although ATM initially cost money, rather than coming free with the operating system, it became a de facto standard for anyone involved in desktop publishing
Desktop publishing
Desktop 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...
. Anti-aliased rendering, combined with Adobe applications ability to zoom in to read small type, further combined with the now open PostScript Type 1 font format, provided the impetus for an explosion in font design, and desktop publishing of newspapers and magazines.
Apple extended TrueType with the launch of TrueType GX in 1994, with additional tables in the sfnt that was part of QuickDraw GX
QuickDraw GX
QuickDraw GX was a replacement for the QuickDraw 2D graphics engine and Printing Manager inside the "classic" Mac OS. Its underlying drawing platform was a resolution-independent object oriented retained mode system, making it much easier for programmers to perform common tasks...
. This offered powerful extensions in two main areas. First was font axes (morphing
Morphing
Morphing is a special effect in motion pictures and animations that changes one image into another through a seamless transition. Most often it is used to depict one person turning into another through technological means or as part of a fantasy or surreal sequence. Traditionally such a depiction...
), for example allowing fonts to be smoothly adjusted from light to bold or from narrow to extended — competition for Adobe's "multiple master
Multiple master fonts
Multiple master fonts are an extension to Adobe Systems' Type 1 PostScript fonts, now mostly superseded by the advent of OpenType...
" technology. Second was Line Layout Manager where particular sequences of characters can be coded to flip to different designs in certain circumstances, useful for example to offer ligatures
Ligature (typography)
In writing and typography, a ligature occurs where two or more graphemes are joined as a single glyph. Ligatures usually replace consecutive characters sharing common components and are part of a more general class of glyphs called "contextual forms", where the specific shape of a letter depends on...
for "fi", "ffi", "ct", etc. while maintaining the backing store of characters necessary for spell-checkers and text searching. However, the lack of user-friendly tools for making TrueType GX fonts meant there were no more than a handful of GX fonts.
Much of the technology in TrueType GX, including morphing and substitution, lives on as AAT (Apple Advanced Typography
Apple Advanced Typography
Apple 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 Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
. Few font developers outside Apple attempt to make AAT fonts; instead, OpenType
OpenType
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...
has become the dominant sfnt format despite its lack of support for axes or multiple masters.
Adoption by Microsoft
To ensure its wide adoption, Apple licensed TrueType to Microsoft for free . By 1991 Microsoft added TrueType into the WindowsMicrosoft Windows
Microsoft 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...
3.1 operating system. In partnership with their contractors, Monotype Corporation
Monotype Corporation
Monotype Imaging Holdings is a Delaware corporation based in Woburn, Massachusetts and specializing in typesetting and typeface design as well as text and imaging solutions for use with consumer electronics devices. Monotype Imaging Holdings is the owner of Monotype Imaging Inc., Linotype,...
, Microsoft spent much effort creating a set of high quality TrueType fonts that were compatible with the core fonts being bundled with PostScript equipment at the time. This included the fonts that are standard with Windows to this day: Times New Roman (compatible with Times Roman), Arial
Arial
Arial, sometimes marketed or displayed in software as Arial MT, is a sans-serif typeface and set of computer fonts. Fonts from the Arial family are packaged with Microsoft Windows, some other Microsoft software applications, Apple Mac OS X and many PostScript 3 computer printers...
(compatible with Helvetica) and Courier New (compatible with Courier). One should understand "compatible" to mean two things: first, that the fonts are similar in appearance, and second — and very importantly — the fonts have the same character widths, and so can be used to typeset the same documents without reflowing the text.
Microsoft and Monotype technicians used TrueType's hinting
Font hinting
Font hinting is the use of mathematical instructions to adjust the display of an outline font so that it lines up with a rasterized grid. At low screen resolutions, hinting is critical for producing a clear, legible text...
technology to ensure that these fonts did not suffer from the problem of illegibility at low resolutions, which had previously forced the use of bitmapped fonts for screen display. Subsequent advances in technology have introduced first anti-aliasing
Anti-aliasing
In digital signal processing, spatial anti-aliasing is the technique of minimizing the distortion artifacts known as aliasing when representing a high-resolution image at a lower resolution...
, which smooths the edges of fonts at the expense of a slight blurring, and more recently subpixel rendering
Subpixel rendering
Subpixel rendering is a way to increase the apparent resolution of a computer's liquid crystal display or Organic Light Emitting Diode display by rendering pixels to take into account the screen type's physical properties...
(the Microsoft implementation goes by the name ClearType
ClearType
ClearType 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...
), which exploits the pixel structure of LCD based displays to increase the apparent resolution of text. Microsoft has heavily marketed ClearType, and sub-pixel rendering techniques for text are now widely used on all platforms.
Microsoft also developed a "smart font" technology, named TrueType Open in 1994, later renamed to OpenType
OpenType
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...
in 1996 when it merged support of the Adobe
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...
Type 1 glyph outlines.
Macintosh and Windows
TrueType has long been the most common format for fonts on both Mac OSMac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
and Windows
Microsoft Windows
Microsoft 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...
, although both also include native support for Adobe's Type 1 format and the OpenType
OpenType
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...
extension to TrueType (since Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
10.0 and Windows 2000
Windows 2000
Windows 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...
). While some fonts provided with the new operating systems are now in the OpenType format, most free or inexpensive third-party fonts use plain TrueType.
Increasing resolutions and new approaches to screen rendering have reduced the requirement of extensive TrueType hinting. Apple's rendering approach on Mac OS X ignores almost all the hints in a TrueType font, while Microsoft's ClearType ignores many hints, and according to Microsoft, works best with "lightly hinted" fonts.
Linux and other platforms
The FreeTypeFreeType
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:...
project of David Turner attempts to create an independent implementation of the TrueType standard (as well as other font standards in FreeType 2). FreeType is included in many Linux
Linux
Linux 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...
distributions.
There were potential patent infringements in FreeType 1 because parts of the TrueType hinting
Font hinting
Font hinting is the use of mathematical instructions to adjust the display of an outline font so that it lines up with a rasterized grid. At low screen resolutions, hinting is critical for producing a clear, legible text...
virtual machine were patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
ed by Apple, a fact not mentioned in the TrueType standards. (Patent holders who contribute to standards published by a major standards body such as ISO
International Organization for Standardization
The 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...
are required to disclose the scope of their patents, but TrueType was not such a standard.) FreeType 2 includes an automatic hinter that analyzes glyph
Glyph
A 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....
shape
Shape
The shape of an object located in some space is a geometrical description of the part of that space occupied by the object, as determined by its external boundary – abstracting from location and orientation in space, size, and other properties such as colour, content, and material...
s and attempts to generate hints automatically, thus avoiding the patented technology. The automatic hinter generally improves the appearance of free or cheap fonts, for which hinting is often either nonexistent or automatically generated, but it can degrade the appearance of professional hand-hinted fonts, and does not work well (or at all) for non-Western text that requires a different approach to hinting. As a result, some users chose to enable the patented hinting technology. As of May 2010, all patents related to bytecode hinting have expired worldwide, so FreeType 2.4 now enables these features by default.
Outlines
The outlines of the characters (or glyphGlyph
A 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....
s) in TrueType fonts are made of straight line segments and quadratic Bézier curve
Bézier curve
A Bézier curve is a parametric curve frequently used in computer graphics and related fields. Generalizations of Bézier curves to higher dimensions are called Bézier surfaces, of which the Bézier triangle is a special case....
s. These curves are mathematically simpler and faster to process than cubic Bézier curves, which are used both in the PostScript
PostScript
PostScript 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...
-centered world of graphic design
Graphic design
Graphic design is a creative process – most often involving a client and a designer and usually completed in conjunction with producers of form – undertaken in order to convey a specific message to a targeted audience...
and in Type 1 fonts. However, most shapes require more points to describe with quadratic curves than cubics. This difference also means that it is not possible to convert Type 1 losslessly to the TrueType format, although in practice it is often possible to do a lossless conversion from TrueType to Type 1.
Hinting language
TrueType systems include a virtual machineVirtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
that executes programs inside the font, processing the "hints
Font hinting
Font hinting is the use of mathematical instructions to adjust the display of an outline font so that it lines up with a rasterized grid. At low screen resolutions, hinting is critical for producing a clear, legible text...
" of the glyph
Glyph
A 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....
s. These distort the control points which define the outline, with the intention that the rasterizer produces fewer undesirable features on the glyph. Each glyph's hinting program takes account of the size (in pixels) at which the glyph is to be displayed, as well as other less important factors of the display environment.
Although incapable of receiving input and producing output as normally understood in programming, the TrueType hinting language does offer the other prerequisites of programming languages: conditional branching (IF statements), looping an arbitrary number of times (FOR- and WHILE-type statements), variables (although these are simply numbered slots in an area of memory reserved by the font), and encapsulation of code into functions. Special instructions called delta hints are the lowest level control, moving a control point at just one pixel size.
The hallmark of effective TrueType glyph programming techniques is that it does as much as possible using variables defined just once in the whole font (e.g., stem widths, cap height
Cap height
In typography, cap height refers to the height of a capital letter above the baseline for a particular typeface. It specifically refers to the height of capital letters that are flat—such as H or I—as opposed to round letters such as O, or pointed letters like A, both of which may display...
, x-height
X-height
In typography, the x-height or corpus size refers to the distance between the baseline and the mean line in a typeface. Typically, this is the height of the letter x in the font , as well as the u, v, w, and z...
). This means avoiding delta instructions as much as possible. This helps the font developer to make major changes (e.g., the point at which the entire font's main stems jump from 1 to 2 pixels wide) most of the way through development.
Creating a very well-hinted TrueType font remains a significant amount of work, despite the increased user-friendliness of programs for adding hints to fonts. Many TrueType fonts therefore have only rudimentary hints, or have hinting automatically applied by the font editor, with variable end results.
Embedding protection
The TrueType format allows for the most basic type of digital rights managementDigital rights management
Digital rights management is a class of access control technologies that are used by hardware manufacturers, publishers, copyright holders and individuals with the intent to limit the use of digital content and devices after sale. DRM is any technology that inhibits uses of digital content that...
– an embeddable flag that specifies if author allows embedding of the font file into things like PDF
Portable Document Format
Portable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....
files and websites. Simple tools exist to modify this flag. These tools have been the subject of controversy over potential copyright issues.
TrueType Collection
TrueType Collection (TTC) is an extension of TrueType format that allows combining multiple fonts into a single file, creating substantial space savings for collection of fonts that only use different glyphs on some characters. They were first available in Chinese, Japanese, and Korean versions of Windows, and supported for all regions in Windows 2000 and later.Mac OS included support of TTC starting with Mac OS
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...
8.5. In Mac OS, TTC has file type ttcf.
Basic
A basic font is composed of multiple tables specified in its header. A table name can have up to 4 letters.A TrueType Collection file begins with a ttcf table that allows access to the fonts within the collection by pointing to individual headers for each included font. The fonts within a collection share the same glyph-outline table, though each font can refer to subsets within those outlines in its own manner, through its 'cmap', 'name' and 'loca' tables.
A .ttf extension indicates a regular TrueType font, or an OpenType font with TrueType outlines, while a .ttc extension is reserved for TTCs. An OpenType font with PostScript outlines must have an .otf extension. In principle an OpenType font with TrueType outlines may have an .otf extension, but this has rarely been done in practice.
In Mac OS, OpenType is one of several formats referred to as data-fork fonts, as they lack the classic Mac resource fork.
Suitcase
The suitcase format for TrueType is used on Mac OS. It adds additional Apple-specific information.Like TTC, it can handle multiple fonts within a single file. But unlike TTC, those fonts need not be within the same family.
Suitcases come in resource-fork and data-fork
Resource fork
The resource fork is a construct of the Mac OS operating system used to store structured data in a file, alongside unstructured data stored within the data fork. A resource fork stores information in a specific form, such as icons, the shapes of windows, definitions of menus and their contents, and...
formats. The resource-fork version was the original suitcase format. Data-fork-only suitcases, which place the resource fork contents into the data fork, were first supported in Mac OS X. A suitcase packed into the data-fork-only format has the extension dfont.
PostScript
In the PostScriptPostScript
PostScript 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, TrueType outlines are handled with a PostScript wrapper as Type 42 for name-keyed, or Type 11 for CID-keyed fonts.
See also
- CleartypeClearTypeClearType 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...
- Embedded TrueType font
- Free software Unicode typefacesFree software Unicode typefacesA few projects exist to provide free and open-source Unicode typefaces, i.e. Unicode typefaces which are open-source and designed to contain glyphs of all Unicode characters. However there are also numerous projects aimed at providing only a certain script, such as the Arabeyes Arabic font...
- GNU FreeFont
- FreeTypeFreeTypeFreeType 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:...
- Online office suite
- OpenTypeOpenTypeOpenType 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...
- PangoPangoPango 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) - TypographyTypographyTypography 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...
- TypefaceTypefaceIn typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....
- UnicodeUnicodeUnicode is a computing industry standard for the consistent encoding, representation and handling of text expressed in most of the world's writing systems...
, UTF-8UTF-8UTF-8 is a multibyte character encoding for Unicode. Like UTF-16 and UTF-32, UTF-8 can represent every character in the Unicode character set. Unlike them, it is backward-compatible with ASCII and avoids the complications of endianness and byte order marks...
, Unicode fontsUnicode typefacesA Unicode font is a computer font that contains a wide range of characters, letters, digits, glyphs, symbols, ideograms, logograms, etc., which are collectively mapped into the standard Universal Character Set, derived from many different languages and scripts from around the world...
. - UniscribeUniscribeUniscribe 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) - Apple Type Services for Unicode ImagingApple Type Services for Unicode ImagingThe 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....
(New Macintosh multilingual text rendering engine) - WorldScriptWorldScriptWorldScript 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) - Web Open Font FormatWeb Open Font FormatThe 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....