Computer font - AbsoluteAstronomy.com

This article is about font technology. For information about the typographic appearance of individual font sets, see Typeface
Typeface
In 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....

s.

A computer font (or font) is an electronic data file

Data file

A data file is a computer file which stores data to use by a computer application or system. It generally does not refer to files that contain instructions or code to be executed , or to files which define the operation or structure of an application or system ; but specifically to information...

containing a set of 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, characters, or symbols such as dingbat

Dingbat

A dingbat is an ornament, character or spacer used in typesetting, sometimes more formally known as a "printer's ornament" or "printer's character"....

s. Although the term 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...

first referred to a set of metal type sorts in one style and size, since the 1990s it is generally used to refer to a scalable set of digital shapes that may be printed at many different sizes.

There are three basic kinds of computer font file data formats:

Raster fonts consist of a matrix (or bitmap) of dots or 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 representing the image of each glyph in each face and size.
Outline fonts (also called vector fonts) use 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, drawing instructions and mathematical formulae to describe each glyph, which make the character outlines scalable to any size.
Stroke fonts use a series of specified lines and additional information to define the profile, or size and shape of the line in a specific face, which together describe the appearance of the glyph.

Raster fonts are faster and easier to use in computer code, but non-scalable, requiring a separate font for each size. Outline and stroke fonts can be resized using a single font and substituting different measurements for components of each glyph, but are somewhat more complicated to render on screen than raster fonts, as they require additional computer code to render the outline to a bitmap for display on screen or in print. Although all types are still in use, most fonts seen and used on computers are outline fonts.

A raster image can be displayed in a different size only with some distortion, but renders quickly; outline or stroke image formats are resizable but take more time to render as pixels must be drawn from scratch each time they are displayed.

Fonts are designed and created using font editor

Font editor

A font editor is a class of application software specifically designed to create or modify computer font files.Font editors differ greatly depending if they are designed to edit bitmap fonts or outline fonts. Modern font editors mostly deal with the outline fonts, because bitmap fonts are an older...

s. Fonts specifically designed for the computer screen and not printing are known as screenfont

Screenfont

A screenfont or screen font is:* a computer typeface created specifically for reading from a screen; or* another kind of typeface, like a print font, that is used for reading from a screen...

s.

Fonts can be monospaced

Monospace (font)

Monospace is a monospaced Unicode font, developed by George Williams.This font contains 2,862 glyphs. It includes characters in the following unicode ranges: Basic Latin, Latin-1 Supplement, Latin Extended-A, Latin Extended-B, IPA Extensions, Spacing Modifier Letters, Combining Diacritical Marks,...

(i.e.. every character is plotted a constant distance from the previous character that it is next to, while drawing) or proportional (each character has its own width). However, the particular font-handling application can affect the spacing, particularly when doing justification

Justification

Justification may refer to:*Theory of justification, a part of epistemology that attempts to understand the justification of propositions and beliefs*Justification , defence in a prosecution for a criminal offense...

Bitmap fonts

A bitmap font is one that stores each 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....

as an array of pixels (that is, a bitmap

Bitmap

In computer graphics, a bitmap or pixmap is a type of memory organization or image file format used to store digital images. The term bitmap comes from the computer programming terminology, meaning just a map of bits, a spatially mapped array of bits. Now, along with pixmap, it commonly refers to...

). It is less commonly known as a raster font. Bitmap fonts are simply collections of raster images

Raster graphics

In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...

of glyphs. For each variant of the font, there is a complete set of glyph images, with each set containing an image for each character. For example, if a font has three sizes, and any combination of bold and italic, then there must be 12 complete sets of images.

Advantages of bitmap fonts include:

Extremely fast and simple to render
Unscaled bitmap fonts always give exactly the same output
Easier to create than other kinds.

The primary disadvantage of bitmap fonts is that the visual quality tends to be poor when scaled or otherwise transformed, compared to outline and stroke fonts, and providing many optimized and purpose-made sizes of the same font dramatically increases memory usage. The earliest bitmap fonts were only available in certain optimized sizes such as 8, 9, 10, 12, 14, 18, 24, 36, 48, 72, and 96 points, with custom fonts often available in only one specific size, such as a headline font at only 72 points.

The limited processing power and memory of early computer systems forced exclusive use of bitmap fonts. Improvements in hardware have allowed them to be replaced with outline or stroke fonts in cases where arbitrary scaling is desirable, but bitmap fonts are still in common use in embedded systems and other places where speed and simplicity are considered important.

Bitmap fonts are used in the 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...

console, the 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...

recovery console

Recovery Console

The Recovery Console is a feature of the Windows 2000, Windows XP and Windows Server 2003 operating systems. It provides the means for administrators to perform a limited range of tasks using a command line interface. Its primary function is to enable administrators to recover from situations...

, and embedded systems. Older dot matrix printer

Dot matrix printer

A dot matrix printer or impact matrix printer is a type of computer printer with a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like the print mechanism on a typewriter...

s used bitmap fonts; often stored in the memory of the printer and addressed by the computer's print driver. Bitmap fonts may be used in cross-stitch

Cross-stitch

Cross-stitch is a popular form of counted-thread embroidery in which X-shaped stitches in a tiled, raster-like pattern are used to form a picture. Cross-stitch is often executed on easily countable evenweave fabric called aida cloth. The stitcher counts the threads in each direction so that the...

.

To draw a string using a bitmap font, means to successively output bitmaps of each character that the string comprises, performing per-character indentation.

Monochrome fonts vs. fonts with shades of gray

Digital bitmap fonts (and the final rendering of vector fonts

Font rasterization

Font rasterization is the process of converting text from a vector description to a raster or bitmap description. This often involves some anti-aliasing on screen text to make it smoother and easier to read...

) may use monochrome

Monochrome

Monochrome describes paintings, drawings, design, or photographs in one color or shades of one color. A monochromatic object or image has colors in shades of limited colors or hues. Images using only shades of grey are called grayscale or black-and-white...

or shades of gray

Grayscale

In photography and computing, a grayscale or greyscale digital image is an image in which the value of each pixel is a single sample, that is, it carries only intensity information...

. The latter is anti-aliased

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...

. When displaying a text, typically an operating system properly represents the "shades of gray" as intermediate colors between the color of the font and that of the background. However, if the text is represented as an image with transparent background, "shades of gray" require an image format allowing partial transparency

Alpha compositing

In computer graphics, alpha compositing is the process of combining an image with a background to create the appearance of partial or full transparency. It is often useful to render image elements in separate passes, and then combine the resulting multiple 2D images into a single, final image in a...

Scaling

Bitmap fonts look best at their native 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....

size. Some systems using bitmap fonts can create some font variants algorithmically. For example, the original Apple Macintosh computer could produce bold by widening vertical strokes and oblique by shearing the image. At non-native sizes, many text rendering systems perform nearest-neighbor resampling, introducing ugly jagged edges. More advanced systems perform 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...

on bitmap fonts whose size does not match the size that the application requests. This technique works well for making the font smaller but not as well for increasing the size, as it tends to blur the edges. Some graphics systems that use bitmap fonts, especially those of emulator

Emulator

In computing, an emulator is hardware or software or both that duplicates the functions of a first computer system in a different second computer system, so that the behavior of the second system closely resembles the behavior of the first system...

s, apply curve-sensitive nonlinear resampling algorithms such as 2xSaI or hq3x on fonts and other bitmaps, which avoids blurring the font while introducing little objectionable distortion at moderate increases in size.

The difference between bitmap fonts and outline fonts is similar to the difference between bitmap and vector image file formats. Bitmap fonts are like image formats such as Windows Bitmap
Windows bitmap
The BMP File Format, also known as Bitmap Image File or Device Independent Bitmap file format or simply a Bitmap, is a Raster graphics image file format used to store bitmap digital images, independently of the display device , especially on Microsoft Windows and OS/2 operating systems.The BMP...

(.bmp), Portable Network Graphics (.png) and Tagged Image Format (.tif or .tiff), which store the image data as a grid of pixels, in some cases with compression. Outline or stroke image formats such as Windows Metafile
Windows Metafile
Windows Metafile is a graphics file format on Microsoft Windows systems, originally designed in the 1990s. Windows Metafiles are intended to be portable between applications and may contain both vector graphics and bitmap components....

format (.wmf) and Scalable Vector Graphics
Scalable Vector Graphics
Scalable Vector Graphics is a family of specifications of an XML-based file format for describing two-dimensional vector graphics, both static and dynamic . The SVG specification is an open standard that has been under development by the World Wide Web Consortium since 1999.SVG images and their...

format (.svg), store instructions in the form of lines and curves of how to draw the image rather than storing the image itself.

A "trace" program can follow the outline of a high-resolution bitmap font and create an initial outline that a font designer uses to create an outline font useful in systems such as 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...

or TrueType

TrueType

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...

. Outline fonts scale easily without jagged edges or blurriness.

Bitmap font formats

Portable Compiled Format
Portable Compiled Format
Portable Compiled Format is a bitmap font format used by Xserver in its core font system, and have been used for decades. PCF fonts are usually installed, by default, on most Unix based operating systems, and are used in terminals such as xterm. PCF fonts replaced BDF due to a slight efficiency...

(PCF)
Glyph Bitmap Distribution Format
Glyph Bitmap Distribution Format
The Glyph Bitmap Distribution Format by Adobe is a file format for storing bitmap fonts. The content is presented as a text file that is intended to be human and computer readable. BDF is typically used in Unix environments.-Overview:...

(BDF)
Server Normal Format
Server Normal Format
Server Normal Format is a bitmap font format used by X Window. It is one of the oldest X Window font formats. Nowadays it is rarely used, however it is still supported by the latest X.org server. SNF fonts had the problem of being platform dependent, therefore it needed to be compiled on each...

(SNF)
DECWindows Font (DWF)
Sun X11/NeWS format (BF, AFM)
Microsoft Windows bitmapped font (FON)
Amiga Font, ColorFont, AnimFont
ByteMap Font (BMF)
PC Screen Font (PSF)
Packed bitmap font bitmap file for TeX DVI drivers (PK)

Outline fonts

Outline fonts or vector fonts are collections of vector images

Vector graphics

Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygon, which are all based on mathematical expressions, to represent images in computer graphics...

, i.e. a set of lines and curves to define the border of glyphs. Early vector fonts were used by vector monitor

Vector monitor

A vector monitor or vector display is a display device used for early computers. It is a type of CRT, similar to the oscilloscope, but typically uses magnetic, rather than electrostatic, deflection...

s and vector plotters

Plotter

A plotter is a computer printing device for printing vector graphics. In the past, plotters were widely used in applications such as computer-aided design, though they have generally been replaced with wide-format conventional printers...

using their own internal fonts, usually with thin single strokes instead of thick outlined glyphs. The advent of desktop publishing brought the need for a universal standard to integrate the graphical user interface

Graphical user interface

In computing, a graphical user interface is a type of user interface that allows users to interact with electronic devices with images rather than text commands. GUIs can be used in computers, hand-held devices such as MP3 players, portable media players or gaming devices, household appliances and...

of the first Macintosh

Macintosh

The Macintosh , or Mac, is a series of several lines of personal computers designed, developed, and marketed by Apple Inc. The first Macintosh was introduced by Apple's then-chairman Steve Jobs on January 24, 1984; it was the first commercially successful personal computer to feature a mouse and a...

and 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. The term to describe the integration technology was WYSIWYG

WYSIWYG

WYSIWYG is an acronym for What You See Is What You Get. The term is used in computing to describe a system in which content displayed onscreen during editing appears in a form closely corresponding to its appearance when printed or displayed as a finished product...

(What You See Is What You Get). The universal standard was (and still is) Adobe PostScript

PostScript

. Examples are PostScript Type 1 and Type 3 fonts, TrueType

TrueType

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...

and 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...

.

The primary advantage of outline fonts is that they can be easily transformed by applying a mathematical function to each vector point, scaling them without causing pixellation. Outline font characters can be scaled to any size and otherwise transformed with more attractive results than bitmap fonts, but requires considerably more processing and may yield undesirable rendering, depending on the font, rendering software, and output size.

Outline fonts have a major problem, in that 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 cannot be rendered accurately onto a raster display (such as most computer monitors and printers), and their rendering can change shape depending on the desired size and position. Measures such as font 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...

have to be used to reduce the visual impact of this problem, which require sophisticated software that is difficult to implement correctly. Many modern desktop computer systems include software to do this, but they use considerably more processing power than bitmap fonts, and there can be minor rendering defects, particularly at small font sizes. Despite this, they are frequently used because people often consider the processing time and defects to be acceptable when compared to the ability to scale fonts freely.

Stroke-based fonts

A glyph's outline is defined by the vertices of individual strokes and stroke's profile. Its advantages over outline fonts include reducing number of vertices needed to define a glyph, allowing the same vertices to be used to generate a font with a different weight, glyph width, or serifs using different stroke rules, and the associated size savings. For a font developer, editing a glyph by stroke is easier and less prone to error than editing outlines. A stroke-based system also allows scaling glyphs in height or width without altering stroke thickness of the base glyphs. Stroke-based fonts are heavily marketed for East Asian markets for use on embedded devices, but the technology is not limited to ideogram

Ideogram

An ideogram or ideograph is a graphic symbol that represents an idea or concept. Some ideograms are comprehensible only by familiarity with prior convention; others convey their meaning through pictorial resemblance to a physical object, and thus may also be referred to as pictograms.Examples of...

s.

Commercial developers included Agfa Monotype (iType), Type Solutions, Inc. (owned by Bitstream Inc.

Bitstream Inc.

Bitstream Inc. is a type foundry that produces digital typefaces . Founded in 1981 by Matthew Carter and Mike Parker among others, it claims to be the oldest such company...

) (Font Fusion (FFS), btX2), Fontworks (Gaiji Master), which have independently developed stroke-based font types and font engines.

Although Monotype and Bitstream have claimed tremendous space saving using stroke-based fonts on East Asian character sets, most of the space saving comes from building composite glyphs, which is part of the TrueType specification and does not require stroke-based approach.

Type 1 and Type 3 fonts

Type 1 and Type 3 fonts were developed by Adobe

Adobe Systems

Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...

for professional digital typesetting. Using PostScript

PostScript

, the glyphs are outline fonts described with cubic Bezier curves. Type 1 fonts were restricted to a subset of the PostScript language, and used Adobe's hinting system, which used to be very expensive. Type 3 allowed unrestricted use of the PostScript language, but didn't include any hint information, which could lead to visible rendering artifacts on low-resolution devices (such as computer screens and dot-matrix printers).

TrueType font

TrueType

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...

is a font system originally developed by Apple Inc. It was intended to replace Type 1 fonts, which many felt were too expensive. Unlike Type 1 fonts, TrueType glyphs are described with quadratic Bezier curves. It is currently very popular and implementations exist for all major operating systems. MT Extra is the smallest TrueType font.

OpenType font

OpenType

is a smartfont system designed by Adobe

Adobe Systems

Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...

and 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...

. OpenType fonts contain outlines in either the TrueType or Type 1 (actually CFF) format together with a wide range of metadata. MS Outlook is the smallest OpenType font.

METAFONT

Metafont is a programming language used to define vector fonts. It is also the name of the interpreter that executes Metafont code, generating the bitmap fonts that can be embedded into e.g. PostScript...

uses a different sort of glyph description. Like TrueType, it is a vector font description system. It draws glyphs using strokes produced by moving a polygonal or elliptical pen approximated by a polygon along a path made from cubic Bézier splines and straight line segments, or by filling such paths. Although when stroking a path the envelope of the stroke is never actually generated, the method causes no loss of accuracy or resolution.

External links

Finding Fonts FAQ (Microsoft)
Font Technologies chapter of the LDP's Font-HOWTO
Microsoft's font guide
Archive of freely downloadable fonts - More than 15 000 fonts
Rare Tattoo Fonts
Search Free Fonts - One of the biggest free font collections on web
Font Browser
Glossary of Font Terms Over 50 entries with helpful diagram.
History and technology of computer fonts, Annals of the History of Computing, IEEE, Apr-Jun 1998, Vol. 20, Issue 2, pages 30-34, ISSN 1058-6180.

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.

Bitmap fonts

Monochrome fonts vs. fonts with shades of gray

Scaling

Bitmap font formats

Outline fonts

Stroke-based fonts

Type 1 and Type 3 fonts

TrueType font

OpenType font

METAFONT

See also

External links