Metafont
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| Developer(s) | Donald Knuth |
|---|---|
| Stable release |
2.7182818 / January 2014
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| Operating system | Cross-platform |
| Type | Computer language |
| License | Permissive |
| Website | www |
Metafont is a description 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. Metafont was devised by Donald Knuth as a counterpart to his TeX typesetting system.
One of the characteristics of Metafont is that all of the shapes of the glyphs are defined with geometrical equations. In particular, one can define a given point to be the intersection of a line segment and a Bézier cubic.
Unlike more common outline font formats (such as TrueType or PostScript Type 1), a Metafont font is primarily made up of strokes with finite-width "pens", along with filled regions. Thus, rather than describing the outline of the glyph directly, a Metafont file describes the pen paths. Some simpler Metafont fonts, such as the calligraphic mathematics fonts in the Computer Modern family, use a single pen stroke with a relatively large pen to define each visual "stroke" of the glyphs. More complex fonts such as the Roman text fonts in the Computer Modern family use a small pen to trace around the outline of the visual "strokes", which are then filled; the result is much like an outline font, but with slightly softened corners defined by the pen shape.
Since the font shapes are defined by equations rather than directly coded numbers, it is possible to treat parameters such as aspect ratio, font slant, stroke width, serif size, and so forth as input parameters in each glyph definition (which then define not a single font, but a meta-font). Thus, by changing the value of one of these parameters at one location in the Metafont file, one can produce a consistent change throughout the entire font. Computer Modern Roman illustrates many uses of this feature; a typical TeX installation includes a number of versions of the font in sizes from 5pt to 17pt, with the stroke widths the same in all sizes (rather than increasing as the font is scaled up) and aspect ratios widening in the smaller sizes for increased legibility. In addition, the Computer Modern typewriter and sans-serif fonts are defined using essentially the same Metafont file as the Roman font, but with different global parameters.
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