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(dvips.info)Metric files

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Metric files
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  A "metric file" describes properties of the font that are independent
of what the characters actually look like.  Aside from general
information about the font itself, a metric file has two kinds of
information: information about individual characters, organized by
character code, and information about sequences of characters.

  The per-character information specifies the width, height, depth, and
italic correction of each character in the font.  Any might be zero.

  In addition to information on individual characters, the metric file
specifies "kerning", i.e., adding or removing space between particular
character pairs.  It further specifies "ligature" information: when a
sequence of input characters should be typeset as a single (presumably
different) "ligature" character.  For example, it's traditional for the
input `fi' to be typeset as `fi', not as `fi' (with the dot of the `i'
colliding with `f').  (In English, the only common ligatures are fi,
fl, ff, ffi, and ffl.)

  Different typesetting systems use different metric file formats:

   * Each Postscript font has an "Adobe font metrics" (`.afm') file.
     These files are plain text, so you can inspect them easily.  You
     can get AFM files for Adobe's fonts from
     `ftp://ftp.adobe.com/pub/adobe/Fonts/AFMs'.

   * TeX uses "TeX font metrics" (`.tfm') files. When you say `\font =
     FONT' in your TeX document, TeX reads a file named `FONT.tfm'.
     (Well, except for the `texfonts.map' feature; *note Fontmap:
     (kpathsea)Fontmap.).  TeX can then calculate the space occupied by
     characters from the font when typesetting. In addition, the DVI
     drivers you use to print or view the DVI file produced by TeX may
     need to look at the TFM file.

     TFM files are binary (and hence are typically much smaller than AFM
     files). You can use the `tftopl' program (*note tftopl invocation:
     (web2c)tftopl invocation.) that comes with TeX to transform a TFM
     file into a human-readable "property list" (`.pl') file.  You can
     also edit a PL file and transform it back to a TeX-readable TFM
     with the companion program `pltotf' (*note pltotf invocation:
     (web2c)pltotf invocation.).  Editing metrics by hand is not
     something you're likely to want to do often, but the capability is
     there.

   * ATM and other typesetting systems use "printer font metric"
     (`.pfm') files. These are binary files. They are irrelevant in the
     TeX world, and not freely available, so we will not discuss them
     further.

  The Afm2tfm program distributed with Dvips converts an AFM file to a
TFM file and performs other useful transformations as well.  Note:
Invoking afm2tfm.