ot2kpx - extract kerning information from OpenType fonts

       Marc Penninga <marcpenninga@gmail.com>

       Copyright (C) 2005-2025 Marc Penninga.

ot2kpx extract the kerning data from OpenType fonts and prints it to "stdout", either in Adobe's KPX
       format (for adding to an afm file) or as a Luatex custom feature, for use with the "\directlua" command.

       This  program  is  distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
       the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General  Public
       License for more details.

       This program is free software; you can redistribute it and/or modify  it  under  the  terms  of  the  GNU
       General  Public License as published by the Free Software Foundation, either version 2 of the License, or
       (at your option) any later version.  A copy of the GNU General Public License is  included  with  ot2kpx;
       see the file GPLv2.txt.

       ot2kpx - extract kerning information from OpenType fonts

-help
           Print a short help text and exit.

       -version
           Print ot2kpx's version and exit.

       -afm, -kpx
           Output  the  kerning  data  in  Adobe's KPX format, as used in afm files.  This is the default output
           format.

       -lua
           Output the kerning data as a Luatex custom font feature, to be included in a "\directlua" command.

       <fontfile>
           The OpenType font (both otf and ttf format are supported).

       (See the source code for the rest of the story.)

       2019-05-20  Added the -version option.

       2019-04-15  Added the -lua command-line option to get output in Luatex's custom feature format.

fontools                                           2025-01-07                                          OT2KPX(1)

-ot2kpx doesn't implement all of the OpenType specification.  Things that are missing include: support
           for font files containing multiple fonts, LookupTables with LookupTypes other than 2,  "kern"  tables
           with format other than 0 and ValueRecords with other types of data than just XAdvance data.

           Most of these limitations won't matter, since the missing features are rare (the only fonts I know of
           that  use  them  are  the  non-western fonts that come with Adobe Reader). Furthermore, many of these
           features define (according to the OpenType specification) "subtle,device-dependentadjustmentsatspecificfontsizesordeviceresolutions"; since there's no way to express such adjustments in afm
           format, ignoring them seems to be the only option anyway.

       -ot2kpx collects kerning data first from the "kern" table, then from all LookupTables associated  with
           the  "kern"  feature; if a kerning pair occurs multiple times, the first value seen is chosen.  There
           are (or may be) several issues with this approach:

           -   The OpenType specification says that fonts in otf format shouldn't use the "kern" table  at  all,
               just the lookups from the "GPOS" table.  Many such fonts do, however, contain a "kern" table, but
               no "GPOS" table; so we use the "kern" table anyway.

           -   Instead  of  reading  all  LookupTables,  it might be better to let the user specify a script and
               language and process only the LookupTables for those values.  However, at least in  the  fonts  I
               checked,  all  script/language  combinations eventually point to the same "kern" LookupTables, so
               this approach wouldn't make any difference (apart from further complicating the code).

ot2kpx [ -afm | -kpx | -lua ] <fontfile>

       This document describes ot2kpx version 20250107.