NAME¶ot2kpx - extract kerning information from OpenType fonts
SYNOPSIS¶ot2kpx [ -afm | -kpx | -lua ] <fontfile>
DESCRIPTION¶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.
OPTIONS AND ARGUMENTS¶
- Print a short help text and exit.
- 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.
- Output the kerning data as a Luatex custom font feature, to be included in a "\directlua" command.
- The OpenType font (both otf and ttf format are supported).
- 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-dependent adjustments at specific font sizes or device resolutions"; 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).
AUTHOR¶Marc Penninga <firstname.lastname@example.org>
COPYRIGHT¶Copyright (C) 2005-2020 Marc Penninga.
LICENSE¶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.
DISCLAIMER¶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.
VERSION¶This document describes ot2kpx version 20200129.
RECENT CHANGES¶(See the source code for the rest of the story.)
- Added the -version option.
- Added the -lua command-line option to get output in Luatex's custom feature format.