Section: Marc Penninga (1)
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ot2kpx - extract kerning information from OpenType fonts
extract the kerning data from OpenType fonts (both otf
formats) and prints it (in afm
format) to "stdout"
OPTIONS AND ARGUMENTS
The OpenType font (in either otf or ttf format).
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
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).
Marc Penninga <email@example.com
Copyright (C) 2005-2013 Marc Penninga.
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
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY
; without even the implied warranty of
or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU
General Public License for more details.
(See the source code for the rest of the story.)
Replaced all "given/when" constructions in the source code by "if"'s,
to avoid warnings about experimental features in Perl 5.18 and later.
Refactored the code, and fixed a number of bugs in the process.
Updated the documentation.
- OPTIONS AND ARGUMENTS
- RECENT CHANGES