OT2KPX(1) Marc Penninga OT2KPX(1)NAMEot2kpx - extract kerning information from OpenType fonts
SYNOPSISot2kpx fontfile
DESCRIPTIONot2kpx extract the kerning data from OpenType fonts (both otf and ttf
formats) and prints it (in afm format) to "stdout".
OPTIONS AND ARGUMENTS
fontfile
The OpenType font (in either otf or ttf format).
RESTRICTIONS
- 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 don't really 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, some
of these features concern (according to the OpenType specification)
"define 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 <marcpenninga@gmail.com>
COPYRIGHT
Copyright (C) 2005-2012 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 autoinst; 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.
RECENT CHANGES
(See the source code for the rest of the story.)
2012-02-01 Refactored the code, and fixed a number of bugs in the
process. Updated the documentation.
fontools 2012-03-06 OT2KPX(1)
