pip3 install git+https://github.com/adobe-type-tools/python-modules
This tool exports the kerning and groups data within a UFO to a
makeotf-compatible GPOS kern feature file.
- writing of a sorted kern.fea file, which organizes pairs in order of specificity (exceptions first, then glyph-to-glyph, then group pairs)
- filtering of small pairs (often results of interpolation).
Exceptions (even though they may be small) are not filtered. - processing of right-to-left pairs (given that kerning groups containing
those glyphs are suffixed with
_ARA,_HEB, or_RTL)
- dissolving single-element groups into glyph pairs – this helps with subtable optimization, and can be seen as a means to avoid kerning overflow
- subtable measuring and automatic insertion of subtable breaks
- specifying a maximum subtable size
- identification of glyph-to-glyph RTL pairs by way of a global
RTL_KERNINGreference group - specifying a glyph name suffix for glyphs to be ignored when writing the kern feature
# write a basic kern feature file
python kernFeatureWriter.py font.ufo
# write a kern feature file with minimum absolute kerning value of 5
python kernFeatureWriter.py -min 5 font.ufo
# write a kern feature with subtable breaks
python kernFeatureWriter.py -s font.ufo
# further usage information
python kernFeatureWriter.py -h
This tool interprets glyphs and anchor points within a UFO to write a
makeotf-compatible GPOS mark feature file.
The input UFO file needs to have base glyphs and zero-width combining
marks. Base- and mark glyphs attach via anchor pairs (e.g. above and
_above, or top, and _top).
Combining marks must be members of a COMBINING_MARKS reference group.
- writing a
mark.feafile, which contains mark classes/groups, and per-anchor mark-to-base positioning lookups (GPOS lookup type 4) - writing mark-to-ligature positioning lookups (GPOS lookup type 5).
This requires anchor names to be suffixed with an ordinal (
1ST,2ND,3RD, etc). For example – if a mark with an_aboveanchor is to be attached to a ligature, the ligature’s anchor names would beabove1ST,above2ND, etc – depending on the amount of ligature elements.
-
writing
mkmk.fea, for mark-to-mark positioning (GPOS lookup type 6) -
writing
abvm.fea/blwm.feafiles, as used in Indic scripts (anchor pairs areabvm,_abvm, andblwm,_blwm, respectively) -
writing mark classes into a separate file (in case classes need to be shared across multiple lookup types)
-
trimming casing tags (
UC,LC, orSC)Trimming tags is a somewhat specific feature, but it is quite essential: In a UFO, anchors can be used to build composite glyphs – for example
aacute, andAacute. Since those glyphs would often receive a differently-shaped accent, the anchor pairs (on basesa/Aand marksacutecmb/acutecmb.cap) would beaboveLC/_aboveLC, andaboveUC/_aboveUC, respectively.When writing the mark feature, we care more about which group of combining marks triggers a certain behavior, so removing those casing tags allows grouping all
_abovemarks together, hence attaching to a base glyph – no matter if it is upper- or lowercase. The aesthetic substitution of the mark (e.g. smaller mark on the uppercase letter) can happen later, in theccmpfeature.
# write a basic mark feature
python markFeatureWriter.py font.ufo
# write mark and mkmk feature files
python markFeatureWriter.py -m font.ufo
# trim casing tags
python markFeatureWriter.py -t font.ufo
# further usage information
python markFeatureWriter.py -h
Both kern- and mark feature writers export raw feature data, which still needs to be wrapped with feature “fence”. This is easily achieved with an include statement:
feature kern{
include(kern.fea);
} kern;
The benefit of this is that different feature flags can be used (example), or that mark groups can be shared across mark/mkmk features. Also, the (sometimes volatile) GPOS feature data can be re-generated periodically without affecting the overall structure of the feature tree.
flKernExport.py
FLS5 script to export class kerning to UFO. Superseded by vfb3ufo.
Other modules are FontLab scripts which were used in pre-UFO days in a FLS5 environment. Those modules are not in active development.
-
AdobeFontLabUtils.py
Support module for FontLab scripts. Defines commonly used functions and globals. -
BezChar.py
This module converts between a FontLab glyph and a bez file data string. Used by the OutlineCheck and AutoHint scripts, to convert FL glyphs to bez programs as needed by C libraries that do the hard work. -
WriteFeaturesKernFDK.py
Former kern feature writer. -
WriteFeaturesMarkFDK.py
Former mark feature writer.
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