subset: Generate subsets of fonts or optimize file sizes

pyftsubset – OpenType font subsetter and optimizer

pyftsubset is an OpenType font subsetter and optimizer, based on fontTools. It accepts any TT- or CFF-flavored OpenType (.otf or .ttf) or WOFF (.woff) font file. The subsetted glyph set is based on the specified glyphs or characters, and specified OpenType layout features.

The tool also performs some size-reducing optimizations, aimed for using subset fonts as webfonts. Individual optimizations can be enabled or disabled, and are enabled by default when they are safe.

Usage: pyftsubset font-file [glyph…] [–option=value]…

At least one glyph or one of –gids, –gids-file, –glyphs, –glyphs-file, –text, –text-file, –unicodes, or –unicodes-file, must be specified.

Args:

font-file

The input font file.

glyph

Specify one or more glyph identifiers to include in the subset. Must be PS glyph names, or the special string ‘*’ to keep the entire glyph set.

Initial glyph set specification

These options populate the initial glyph set. Same option can appear multiple times, and the results are accummulated.

–gids=<NNN>[,<NNN>…]

Specify comma/whitespace-separated list of glyph IDs or ranges as decimal numbers. For example, –gids=10-12,14 adds glyphs with numbers 10, 11, 12, and 14.

--gids-file=<path>

Like –gids but reads from a file. Anything after a ‘#’ on any line is ignored as comments.

–glyphs=<glyphname>[,<glyphname>…]

Specify comma/whitespace-separated PS glyph names to add to the subset. Note that only PS glyph names are accepted, not gidNNN, U+XXXX, etc that are accepted on the command line. The special string ‘*’ will keep the entire glyph set.

--glyphs-file=<path>

Like –glyphs but reads from a file. Anything after a ‘#’ on any line is ignored as comments.

--text=<text>

Specify characters to include in the subset, as UTF-8 string.

--text-file=<path>

Like –text but reads from a file. Newline character are not added to the subset.

–unicodes=<XXXX>[,<XXXX>…]

Specify comma/whitespace-separated list of Unicode codepoints or ranges as hex numbers, optionally prefixed with ‘U+’, ‘u’, etc. For example, –unicodes=41-5a,61-7a adds ASCII letters, so does the more verbose –unicodes=U+0041-005A,U+0061-007A. The special strings ‘*’ will choose all Unicode characters mapped by the font.

--unicodes-file=<path>

Like –unicodes, but reads from a file. Anything after a ‘#’ on any line in the file is ignored as comments.

--ignore-missing-glyphs

Do not fail if some requested glyphs or gids are not available in the font.

--no-ignore-missing-glyphs

Stop and fail if some requested glyphs or gids are not available in the font. [default]

–ignore-missing-unicodes [default]

Do not fail if some requested Unicode characters (including those indirectly specified using –text or –text-file) are not available in the font.

--no-ignore-missing-unicodes

Stop and fail if some requested Unicode characters are not available in the font. Note the default discrepancy between ignoring missing glyphs versus unicodes. This is for historical reasons and in the future –no-ignore-missing-unicodes might become default.

Other options

For the other options listed below, to see the current value of the option, pass a value of ‘?’ to it, with or without a ‘=’. In some environments, you might need to escape the question mark, like this: ‘–glyph-names?’.

Examples:

$ pyftsubset --glyph-names?
Current setting for 'glyph-names' is: False
$ pyftsubset --name-IDs=?
Current setting for 'name-IDs' is: [0, 1, 2, 3, 4, 5, 6]
$ pyftsubset --hinting? --no-hinting --hinting?
Current setting for 'hinting' is: True
Current setting for 'hinting' is: False

Output options

--output-file=<path>

The output font file. If not specified, the subsetted font will be saved in as font-file.subset.

--flavor=<type>

Specify flavor of output font file. May be ‘woff’ or ‘woff2’. Note that WOFF2 requires the Brotli Python extension, available at https://github.com/google/brotli

--with-zopfli

Use the Google Zopfli algorithm to compress WOFF. The output is 3-8 % smaller than pure zlib, but the compression speed is much slower. The Zopfli Python bindings are available at: https://pypi.python.org/pypi/zopfli

--harfbuzz-repacker

By default, we serialize GPOS/GSUB using the HarfBuzz Repacker when uharfbuzz can be imported and is successful, otherwise fall back to the pure-python serializer. Set the option to force using the HarfBuzz Repacker (raises an error if uharfbuzz can’t be found or fails).

--no-harfbuzz-repacker

Always use the pure-python serializer even if uharfbuzz is available.

Glyph set expansion

These options control how additional glyphs are added to the subset.

--retain-gids

Retain glyph indices; just empty glyphs not needed in-place.

--notdef-glyph

Add the ‘.notdef’ glyph to the subset (ie, keep it). [default]

--no-notdef-glyph

Drop the ‘.notdef’ glyph unless specified in the glyph set. This saves a few bytes, but is not possible for Postscript-flavored fonts, as those require ‘.notdef’. For TrueType-flavored fonts, this works fine as long as no unsupported glyphs are requested from the font.

--notdef-outline

Keep the outline of ‘.notdef’ glyph. The ‘.notdef’ glyph outline is used when glyphs not supported by the font are to be shown. It is not needed otherwise.

--no-notdef-outline

When including a ‘.notdef’ glyph, remove its outline. This saves a few bytes. [default]

--recommended-glyphs

Add glyphs 0, 1, 2, and 3 to the subset, as recommended for TrueType-flavored fonts: ‘.notdef’, ‘NULL’ or ‘.null’, ‘CR’, ‘space’. Some legacy software might require this, but no modern system does.

--no-recommended-glyphs

Do not add glyphs 0, 1, 2, and 3 to the subset, unless specified in glyph set. [default]

--no-layout-closure

Do not expand glyph set to add glyphs produced by OpenType layout features. Instead, OpenType layout features will be subset to only rules that are relevant to the otherwise-specified glyph set.

–layout-features[+|-]=<feature>[,<feature>…]

Specify (=), add to (+=) or exclude from (-=) the comma-separated set of OpenType layout feature tags that will be preserved. Glyph variants used by the preserved features are added to the specified subset glyph set. By default, ‘calt’, ‘ccmp’, ‘clig’, ‘curs’, ‘dnom’, ‘frac’, ‘kern’, ‘liga’, ‘locl’, ‘mark’, ‘mkmk’, ‘numr’, ‘rclt’, ‘rlig’, ‘rvrn’, and all features required for script shaping are preserved. To see the full list, try ‘–layout-features=?’. Use ‘*’ to keep all features. Multiple –layout-features options can be provided if necessary. Examples:

–layout-features+=onum,pnum,ss01

  • Keep the default set of features and ‘onum’, ‘pnum’, ‘ss01’.

–layout-features-=’mark’,’mkmk’

  • Keep the default set of features but drop ‘mark’ and ‘mkmk’.

–layout-features=’kern’

  • Only keep the ‘kern’ feature, drop all others.

–layout-features=’’

  • Drop all features.

–layout-features=’*’

  • Keep all features.

–layout-features+=aalt –layout-features-=vrt2

  • Keep default set of features plus ‘aalt’, but drop ‘vrt2’.

–layout-scripts[+|-]=<script>[,<script>…]

Specify (=), add to (+=) or exclude from (-=) the comma-separated set of OpenType layout script tags that will be preserved. LangSys tags can be appended to script tag, separated by ‘.’, for example: ‘arab.dflt,arab.URD,latn.TRK’. By default all scripts are retained (‘*’).

Hinting options

--hinting

Keep hinting [default]

--no-hinting

Drop glyph-specific hinting and font-wide hinting tables, as well as remove hinting-related bits and pieces from other tables (eg. GPOS). See –hinting-tables for list of tables that are dropped by default. Instructions and hints are stripped from ‘glyf’ and ‘CFF ‘ tables respectively. This produces (sometimes up to 30%) smaller fonts that are suitable for extremely high-resolution systems, like high-end mobile devices and retina displays.

Optimization options

--desubroutinize

Remove CFF use of subroutinizes. Subroutinization is a way to make CFF fonts smaller. For small subsets however, desubroutinizing might make the font smaller. It has even been reported that desubroutinized CFF fonts compress better (produce smaller output) WOFF and WOFF2 fonts. Also see note under –no-hinting.

–no-desubroutinize [default]

Leave CFF subroutinizes as is, only throw away unused subroutinizes.

Font table options

–drop-tables[+|-]=<table>[,<table>…]

Specify (=), add to (+=) or exclude from (-=) the comma-separated set of tables that will be be dropped. By default, the following tables are dropped: ‘BASE’, ‘JSTF’, ‘DSIG’, ‘EBDT’, ‘EBLC’, ‘EBSC’, ‘PCLT’, ‘LTSH’ and Graphite tables: ‘Feat’, ‘Glat’, ‘Gloc’, ‘Silf’, ‘Sill’. The tool will attempt to subset the remaining tables.

Examples:

--drop-tables-=BASE

  • Drop the default set of tables but keep ‘BASE’.

–drop-tables+=GSUB

  • Drop the default set of tables and ‘GSUB’.

--drop-tables=DSIG

  • Only drop the ‘DSIG’ table, keep all others.

–drop-tables=

  • Keep all tables.

–no-subset-tables+=<table>[,<table>…]

Add to the set of tables that will not be subsetted. By default, the following tables are included in this list, as they do not need subsetting (ignore the fact that ‘loca’ is listed here): ‘gasp’, ‘head’, ‘hhea’, ‘maxp’, ‘vhea’, ‘OS/2’, ‘loca’, ‘name’, ‘cvt ‘, ‘fpgm’, ‘prep’, ‘VMDX’, ‘DSIG’, ‘CPAL’, ‘MVAR’, ‘cvar’, ‘STAT’. By default, tables that the tool does not know how to subset and are not specified here will be dropped from the font, unless –passthrough-tables option is passed.

Example:

–no-subset-tables+=FFTM

  • Keep ‘FFTM’ table in the font by preventing subsetting.

--passthrough-tables

Do not drop tables that the tool does not know how to subset.

--no-passthrough-tables

Tables that the tool does not know how to subset and are not specified in –no-subset-tables will be dropped from the font. [default]

–hinting-tables[-]=<table>[,<table>…]

Specify (=), add to (+=) or exclude from (-=) the list of font-wide hinting tables that will be dropped if –no-hinting is specified.

Examples:

--hinting-tables-=VDMX

  • Drop font-wide hinting tables except ‘VDMX’.

–hinting-tables=

  • Keep all font-wide hinting tables (but strip hints from glyphs).

--legacy-kern

Keep TrueType ‘kern’ table even when OpenType ‘GPOS’ is available.

--no-legacy-kern

Drop TrueType ‘kern’ table if OpenType ‘GPOS’ is available. [default]

Font naming options

These options control what is retained in the ‘name’ table. For numerical codes, see: http://www.microsoft.com/typography/otspec/name.htm

–name-IDs[+|-]=<nameID>[,<nameID>…]

Specify (=), add to (+=) or exclude from (-=) the set of ‘name’ table entry nameIDs that will be preserved. By default, only nameIDs between 0 and 6 are preserved, the rest are dropped. Use ‘*’ to keep all entries.

Examples:

–name-IDs+=7,8,9

  • Also keep Trademark, Manufacturer and Designer name entries.

–name-IDs=

  • Drop all ‘name’ table entries.

–name-IDs=*

  • keep all ‘name’ table entries

--name-legacy

Keep legacy (non-Unicode) ‘name’ table entries (0.x, 1.x etc.). XXX Note: This might be needed for some fonts that have no Unicode name entires for English. See: https://github.com/fonttools/fonttools/issues/146

--no-name-legacy

Drop legacy (non-Unicode) ‘name’ table entries [default]

–name-languages[+|-]=<langID>[,<langID>]

Specify (=), add to (+=) or exclude from (-=) the set of ‘name’ table langIDs that will be preserved. By default only records with langID 0x0409 (English) are preserved. Use ‘*’ to keep all langIDs.

--obfuscate-names

Make the font unusable as a system font by replacing name IDs 1, 2, 3, 4, and 6 with dummy strings (it is still fully functional as webfont).

Glyph naming and encoding options

--glyph-names

Keep PS glyph names in TT-flavored fonts. In general glyph names are not needed for correct use of the font. However, some PDF generators and PDF viewers might rely on glyph names to extract Unicode text from PDF documents.

--no-glyph-names

Drop PS glyph names in TT-flavored fonts, by using ‘post’ table version 3.0. [default]

--legacy-cmap

Keep the legacy ‘cmap’ subtables (0.x, 1.x, 4.x etc.).

--no-legacy-cmap

Drop the legacy ‘cmap’ subtables. [default]

--symbol-cmap

Keep the 3.0 symbol ‘cmap’.

--no-symbol-cmap

Drop the 3.0 symbol ‘cmap’. [default]

Other font-specific options

--recalc-bounds

Recalculate font bounding boxes.

--no-recalc-bounds

Keep original font bounding boxes. This is faster and still safe for all practical purposes. [default]

--recalc-timestamp

Set font ‘modified’ timestamp to current time.

--no-recalc-timestamp

Do not modify font ‘modified’ timestamp. [default]

--canonical-order

Order tables as recommended in the OpenType standard. This is not required by the standard, nor by any known implementation.

--no-canonical-order

Keep original order of font tables. This is faster. [default]

--prune-unicode-ranges

Update the ‘OS/2 ulUnicodeRange*’ bits after subsetting. The Unicode ranges defined in the OpenType specification v1.7 are intersected with the Unicode codepoints specified in the font’s Unicode ‘cmap’ subtables: when no overlap is found, the bit will be switched off. However, it will not be switched on if an intersection is found. [default]

--no-prune-unicode-ranges

Don’t change the ‘OS/2 ulUnicodeRange*’ bits.

--prune-codepage-ranges

Update the ‘OS/2 ulCodePageRange*’ bits after subsetting. [default]

--no-prune-codepage-ranges

Don’t change the ‘OS/2 ulCodePageRange*’ bits.

--recalc-average-width

Update the ‘OS/2 xAvgCharWidth’ field after subsetting.

--no-recalc-average-width

Don’t change the ‘OS/2 xAvgCharWidth’ field. [default]

--recalc-max-context

Update the ‘OS/2 usMaxContext’ field after subsetting.

--no-recalc-max-context

Don’t change the ‘OS/2 usMaxContext’ field. [default]

--font-number=<number>

Select font number for TrueType Collection (.ttc/.otc), starting from 0.

--pretty-svg

When subsetting SVG table, use lxml pretty_print=True option to indent the XML output (only recommended for debugging purposes).

Application options

--verbose

Display verbose information of the subsetting process.

--timing

Display detailed timing information of the subsetting process.

--xml

Display the TTX XML representation of subsetted font.

Example

Produce a subset containing the characters ‘ !”#$%’ without performing size-reducing optimizations:

$ pyftsubset font.ttf --unicodes="U+0020-0025" \
  --layout-features=* --glyph-names --symbol-cmap --legacy-cmap \
  --notdef-glyph --notdef-outline --recommended-glyphs \
  --name-IDs=* --name-legacy --name-languages=*
class fontTools.subset.Options(**kwargs)[source]

Bases: object

exception OptionError[source]

Bases: Exception

exception UnknownOptionError[source]

Bases: OptionError

set(**kwargs)[source]
parse_opts(argv, ignore_unknown=[])[source]
class fontTools.subset.Subsetter(options=None)[source]

Bases: object

exception SubsettingError[source]

Bases: Exception

exception MissingGlyphsSubsettingError[source]

Bases: SubsettingError

exception MissingUnicodesSubsettingError[source]

Bases: SubsettingError

populate(glyphs=[], gids=[], unicodes=[], text='')[source]
subset(font)[source]
fontTools.subset.load_font(fontFile, options, checkChecksums=0, dontLoadGlyphNames=False, lazy=True)[source]
fontTools.subset.save_font(font, outfile, options)[source]
fontTools.subset.parse_gids(s)[source]
fontTools.subset.parse_glyphs(s)[source]
fontTools.subset.parse_unicodes(s)[source]
fontTools.subset.main(args=None)[source]

OpenType font subsetter and optimizer