Create WOFF files with Zopfli compression
This is a modified version of the sfnt2woff utility that uses Zopfli as a compression algorithm instead of zlib. This results in compression gains of — on average — 5-8% compared to regular WOFF files. Zopfli generates compressed output that is compatible with regular zlib compression so the resulting WOFF files can be used everywhere.
To create a WOFF file from an OpenType files:
> sfnt2woff-zopfli [-v <maj>.<min>] [-m <metadata.xml>] [-n <iterations>] [-p <private.dat>] <otffile>
-v <maj>.<min> set font version number (major and minor, both integers) -m <metadata.xml> include metadata from <metadata.xml> (not validated) -n <iterations> number of zopfli iterations (default = 15) -p <private.dat> include private data block
To decompress a WOFF file and write the OpenType file to stdout:
> woff2sfnt-zopfli [-v | -m | -p] <woff>
-v write font version to stdout -m write WOFF metadata block to stdout -p write private data block to stdout
To compile the utilities, run make:
This will compile two utilities
sfnt2woff-zopfli to convert OpenType files to WOFF and
woff2sfnt-zopfli to convert WOFF files back to OpenType files. If the build was succesful you can make them available on your system by copying the resulting executables to
/usr/local/bin and making them executable (
The WOFF portion of the code is taken from sfnt2woff, which is licensed under the MPL/GPL/LGPL. The Zopfli implementation is licensed under the Apache License. My modifications to
woff.c are also licensed under the MPL/GPL/LGPL.
You can also use the ttf2woff tool, which also converts OpenType files to WOFF using Zopfli, but is exclusively licensed under the GPL. However it doesn't have a command line option for the number of Zopfli iterations and thus can't create files as small as sfnt2woff-zopfli.