Note that OT-SVG only allows gzip-wrapper compressed documents, not zlib-wrapped.
On Sat, Jun 8, 2019 at 1:57 AM Moazin Khatri <moazinkha...@gmail.com> wrote: > Hi, > > In OpenType fonts, SVG documents can be either in plain text or gzip > encoded. > > While writing the code to read these documents I looked for a function > which could do gzip decoding inside FreeType. That's when I found > `FT_Gzip_Uncompress'. Using it, I realized it didn't work as expected and > returned errors. > > After using zlib in a separate program on the same data I figured out the > problem. Zlib data can be encoded with both `gzip' and `zlib' encoded > wrapper. AFAIK, by default, it looks for only `zlib' wrapper. The current > call to `inflateInit2' is: > > 749| err = inflateInit2( &stream, MAX_WBITS ); >> >> > `MAX_WBITS' is 15. Thus, it only looks for `zlib' wrapper and in case of > gzip compressed SVGs, returns error when `inflate' is called. The fix is to > replace it with: > > 749| err = inflateInit2( &stream, MAX_WBITS|32 ); >> >> > This enables both `gzip' and `zlib' decoding with automatic header > detection. Solving my problem. > > I am quoting the relevant section from zlib's manual for reference. Can be > seen here <https://www.zlib.net/manual.html>: > > windowBits can also be greater than 15 for optional gzip decoding. Add 32 >> to windowBits to enable zlib and gzip decoding with automatic header >> detection, or add 16 to decode only the gzip format (the zlib format will >> return a Z_DATA_ERROR). > > > This solves it for me and I HOPE this won't cause cause any previous code > relying on `FT_Gzip_Uncompress' to fail. Let me know if there are easy > tests to check that. > > Let me know if this is the right change and can also be made in master > later on, meaning I can rely on it. :) > > Moazin > > > _______________________________________________ > Freetype-devel mailing list > Freetype-devel@nongnu.org > https://lists.nongnu.org/mailman/listinfo/freetype-devel > -- behdad http://behdad.org/
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