Re: CFF table processing for WOFF2?

Thanks Ken.  Jungshik already tried some of these (original,
desubroutinized, desubroutinized and resubroutinized using our internal
subroutinizer [that I'll open source soon] / otf, woff, woff2) a couple
subsets of Noto.  Jungshik, can you please share your findings?

b

On Fri, Apr 24, 2015 at 8:40 AM, Ken Lunde <lunde@adobe.com> wrote:

> Behdad,
>
> I suggest that you start by using the "Source" fonts that we make
> available on GitHub, specifically the Source Han Sans (though you can
> instead use Noto Sans CJK because their CFFs are identical in terms of the
> actual glyph data), Source Sans Pro, Source Serif Pro, and Source Code Pro
> families. This should be enough to provide preliminary results across a
> variety of glyph sets to determine whether further investigation, which
> would include a larger corpus of OpenType/CFF fonts, has any merit.
>
> Regards...
>
> -- Ken
>
> > On Apr 24, 2015, at 1:03 AM, Behdad Esfahbod <behdad@google.com> wrote:
> >
> > Thanks Ken and Vlad.
> >
> > The first step would be to get a good corpus of CFF fonts.  After that,
> we have all the bits and pieces to try.  There are quite a few combinations
> (~10 to 20), but that's doable in a couple of weeks I would say, assuming I
> can get help from Jungshik and Rod.
> >
> > So, Ken, Vlad, which one of you can contribute a CFF corpus for testing
> purposes for this project?
> >
> > Cheers,
> >
> > behdad
> >
> > On Thu, Apr 23, 2015 at 6:47 AM, Levantovsky, Vladimir <
> Vladimir.Levantovsky@monotype.com> wrote:
> > I think that this is definitely something we need to investigate, and we
> need to do it soon (as in "now"). The WOFF2 spec is still a working draft
> so it is not unreasonable to expect it to be changed (sometimes
> dramatically, as was the case with e.g. layout feature support in CSS
> Fonts), and the changes like this one won't really put anything in jeopardy
> - the existing WOFF2 fonts will work fine while the spec and CTS evolve,
> and the implementations will eventually be updated.
> >
> > If there are significant gains to be realized due to CFF preprocessing
> we ought to consider it but, as Jonathan mentioned, the final decision will
> depend on the tradeoffs between potential benefits of reducing the
> compressed size vs. possible increase of the uncompressed font size.
> >
> > Behdad, how long do you think it would take for you to get at least a
> rough estimates of compression gains and CFF size increase due to
> de-subroutinization?
> >
> > Thank you,
> > Vlad
> >
> >
> > -----Original Message-----
> > From: Jonathan Kew [mailto:jfkthame@gmail.com]
> > Sent: Thursday, April 23, 2015 2:16 AM
> > To: Behdad Esfahbod; WOFF Working Group
> > Cc: Ken Lunde; Jungshik Shin
> > Subject: Re: CFF table processing for WOFF2?
> >
> > On 23/4/15 02:03, Behdad Esfahbod wrote:
> > > Hi,
> > >
> > > Is the working group open to adding processed CFF table to WOFF2 or is
> > > it too late?  Maybe we can do that in a compatible way?
> > >
> > > There's already rumour on the net (which we have anecdotically
> > > confirmed) that CFF fonts compress better in WOFF2 if desubroutinized.
> > > It's unintuitive but makes some sense, if Brotli is great at capturing
> > > redundancy, it should perform at least as well as the subroutinization.
> >
> > This is an interesting possibility, but I do have a concern... unless
> the decoder can "re-subroutinize" the font (which seems like it would add
> substantial complexity to the decoder) this has the potential to
> significantly increase the in-memory footprint of the decoded font. For
> memory-constrained devices, that might be a poor tradeoff.
> >
> > (I have no actual statistics to support or deny this. Both the potential
> savings of compressed size and the resulting change to the uncompressed
> size would be interesting to know...)
> >
> > >
> > > I have only one transform on top of that in mind right now: drop the
> > > offsets to charstrings.  At reconstruction time, split charstring array
> > > on endchar.
> > >
> > > If there is interest I can prototype it and report savings.
> > >
> > > Cheers,
> > >
> > > behdad
> >
> >
> >
>
>