Re: Transforming hmtx table

On Fri, Apr 24, 2015 at 8:56 AM, Levantovsky, Vladimir <
Vladimir.Levantovsky@monotype.com> wrote:

>  Hi Behdad,
>
>
>
> The original MTX had pre-processing steps defined for hdmx and vdmx tables
> but I don’t think we did anything with hmtx. I remember Raph ran an
> estimate and concluded that hdmx/vdmx processing had ‘unfavorable’ gain
> /complexity ratio contributing little to overall compression so we decided
> to not have it as part of WOFF2 pre-processing step. I am not sure if we
> evaluated hmtx pre-processing at the same time, may be Raph can help to
> remember what, if anything, we considered w.r.t. hmtx table.
>

Here for reference is a copy of the document that Raph originally wrote,
which captured the various optimization explorations:

http://wiki.font-compression-reference.googlecode.com/git/img/WOFFUltraCondensed.pdf

There is a section on the related hdmx table, which Raph recommended either
just compressing or stripping altogether.

>
>
> Cheers,
>
> Vlad
>
>
>
>
>
> *From:* Behdad Esfahbod [mailto:behdad@google.com]
> *Sent:* Friday, April 24, 2015 2:30 AM
> *To:* WOFF Working Group
> *Subject:* Transforming hmtx table
>
>
>
> Hi,
>
>
>
> Has the working group considered transforming the hmtx table to remove the
> lsb field completely, if the lsb is the same as the xMin from glyf table
> for all glyphs?  That will save two bytes per glyph for TrueType fonts
> before Brotli compression.
>
>
>
> behdad
>