Re: Transforming hmtx table

David, thanks for dredging up that document, I couldn't find it myself
because I misspelled it "htmx".

I did consider it, but it seemed like it would add nontrivial complexity to
the decoder, so didn't seem like it would be worth it. The document
outlines some other potential transforms (cmap, etc), but basically in the
tradeoffs between complexity (which includes decode time) and compression I
ended up (after discussion with others in the group) only going after the
biggest wins, which of course turned out to be glyf/loca.

Raph

On Fri, Apr 24, 2015 at 11:25 AM, David Kuettel <kuettel@google.com> wrote:

> 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
>>
>
>