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Re: Webfont compression

From: Laurence Penney <lorp@lorp.org>
Date: Wed, 22 Jul 2009 14:51:36 +0100
Message-Id: <A70675AC-930D-431B-8A8D-B1DBFA943224@lorp.org>
To: www-font <www-font@w3.org>
Thanks a lot for the elucidation on how MTX works. Your "32.6%  
improvement" is a little misleading - the improvement percentage  
should work on the upper figure as a denominator, thus a 24.6%  
improvement. Or, one could say "MTX compression on Georgia is 15.5  
percentage points better than gzip".

Since we're all assuming that subsetting will be widely used (at the  
very least, fonts containing, say, all of WGL4, such as georgia.ttf,  
will probably be rare), then we can infer that in many, perhaps most  
deployments - notably Latin 1 fonts automatically converted from OTF/ 
CFF - the benefits of MTX will be slight.

- L

On 21 Jul 2009, at 17:21, Levantovsky, Vladimir wrote:

> According to your own tests with "Georgia":
> EOT file size created using (ttf2eot + gzip) is 32.6% larger than EOT
> file with MTX compression created by WEFT. Since both gzip and MTX are
> lossless compression techniques, I think that 32.6% improvement  
> could be
> considered significant.
> MTX employs a two-step process where the font data is first optimized
> and then subjected to entropy coding (modified LZCOMP). It is most
> effective for a screen font that contains larger glyph sets and
> significant amount of hint instructions. Since screen fonts require
> hinting and are much more likely to be used on the web, I would  
> consider
> an efficient compression an advantage for web fonts. Plus,
> MTX-compressed font contains separate blocks of font data, which   
> makes
> it possible to implement a progressive font download mechanism where
> metrics and layout information can be used by a UA to layout a web  
> page
> while the glyph data and hints are still being downloaded.
> Also, it has been shown that there are new compression techniques,  
> such
> as LZMA, that produce better results than gzip. It is important to  
> keep
> in mind that even though MTX is originally a part of EOT submission -
> nothing would prevent W3C and Fonts WG to create a new, truly superior
> technology where, for example, parts of MTX (font optimization) can be
> combined with LZMA to produce best possible results. This technology
> could potentially be part of a future .webfont implementation.
> However, having said this - I believe that the major benefit of web  
> font
> initiative would be to come up with a solution that can address the
> largest number of web users in a shortest time possible; a solution  
> that
> would give web authors tools they need today. For this reasons - I  
> think
> that a subset of EOT (either EOT with MTX but without root strings, or
> EOT-lite) would be most pragmatic way to make web fonts a web reality
> today, addressing the large base of IE users.
> Regards,
> Vladimir
Received on Wednesday, 22 July 2009 13:52:12 UTC

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