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Re: ascender, descender, cap-height and x-height

From: Jelle Bosma <jelleb@euronet.nl>
Date: Wed, 26 Jan 2000 09:13:31 +0100
To: "Erik van der Poel" <erik@netscape.com>, <www-font@w3.org>
Message-ID: <01bf67d5$3ba160b0$64646464@jel-nt.jelle.com>

-----Oorspronkelijk bericht-----
Van: Erik van der Poel <erik@netscape.com>
Aan: www-font@w3.org <www-font@w3.org>
Datum: dinsdag 25 januari 2000 23:11
Onderwerp: Re: ascender, descender, cap-height and x-height

>So, if the actual glyphs have such a loose relationship with the em
>square, and font size is defined in terms of em square, then
>font-size-adjust becomes ill-defined too, since aspect is defined in
>terms of font size (and x-height).
>I think the font size should be the sum of the "nominal" ascender and
>the nominal descender for fonts with upper and lower case letters, and
>some other nominal value for other fonts. That's why I'd like to know
>whether I can reliably determine ascender, descender and x-height, and
>how to do that.

It is the type designer who decides on how large the font
is in the EM square. There are no rules. In TrueType
(and OpenType) you can get some measurements such
as the Typographic ascend and descend as explained by Greg.
These values are in the OS/2 table of the font.
In Monotype fonts these are set to top f and bottom g
for the font family. Whether fonts of other foundries
contain reliable values I am not sure. Many foundries didn't
bother much about these things until recently.

Jelle Bosma
Agfa Monotype
Received on Wednesday, 26 January 2000 03:15:17 UTC

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