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font scaling (was: Re: Using Computer Modern in Lout - some final questi
From: |
Vadim Nasardinov |
Subject: |
font scaling (was: Re: Using Computer Modern in Lout - some final questions) |
Date: |
Sat, 30 Aug 2008 09:13:00 -0400 |
User-agent: |
KMail/1.9.9 |
On Thursday 28 August 2008 12:20:51 am Clint Olsen wrote:
> > By the time you have converted your font to an AFM file, it is no
> > longer a 10p font. The AFM format describes the abstract shapes
> > of the glyphs without specifying any particular font size. There
> > is a convention that a length of 1000 in the AFM file represents
> > the font size; but it does not represent any *particular* font
> > size.
>
> Ok, so why then do they bother creating all these various AFM files
> corresponding to different sizes from Metafont? Is it because the
> font characteristics don't scale optically and vary with different
> sizes?
Correct.
To lift a couple of quotes...
A Plain TeX Primer, by Malcolm Clark
http://www.amazon.com/Plain-TEX-Primer-Malcolm-Clark/dp/0198537247/
p.32:
| ... These are all 10 point sizes. What does that mean? One way to
| create typefaces is with reference to a `design size'. Or put
| another way, this particular font was designed to be seen at a
| particular size. Had the designer been concerned to have the
| typeface used at a different size, she or he would have designed
| another face, more suited to that particular size. This is a
| somewhat idealized viewpoint. At a practical level, designers
| sometime create typefaces which may be `the same' over a range of
| sizes, designing perhaps four or five subtly different designs to
| cover a typical range from 4pt to 72pt or bigger. The real purist
| would argue that even two faces 1 point different in size ought to
| be designed differently. But life is too short. Some typefaces
| are merely magnified over their entire range. This is probably an
| oversimplification, but for many reasons it is a solution popular
| with the manufacturers of typesetting equipment. TeX adopts both
| solutions, as we shall see later...
TeX for the Impatient, by Abrahams, Berry, and Hargreaves [1990]
(ISBN: 0-201-51375-7)
http://www.tug.org/texlive/Contents/live/texmf-doc/doc/english/impatient/book.pdf
p. 54:
| Fonts can be provided either as outlines or as bitmaps. An outline
| font describes the shapes of the characters, while a bitmap font
| specifies each pixel (dot) that makes up each character. A font
| outline can be used to generate many different sizes of the same
| font. The Metafont program that's associated with TEX provides a
| particularly powerful way of generating bitmap fonts, but it's not
| the only way.
|
| The fact that a single outline can generate a great range of point
| sizes for a font tempts many vendors of digital typefaces to
| provide just one set of outlines for a typeface such as Palatino
| Roman. This may be a sensible economic decision, but it is an
| aesthetic sacrifice. Fonts cannot be scaled up and down linearly
| without loss of quality. Larger sizes of letters should not, in
| general, have the same proportions as smaller sizes; they just
| don't look right. For example, a font that's linearly scaled down
| will tend to have too little space between strokes, and its
| x-height will be too small.
|
| A type designer can compensate for these changes by providing
| different outlines for different point sizes, but it's necessary to
| go to the expense of designing these different outlines. One of the
| great advantages of Metafont is that it's possible to parameterize
| the descriptions of characters in a font. Metafont can then
| maintain the typographical quality of characters over a range of
| point sizes by adjusting the character shapes accordingly.