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From: jfr@locus.com (Jon Rosen)
Newsgroups: comp.lang.postscript
Subject: Re: Doubling Font sizes and Shrinking Photographically
Message-ID: <19458@oolong.la.locus.com>
Date: 13 Nov 90 04:18:04 GMT
References: <17104@shlump.nac.dec.com> <48104@cornell.UUCP>
Organization: Locus Computing Corp, Los Angeles
Lines: 34

In article <48104@cornell.UUCP> wayner@kama.cs.cornell.edu (Peter Wayner) writes:
>>Well, PostScript uses a single "master" (ie, character shape definition) for all
>>point sizes, so you don't actually get different shapes for different  sizes. 
>>Therefore, you can easily take a 300dpi PostScript printout, stat it down, and
>>treat it as 600 dpi.
>
>Does it really? Adobe must produce fonts that are tuned to different
>sizes. Can they be manipulated?
>

Adobe's font sizing method with Postscript is very interesting.  It is true
that the base for all Type 1 fonts is a single set of stroke definitions
that are enlarged and rasterized for any request point size.  This allows
theoretically unlimited sizing of all fonts.  Also, the rasterizing process
is done at the actual Postscript machine's resolution so that the rendering
is optimal for each different type of printer.  However, a strict mathematical
rendering of the font definition in all sizes will not, as anyone familiar
with typography would know, give a good "eyepleasing" typeface.  Type 1
fonts in Adobe Postscript include "hints" which are essentially little
pieces of Postscript code that are attached to each character definition
and which modify the actual raster image depending on the size of the
character, the style and possibly other variables like kerning, leading,
etc.  This means that as you enlarge fonts, you will see small changes
in the actual raster image, mostly in the thickness of the body and stem
elements and in the ascender/descender elements.  This allows Adobe
Type 1 fonts to look much better than simple magnification.  It also
means that sometimes simple overmagnification followed by stat reductions
will not provide as much benefit as would be expected, and in some cases,
may actually be counterproductive.
 
Unfortunately, as far as I can tell, it is not simple to get at the
hint definitions for modification.

Jon Rosen