Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!pasteur!helios.ee.lbl.gov!nosc!humu!uhccux!munnari.oz.au!basser!jaa
From: jaa@basser.oz (James Ashton)
Newsgroups: comp.lang.postscript
Subject: Re: Why are postscript fonts so tight?
Summary: No kerning
Message-ID: <2285@basser.oz>
Date: 28 Jun 89 06:26:18 GMT
References: <1974@bunyip.cc.uq.OZ>
Followup-To: comp.lang.postscript
Organization: Dept of Comp Sci, Uni of Sydney, Australia
Lines: 25

In article <1974@bunyip.cc.uq.OZ> greg@brolga.cc.uq.oz (Gregory R. Lehmann) writes:
>It seems to me adobe have made a mistake with their fonts. They all
>have an extremely annoying tendency to run together. The classic
>example is burn which turns into bum ...
>... Any other theories?

The main reason is that PostScript does no kerning.  Each character has
a width and is printed using its width all the time in ignorance of
the adjoining characters.  Characters like `r' (and `j') are a problem
with this system because they are lop sided.  Obviously their widths
have been slightly reduced so that in general they will look alright.
When they adjoin certain other characters however, they practically touch
which is a real bummer in this case (candidate worst pun of the year
here).  The solution is either to store a 2D array of inter character
spaces or to calculate the spacing at typesetting time.  These
alternatives are expensive either in memory or processing time although
a combination involving caching might not be too bad.  The process of
adjusting character separations to account for their shape and not
just their width is called kerning and is particularly important
for poster style art work.  A final note for the pedants lurking in
netland:  it's not really PostScript that is at fault here, only its
font dictionaries and associated machinery.  It would be quite possible
to implement kerning in PostScript with sufficient printer resources.

						James Ashton.