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From: karl@apple-gunkies.gnu.ai.mit.edu (Karl Berry)
Newsgroups: comp.text.tex
Subject: Re: Can character "coloring" be altered within TeX?
Message-ID: <KARL.91Mar28184135@apple-gunkies.gnu.ai.mit.edu>
Date: 28 Mar 91 23:41:35 GMT
References: <1991Mar26.233116.26641@rodan.acs.syr.edu>
	<1991Mar28.163342.22523@csrd.uiuc.edu>
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In-reply-to: eijkhout@s41.csrd.uiuc.edu's message of 28 Mar 91 16:33:42 GMT

>> The closest parameter is the \sfcode table, but I
>>cannot find any mechanism whereby all of the entries may be quickly changed
>>by a uniform factor.  Currently I am kerning each and every character to
>>obtain the correct spacing.  Is there any better solution?

>Sorry to say that what you want is indeed a component of
>high quality typesetting systems, but not of TeX, as yet.

Victor, I disagree with the implication of `high quality' here.  I think
it is an abomination that typesetter manufacturers ever provided the
``feature'' of being able to change the letter spacing.

One of the basic elements of any well-design type is that the distance
between the main vertical strokes is close to a constant.  There are
good physical reasons why this is true (the human visual systems sees
certain frequencies much better than others; the spatial frequency of
the strokes in typical 10pt type ``just happens'' to be one the hvs is
highly attuned to).  When you allow arbitrary munging of the
intercharacter spacing, you allow the side bearings to be changed
without also changing the interior spaces, creating, in my opinion,
trash.

As for the ``as yet'', here is what Knuth has to say (the very last lines of
tex82.bug):

. if anybody wants letter spacing desperately they should put it in their own
   private version (e.g. generalize the hpack routine) and NOT call it TeX.)
   

All that said, you can do letter spacing fairly easily in PostScript; I
think it might even be in the cookbook.

karl@cs.umb.edu