Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!decwrl!adobe!heaven!heaven.woodside.ca.us
From: glenn@heaven.woodside.ca.us (Glenn Reid)
Newsgroups: comp.sys.next
Subject: Re: Questions about Adobe fonts
Message-ID: <522@heaven.woodside.ca.us>
Date: 11 Jun 91 07:35:20 GMT
References: <1991Jun9.152516.18035@ux1.cso.uiuc.edu>
Sender: glenn@heaven.woodside.ca.us
Lines: 44

J.B. Nicholson writes
> I was wondering why anyone bothers publishing "sizes" of scalable fonts
> if the whole point in having this type of font is that they are "stretchable"
> without losing quality.
> 
> If you've got the formula (or whatever) to generate a single character, can't
> you just plug different numbers for sizes in to get different sizes out?
> Thus never needing to go to bitmapped fonts again?
> 
> I know this isn't a technical way of describing it, but it just seems logical
> to me that if you've got a stretchable font like these proportional fonts are
> then you shouldn't need more than one file to describe the whole font (the
> descriptions for every character that that font can do are in that one file).

Well, you're right, in principle.  With a scalable outline font, you don't
need any bitmap screen fonts.  In fact, on the NeXT you can delete all the
bitmap fonts and the outlines work just fine.

However, there are advantages to having the bitmap fonts for small sizes.
Although outline descriptions are very good, there is a point where you
simply run out of pixels, and scan-converting algorithms have to do a lot
of dancing to try to render a complex letterform with four or six pixels
vertically and three or four pixels horizontally, which happens at point
sizes of 8 to 10 points on a typical screen display.  So, the bitmaps are
edited by hand, by human beings, to help the software out a little bit.

But more importantly, the widths of the individual characters have to be
rounded off to the nearest pixel on the screen, which can lead to some
inaccurate character placement and line display as this error is accumulated
across a line of type.  With the hand-tuned bitmaps, some care is taken to
distribute the round-off error evenly across the characters, making some
of the letters round one way, and some the other, in such a way that the
average line length comes pretty close to being accurate, statistically
speaking.

So yes, you're right that they're not really needed, but they do have some
advantages, and they are still built for all known screen display systems,
even when they're not strictly necessary.  The NeXT fonts come with 10, 12,
14, 18, and 24-point screen fonts.  I think the Mac and PC fonts are the same.

--
 Glenn Reid				RightBrain Software
 glenn@heaven.woodside.ca.us		NeXT/PostScript developers
 ..{adobe,next}!heaven!glenn		415-326-2974 (NeXTfax 326-2977)