Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!execu!sequoia!rpp386!woody
From: woody@rpp386.cactus.org (Woodrow Baker)
Newsgroups: comp.lang.postscript
Subject: Re: ruler.ps - an inch/point ruler of your very own
Summary: isn't that the truth
Message-ID: <17662@rpp386.cactus.org>
Date: 15 Jan 90 12:59:07 GMT
References: <21772@uflorida.cis.ufl.EDU> <1990Jan14.180821.18711@trigraph.uucp>
Organization: River Parishes Programming, Plano, TX
Lines: 39

In article <1990Jan14.180821.18711@trigraph.uucp>, bruce@trigraph.uucp (Bruce Freeman) writes:
> The great thing about points is that there are so many of them to the inch.
> PostScript has decided that there are exactly 72 to the inch but the industry
> standard is generally that there are 72.3 points to the inch. As a typesetting
Yup, For whatever reason, Adobe definitly decided to thumb it's nose at
the very industry that it was/is trying to bring into the 20th centry.
Methinks that perhaps they wanted to use integers or some such, so they
decided to use integral "point" size.  They certainly, with a tad bit more
effort could have used a scaled binary integer i.e. a fixed point integer
format to do the work , but I can certainly understand why they might
have decided to use 72 points rather than 72.3.
Of course floating point is be fine, but it does
indeed slow things down, and with no FPU in the standard printers, you need
all the speed that you can get.  Actually, you can make your user space be
72.3 if you want to.  consider that 300/72 is 4.1666 pixels per point
and 300/72.3 is 4.14937 pixels per point, you certainly can modify the
scaling matrix to get exactly 72.3 points per inch.  There will still be
the problem with the varying dot boundries.  1/300 inch is .0033333
inches .003333+4.14937 is 4.15270.  If you are using a finer resolution than
1/300th of an inch, it can be made exact.
All in all, the decision to use 72 points per inch probably had it's
roots in some fairly sound reasoning.  I can only hope that it was not
because they decided that they could change a centuries old standard.
I'm sure that we will or I will hear from them on this point, (no pun intended)
but it is indeed a problem.  Remember the language DOES give you a way around it.
g
> where the output is from. It is even more fun when a publisher says I thought
> I told you to make this 35 picas 6 points not 35 picas 8 points (actually at
> this distance the discrepancy is only 0.02" but you get the idea).
The Postscript point ruler that I use all the time, has divisions about
every 2 points. At 300 dpi it is legable enough that I can get measurements
close enough for government work.

cheer
Woody
> 
> Just some of those things that makes typesetting so interesting!
> -- 
> Bruce Freeman	Trigraph Inc., Toronto, Canada		utzoo!trigraph!bruce