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From: brown@vidiot.UUCP (Vidiot)
Newsgroups: comp.lang.postscript
Subject: Re: Apple LaserWriter IINT and setscreen
Message-ID: <1480@vidiot.UUCP>
Date: 10 Mar 91 03:56:44 GMT
References: <1453@vidiot.UUCP> <12443@goofy.Apple.COM>
Reply-To: brown@vidiot.UUCP (Vidiot)
Organization: Vidiot's Hangout
Lines: 31

In article <12443@goofy.Apple.COM> kevina@apple.com (Nobody you know) writes:
<In article <1453@vidiot.UUCP> brown@vidiot.UUCP (Vidiot) writes:
<> Would some kind soul please explain why the dot frequency values between
<> 47.1405 and 60.6091 (inclusive) result in a frequency of 60.0 being used
<> internally?  The angle for this to occur is 45 degrees.
<> 
<> I did a little test program that does a set screen and then turn right 
<around
<> and do a currentscreen to print what the printer is using.
<> 
<> If the angle is 35 degrees, the test goes right through 60 without a 
<problem.
<> This is using an increment to the frequency of .01 and starting at 59.0.
<
<[Fun fact to know and yell: not only will frequency values from 47.1405 to 
<60.6091 result in the same internal frequency, as you have discovered, but 
<it is 53 degrees, not 60!]

Do you mean 45 degress instead of 60?

<Good references for all this are the new Red Book, "Digital Halftoning" by 
<Ulichney, and part III of "Real World PostScript" edited by Roth.

I had the "Real World PostScript" under my nose and never even noticed.
Thanks the pointer.  I'm going to look at the book now.

The new Red Book, left alot to be desired in this department.
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