Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!uunet!mcsun!hp4nl!alchemy!piet
From: piet@cs.ruu.nl (Piet van Oostrum)
Newsgroups: comp.lang.postscript
Subject: Re: Obliquing fonts
Keywords: Oblique, slant, tan
Message-ID: <1991May23.140358.23521@cs.ruu.nl>
Date: 23 May 91 14:03:58 GMT
References: <24968@well.sf.ca.us> <1991May23.092143.14619@nntp-server.caltech.edu>
Sender: piet@cs.ruu.nl (Piet van Oostrum)
Reply-To: piet@cs.ruu.nl (Piet van Oostrum)
Organization: Dept of Computer Science, Utrecht University, The Netherlands
Lines: 40
In-Reply-To: carl@hamlet.caltech.edu (Lydick, Carl)

>>>>> carl@hamlet.caltech.edu (Lydick, Carl) (LC) writes:

LC> In article <24968@well.sf.ca.us>, capslock@well.sf.ca.us (Allen Crider) writes...
>I'm trying to oblique a roman font. I know the pointsize and I know the 
>obliquing angle. The only example of obliquing type I have seen is in
>the Blue book (Tutorial and Cookbook) in which they give an example of
>a font obliqued 30 degrees:
> [12 0 6.93 12 0 0] makefont
> "The 6.93 in our last matrix above is the product of 12xtan30, so our
>characters are obliqued by thirty degrees." Says the Blue Book.
> 
>I tried doing this in C:
>f = 12 * tan(30);
> 
>and get 76.864, not 6.93.
>Since I wasn't around when they passed out the trigonometry, maybe some
>kind soul could guide me to the best way to figure out the correct value
>to put in that matrix. Thanks

LC> PostScript uses degrees.  C's tan() uses radians.  Tan(30 degrees) = 1/sqrt(3),
LC> which is, in fact, about 6.93.

Well, nitpicking: It is 6.93 after multiplying by 12:

Emacs Calc Mode v1.07 by Dave Gillespie
     30
 tan 0.57735026919
     12
   * 6.92820323028

Moreover he gave tan an int, whereas it needs a double (apparently he used
no ANSI style prototypes) so the result was very much implementation
dependent.

Just using a calculator would have been easier.
-- 
Piet* van Oostrum, Dept of Computer Science, Utrecht University,
Padualaan 14, P.O. Box 80.089, 3508 TB Utrecht, The Netherlands.
Telephone: +31 30 531806   Uucp:   uunet!mcsun!ruuinf!piet
Telefax:   +31 30 513791   Internet:  piet@cs.ruu.nl   (*`Pete')