Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!menudo.uh.edu!nuchat!shell!leo!lee
From: lee@leo (Bill Lee)
Newsgroups: comp.lang.postscript
Subject: Re: Obliquing fonts
Keywords: Oblique, slant, tan
Message-ID: <1991May28.131731.24518@shell.shell.com>
Date: 28 May 91 13:17:31 GMT
References: <24968@well.sf.ca.us>
Sender: usenet@shell.shell.com (USENET News System)
Organization: Shell Oil
Lines: 40

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

Here's a procedure that I use to achieve just what you're looking for.

Bill Lee		lee@shell.com
Shell Oil Co.

-------------------------cut here--------------------------------------------
%* _________________________ Oblique __________________________________________
%* Procedure to modify the (normally) rectangular coordinate system of the
%* page to a non-right angle. When used, all x and y dimensions are
%* measured parallel to the new x and y axese. This results in squares
%* becoming parallelograms, circles becoming ellipses, etc. It also means that
%* moving off into the page will often run off the edge of the paper, so
%* be careful of the positining on the page.
%*
%*	angle Oblique
%*		where angle is the off-vertical of the Y axis in degrees.
%*		A positive angle is clockwise rotation of the Y axis 
%*		relative to existing axis.

/Oblique {
  /angle exch def
  [ 1 0 angle sin angle cos 0 0 ] concat
  } def