Path: utzoo!attcan!uunet!cs.utexas.edu!wuarchive!julius.cs.uiuc.edu!apple!apple.com!kevina
From: kevina@apple.com (This space for rent)
Newsgroups: comp.lang.postscript
Subject: Re: ATM 2.0/Type 1 question
Message-ID: <10769@goofy.Apple.COM>
Date: 18 Oct 90 16:08:31 GMT
References: <4447@husc6.harvard.edu>
Sender: usenet@Apple.COM
Organization: Apple Computer, Inc.
Lines: 44

In article <4447@husc6.harvard.edu> kenh@hscfsas1.harvard.edu (Ken 
Hancock) writes:
> I recently downloaded a Type 1 Shareware font called Zirkle and have
> noticed a few problems.  The lower-case 'e' is designed as a single
> outline (like a rubber tube wrapped around).  Where the outlines meet,
> there is a bit of an overlap.
>  
> ATM inverts the overlap, and printing the font to any QuickDraw
> printer shows the overlap inverted as well.
>  
> The Personal NT prints the font as one would expect it -- without
> overlap.  This raises a few of my questions:
>  
> 1) Is this just another example of a font which has been incorrectly
>    designed (as is often the case with PD/SW fonts)?
Yep.

> 2) Related to (1) are overlapping areas allowed, or should they
>    be removed and a clockwise outer path and a counterclockwise 
>    inner path substituted?
According to the infamous Black Book (section 3.6), "a single closed 
outline should not intersect itself".  They use a stroked outline as an 
example of why this is a bad thing, but it also messes up on even-odd 
fills.  However, you should replace it with a counterclockwise outer path 
and a clockwise inner path.  (According to section 3.5, "A subpath that is 
to be filled must be defined in a counterclockwise orientation in 
character space.  A subpath that is to be left unfilled must be defined in 
a clockwise orientation.")

> 3) The Personal NT supposedly as the ATM font generation built
>    into the Postscript ROMs, yet ATM 2.0 and the output doesn't
>    match.  Explanation?
ATM 1.x and most (if not all) Level 1 PostScript interpreters use a 
winding-number fill (like the PostScript fill operator).  Rumor has it 
that ATM 2.0 uses a faster even-odd fill (like the PostScript eofill 
operator).  Since the Personal LaserWriter NT came out several months
before ATM 2.0 was released, it's safe to assume that ATM 1.x technology 
is what was included.

Disclaimer:  This is not an official Apple claim about ATM in the Personal 
LaserWriter NT.

--Kevin Andresen [kevina@apple.com]
"Orange whip?  Orange whip?  Three orange whips."