Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!rutgers!apple!jp
From: jp@Apple.COM (John Peterson)
Newsgroups: comp.graphics
Subject: Re: Gray-scale antialiasing (yes, it can work)
Summary: Yes, anti-aliased fonts really work.
Keywords: anti-aliasing text
Message-ID: <19809@apple.Apple.COM>
Date: 1 Nov 88 19:35:32 GMT
References: <74013@sun.uucp> <148@internal.Apple.COM> <4763@mnetor.UUCP> <174@internal.Apple.COM>
Organization: Apple Computer Inc., Cupertino, CA
Lines: 44

>>I am constantly amazed that anti-aliased text has not become the norm.
>>It works (very well).  It is cheap to implement (cheaper than raising
>>the pixel resolution of the display).
> 
> As to how well it works, the jury is still out.  In spite of the enthusiasm
> of its supporters, the question of the *readability* of anti-aliased text
> remains open.

Not really, some studies have been done.  I have in front of me a paper
titled "CRT Typeface Design and Evaluation" that was prepared by some people
at MIT and IBM.  In their study they found that people can read a display
with anti-aliased fonts -faster- than the equivalent hardcopy text.  This
compares quite well to traditional CRT text, which was found consistantly
slower than hardcopy.

> As to its being cheap to implement, it's true there is less hardware cost
> in anti-aliasing than there is in greater pixel density.  But until someone
> makes a breakthrough or two, it requires some very intense computation
> right where you don't want it, i.e. right in the middle of your character-
> display loop where it trashes your display performance.

This is incorrect.  I would not consider BitBlt (aka CopyBits) to be an
"intense computation."  Like all other screen fonts, anti-aliased fonts are
pre-computed and cached.  To display them, you copy rectangles of pixels onto
the screen.  For the vast majority of applications (page layout, word 
processing, etc) that's all the "computation" you need to do.  

The only case where more work is needed is when you're drawing anti-aliased
characters over an arbitrary background image - then you need to do some
work to blend edges of the characters with the background (a multiply,
shift, add - still not "intense").  However, in this case text is usually
displayed in small quantities (as annotations of the image) and isn't the
bottleneck.

> It looks to me like anti-aliasing is about where OCR was until recently: it
> sounds like a great idea, everyone wants it, and lots of people will tell
> you it's here, but it isn't.

Take a look at the closing credits of Apple's SIGGRAPH video, "Pencil Test".
They look pretty good... 

> David Casseres

John Peterson
(jp@apple.com)