🚀 go-pugleaf

Andrew Loewenstern writes

> You're close...  It's "anti-aliasing" and PostScript can't do it.
> PostScript prefers high resolution output devices. (monitors are
> about as low resolution as you can get).

Quite correct.  Anti-aliasing has some tough problems associated
with it that make it extremely difficult to implement in an
interactive display environment.  Most imaging models that do
anti-aliasing either ignore the problems or don't contain an imaging
model rich enough to get you into trouble with anti-aliasing.

With a rich imaging model dedicated to WYSIWYG, the problems of
anti-aliasing can't be ignored, and they can significantly affect
the output in a number of cases.  Also, doing anti-aliasing the
'brain-dead' way (pixel reduction) can lead to some undersireable
effects, such as less readable characters, if it isn't taken into
account very early on in the imaging process.

Also, displays will be making significant jumps in resolution over
the next few years as flat panel displays become consumer items.
Nearly all of the flat panel technologies can have very high
resolutions without hitting significant cost barriers (unlike CRTs).
Over about 150dpi (my estimate), it is more desireable to rasterize
quicker and not play around with things such as anti-aliasing.
Considering the work required to do anti-aliasing properly, is it
really worth it then to make the imaging model do it, or to allow
the application to do it for the few cases where they need it.

To do anti-aliasing within an application, simply rasterize into
an off-screen buffer at a larger size (2 or 4 times as large on a
side, or 8 times as large only horizontally), and then read back
the values to convert that into a useable image of the right size,
maintaining the gray values during the compression.  This is easiest
done with the 8 times horizontal expansion, but character
rasterization might not come out as well in this case.  Note also
that you may get porttions of thin lines dropping out - use real
linewidths instead of 0 when drawing lines into the offscreen
pixmap.  That way they will get expanded properly and should provide
black connectivity.

--
Scott Byer                             NeXTMail: byer@mv.us.adobe.com
Adobe Systems Incorporated               These are *my* opinions, and  
1585 Charleston Road, P.O. Box 7900        do not necessarily reflect
Mountain View, CA 94039-7900             the opinions of my employer.
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