🚀 go-pugleaf

jkimball@src.honeywell.com (John Kimball) writes:

>Apologies if this is a FAQ ...

It's a FOP --- Frequently Occuring Problem :)

>I'm in several groups that periodically exchange documents by email.  Most
>people have started exchanging Postscript -- so that the text is typeset,
>so that figures can be included, etc.

Completely reasonable.

>But -- it seems that if more than three or so different sites send
>Postscript files to each other, at least one of those files won't work
>on the printers or viewers at the some of the other sites.  Typically one
>or more of the Postscript files will fail to print/display, or will lock up
>printers, or crash viewers, at some random subset of the recipients.
>Meanwhile, the errant file works fine at the sender's site (though the
>sender is probably having trouble with some file from another site).

>There doesn't seem to be anything like "portable Postscript" -- a
>Postscript file seems to be like a tape written on a poorly-adjusted
>tapedrive, which is readable by that drive but no other.  It's a roll of
>the dice whether you'll be able to look at a file you get from some other
>site.

>Is this considered acceptable behavior in the Postscript community?

Not by me!

>If not, is there some way to judge if a given file is "portable Postscript",
>or are there Postscript implementations which are notorious for failing to
>interoperate (and should thus be avoided)?

There are two bottlenecks:

	1. The PostScript code itself
	2. The PostScript interpreter (executing the code)


1. The PostScript code itself
-----------------------------
Adobe has given the computer users community a clear and detailed
specification of the PostScript language (the Red Book).
Unfortunately, many PostScript writers don't comply to those
specifications. Furthermore, they test their code on *one* printer
(two maybe) and then release the code to the world.  I could give
many examples of bad (unportable) PostScript, but that would get
too detailed within the context.

Another point is that in some circumstances writing portable PostScript
is impossible. Think of bitmap fonts for example (TeX), which are tuned
for a specific resolution.

The best way to judge whether a piece of PostScript code is
portable is to test it on at least 5 different PostScript printers.


2. The PostScript interpreter
-----------------------------
After a lot of experience with many different printers I can only
conclude that the only real PostScript compatible printers are the
ones with an Adobe interpreter in it.  All manufacturers who wrote
their own PostScript clone are incompatible in one way or the other.
But also the Adobe interpreters can be incompatible. Think of
resolution and available fonts for example.

The best way to judge whether a printer is reasonable standard
is to send it some test files. Maybe a useful way to spend some
time is to develop a test which will test a printer (or more general:
PostScript device) on all kind of famous incompatibilities.
The problem is that each new printer on the market will introduce
new incompatibilities.

Jan van der Steen
-- 
    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
     Jan van der Steen                 jansteen@cwi.nl
     Centre for Mathematics and Computer Science (CWI)
     Kruislaan 413, 1098 SJ Amsterdam, The Netherlands