[Gnome-print] Re: [Gimp-print-devel] PS Obsession????

[Robert L Krawitz <rlk alum mit edu>]

   Date: Wed, 07 Jun 2000 21:18:43 +0000
   From: Juantomas Garcia <juantomas@lared.es>

   Michael Sweet wrote:

   > Well, like it or not PostScript is the defacto standard printing
   > language for 90% of all UNIX apps.  This doesn't mean that it is
   > the best solution, just the easiest.

   This's really courious at least. More than 90% percent of the printers in
   the world are not PS.  Mostly PCL* and EPSON*. We don't need to lose
   the point that GNOME proyect is oriented to _every_people_ not just
   the companies with expensives printers (cost of ps printers doubles the
   price of normal ones).

   The choice of the easiest path to support printing in old Unixes is one
   of the mayor lacks of the Unixes applications. I never understand why
   I need to buy or sell a printer to work properly with an app.

The answer is that you don't.  That's what Ghostscript and PPD's are
for.

The notion that the IL has to look anything like the printer's native
language seems to be permeating this discussion.  It's completely
wrong.  For that matter, I doubt that the internal language used by
any PostScript printer really is PostScript; the printer contains a
PostScript interpreter (i. e. a firmware RIP), but the low level
control language for the print head probably looks more like ESCP/2
raster or some such.

The truth is that ESCP/2 Raster is really a microcode language to
support a particular print head and paper feed mechanism.  Its
commands bear no relationship to abstract notions of bitmaps, or
vector drawings, or fonts.  It's purely a hardware control language.
Just read the manuals at http://www.ercipd.com/isv/edr_docs.htm and
that will be plainly obvious.

What's more, there is no one ESCP/2 Raster language.  Each printer has
its own variants.  There are vaguely common themes, but they're
constantly changing to support new, more capable printer mechanisms.
A print file generated for the Stylus Photo EX will not print
correctly, and may not print at all, on a Stylus Photo 870.

It's a lot easier to interpret the high level abstractions of
PostScript, turn them into a (virtual) raster bitmap, and render for
an 870 than it is to take an 870 dump file and generate even a bitmap,
much less any kind of high level abstractions.  One of our developers
wrote just such an unprint program.  It does a reasonable job of
generating a bitmap, but there's certainly no abstract content of said
bitmap.

The idea of using PostScript is to use it as an interchange language,
since it has the right constructs for that purpose (and with PPD
files, it can actually do the right thing for arbitrary printers).

-- 
Robert Krawitz <rlk@alum.mit.edu>      http://www.tiac.net/users/rlk/

Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom -- mail lpf@uunet.uu.net
Project lead for The Gimp Print --  http://gimp-print.sourceforge.net

"Linux doesn't dictate how I work, I dictate how Linux works."
--Eric Crampton