Re: [Gimp-print-devel] More stuff

[Robert L K. <rl...@al...>]

   Date: Thu, 04 May 2000 16:11:01 +0200
   From: Ron van Ostayen <R.A...@Wb...>

   > One pass, and bidirectional.

   Now I'm confused.  The printer head goes across the page dumping ink,
   and returns dumping ink.  Then the paper is moved forward approx. 1.4cm.

Hmm.  I see what you mean.  At 360 dpi, the 900 prints *every* row.
In theory, at any rate.

   I would call this 2-pass, bidirectional?

   The windows driver uses a mixed approach:  When color is needed it uses
   the same approach as gimp-print but when (black) text or figures are
   printed then the head goes across the page dumping ink, the
   paper is moved forward 1.4cm, the head returns dumping ink, and the
   paper is moved forward approx. 1.4cm.

   I would call this 1-pass, bidirectional?

OK, I think I have a clue what's going on here.

You'll find this in print-escp2.c:

  if (use_glossy_film)
    dither_set_black_upper(dither, 1.0);
  else
    dither_set_black_upper(dither, 1.0);

Try changing the 1.0 to .99 (make it less than one by greater than one
part in 65536).  See if that makes a difference.  What *may* account
for your problem is that even in pure black regions the driver's
dropping some color ink.  If that doesn't work, try printing something
with -dColor=0 as a test.  This will print black ink only.

   Furthermore the windows driver uses a much faster method of paper
   transport across empty areas.  The gimp-print driver is very slow across
   empty areas.

I know.  I've partially optimized it, but not completely.  That
shouldn't be all that hard to get right.  It's possible that what
looks empty isn't entirely, but it's possible to figure that out from
the print file, if what I eventually do to fix it doesn't solve the
problem.

   And yet the windows printer dump file size is about 2x as large.

Now that's very interesting.  I wonder why.

   During rendering the difference is a more pronounced: Printing 10 pages
   of my report to file takes about 20s in windows and 220s in gimp-print!!

Yeah, the dithering still needs some performance tuning...

   The quality of in particular the windows text is much better than the
   gimp-print output.  Figures and photos are comparable.

What's the difference (more specifically)?

-- 
Robert Krawitz <rl...@al...>      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 lp...@uu...
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