[Desktop_printing] Smooth dithering

Robert L Krawitz rlk at alum.mit.edu
Fri Feb 17 04:21:06 PST 2006

   Date: Fri, 17 Feb 2006 08:23:56 +0100 (CET)
   From: Kai-Uwe Behrmann <ku.b at gmx.de>

   preparing a comparision between a standard prepress RIP and an open
   source PDF workflow for a Linux fair in Germany I have some
   trouble. Shurely the partipicants of this list have enough inside
   to cope with the issues.

   The PDF side seems ok with Ghostscript/CUPS for rendering and
   CinePaint and lcms for displaying. The test runs with the Altona
   Testsuite, a PDF/X-3 collection from ECI/UGRA/FOGRA.

   The dithering of the propriarity driver is much smoother than
   Gutenprint's. The inkjet used is a Epson 3000. The device does 720
   dpi at a fixed drop size.  Now comparing the propriarity driver
   output with Gutenprint's rendering shows much more noice peaks in
   the Gutenprint dithering. It seems that Gutenprint puts drops not
   so very well wighted. This is the case for b/w and for colour
   printing. The dithering is clearly a minus in the side by side

   One problem seems to be in not taking the other colour planes into
   account. So for instance a black drop is too often placed next to a
   cyan one. Instead, as seen in the propriarity dithering, yellow can
   be placed near to black and cyan. Black and cyan should have the
   most distances followed by magenta and yellow. There is no such
   hierarchy obvious in Gutenprint's dithering results.

I tried a variant of EvenTone dithering, which I called UniTone, for a
while.  It worked fairly well in this regard, but I never got it quite
right.  This is clearly something we could improve on.

I believe that the latest version of EvenTone dithering that Raph
Levien has released can do this; I just haven't had time to study the
code and implement it.  This is very much something I want to do; if
anyone has the time to volunteer for this it would get it done a lot

Robert Krawitz                                     <rlk at alum.mit.edu>

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

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

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