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GIMPPRINT-DITHERS(7)		     Gimp-Print Manual Pages		     GIMPPRINT-DITHERS(7)

       gimpprint-dithers - Gimp-Print dither algorithms

       Gimp-Print  includes  several  dither algorithms.  Dithering attempts to reproduce various
       shades of gray (or all colors) from only a few different inks (black, cyan, magenta,  yel-
       low, and sometimes light cyan and light magenta).  The dots can't vary in darkness or size
       (except for certain special printers), and so we need to lay down a  certain  fraction  of
       dots  to represent each distinct level.	Different dither algorithms are suited to differ-
       ent purposes, and some are significantly faster than others.

       Dither Algorithm   Description
       Adaptive 	  Adaptive Hybrid
       EvenTone 	  EvenTone screening (experimental)
       Ordered		  Ordered
       Fast		  Fast
       VeryFast 	  Very Fast
       Floyd		  Hybrid Floyd-Steinberg

       For the highest quality, we recommend use of Adaptive Hybrid  dithering.   For  continuous
       tone  images, Ordered works just as well and is somewhat faster.  Ordered dithering yields
       noticeably inferior results with text and intricate line art, particularly at high resolu-

       EvenTone  dithering is a relatively new screening technology developed by Raph Levien.  It
       offers superior smoothness in highlights and midtones, and increased accuracy in  shadows,
       resulting  in  significantly  improved results overall.	The version of EvenTone dithering
       that we are using is enhanced with some additional improvements we  have  made.	 It  cur-
       rently  only  operates  with  CMYK (4, 6, or 7 color output) with RGB input, and should be
       considered experimental.  Note that it is patented (see US  patent  5917614),  but  it  is
       licensed  for  use  with  GPL  software.   See http://www.levien.com/patents.html for more

       Fast dithering, which is a simplified version of ordered dither, is significantly  faster,
       but color accuracy is worse, particularly on six color printers and printer using variable
       dot sizes.  On simple four color printers, the quality is quite reasonable, although color
       printing  will show more speckling in dark tones than Ordered dither.  For single dot size
       printers, printing grayscale, this algorithm yields almost identical  results  to  Ordered
       with  some  performance	improvement.  On three color printers, the results should be very
       similar to Ordered.

       Very Fast is even faster than Fast, with even more loss of quality.  It	shows  even  more
       speckling,  and	the output is heavily patterned.  On laser printers, and possibly on cer-
       tain kinds of text and line art, Very Fast dithering may actually yield the best quality.

       Error diffusion algorithms (Hybrid Floyd-Steinberg is such an algorithm) perform very well
       at  high  densities,  and are capable of rendering very fine detail well, but they tend to
       exhibit artifacts in the form of "waves" or "worms" of dots which  results  in  noticeable
       texturing  in  pale  areas.   Furthermore, pale areas immediately adjacent to white take a
       while to "build up" sufficient error to print at all.  This is sometimes called "tearing".
       Its use is not recommended.

       Copyright (C) 2001 Michael Sweet (mike@easysw.com) and Robert Krawitz (rlk@alum.mit.edu)

       This program is free software; you can redistribute it and/or modify it under the terms of
       the GNU General Public License as published by the Free Software Foundation;  either  ver-
       sion 2 of the License, or (at your option) any later version.

       This manual page was written by Roger Leigh (roger@whinlatter.uklinux.net)

       gimpprint-color(7),   gimpprint-imagetypes(7),	gimpprint-inktypes(7),	 gimpprint-media-
       sizes(7), gimpprint-mediasources(7), gimpprint-mediatypes(7),  gimpprint-models(7),  gimp-

Version 4.2.4				   25 Nov 2002			     GIMPPRINT-DITHERS(7)
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