[Openicc] Introduction / Gutenprint

[Robert L Krawitz]

   Date: Sun, 10 Apr 2005 21:47:24 +0200
   From: Gerhard Fuernkranz <nospam456 at gmx.de>

   Kai-Uwe Behrmann schrieb:

   >The concretisation from a simple to a full separated or complex
   >colour space could allways be possible. This allowing: CMYK ->
   >CcMmYK, while the linearistation can be done optionally with CMYK
   >or CcMmYK curve profiles.

   What I want to say is, the driver should support both, accept CMYK
   and separate dark/light cyan and magenta internally in the driver,
   or directly accept CcMmYK (6-color) from the caller.

Gutenprint does this.  It currently supports the following input
types:

* Grayscale
* Whitescale
* RGB
* CMY
* CMYK (or trivially KCMY)
* Printer-specific raw (what specific options are offered depends upon
  the printer)

I'm also thinking about RGBK.

   AFAIK, Gutenprint already has a RGB print mode, but the RGB ->
   printer color space conversion is not CM based, but rather
   heuristic.

Yup.  Actually, there are a number of choices for RGB->printer color
conversion (maximum correction, optimize for saturation, no
inter-channel correction, desaturate, threshold, density-only
correction, no correction at all, and predithered -- threshold with no
density correction).

   >For utilising most of the available gamut (within the mathematical
   >limits) n-colour separations with according linearisation seems a
   >better choice.

   Particularly if additional primaries (not just dark/light, but e.g.
   orange, green) come into the play, I see rather a strong demand to
   do the separation with a multicolor profile.

Agreed.  There's also "gloss optimizer", which is basically a clear
ink that's intended to be used in areas with little ink to even out
the ink usage and match the gloss for the entire image.

   Btw, is printing with spot colors (e.g. CMYK + two different
   Pantone inks) actually a topic which needs to be seriously
   considered? For offset printing, this is indeed a serious issue,
   but what about inkjet printing?

I think so, because of ink limiting concerns.  Dump too much ink on
the page and you might get compressed or even non-monotonic curves,
bleed-through, or even gumming up the printer.

-- 
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 Gimp Print   --    http://gimp-print.sourceforge.net

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