[Gimp-print-devel] 6-color generation

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

I'm trying to work out how to generate 6-color (e. g. CMYKRB) from
RGB, CMY, or CMYK input.

My thought is that the first thing we should do is generate CMYK, and
then treat the K as an independent channel.  So the problem now
becomes how to convert CMY to CMYRB or whatever the additional
channels are.

There's some very ad hoc code in there right now.  It basically does
the same kind of thing as black generation, where it looks at the
amount of min(c,m) and min(m,y) to figure out the virtual blue and red
components, and it generates the appropriate amount of the larger one
of these.

My experiments suggest that it wouldn't actually work too well.  In
particular, the blue ink isn't anything close to half way between cyan
and magenta; it's more of a bright purple.  The red is also much
closer to magenta than to yellow.

It would seem to me that a matrix would be a better way of handling
this; a 3x5 matrix can generate 5 output colors from 3 inputs.  I'm
just having a hard time visualizing what the coefficients would look
like.

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

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

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