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List:       gimp-print-devel
Subject:    Re: [Gimp-print-devel] Color model of data for inkjet printer
From:       Robert Krawitz <rlk () alum ! mit ! edu>
Date:       2014-08-22 0:31:09
Message-ID: 201408220031.s7M0V95l017690 () dsl092-065-009 ! bos1 ! dsl ! speakeasy ! net
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On Thu, 21 Aug 2014 20:34:42 +0000, brane2 wrote:
> Dne 21. 08. 2014 12:47, piše Robert Krawitz:
> 
> > Gutenprint converts it to the actual colorants used by the printer 
> > regardless of the input model. The colorants are actually 1 or 2 bit 
> > values corresponding to drop size (1 bit would be either print a drop 
> > or don't; 2 bits allow for 3 different drop sizes, conventionally 
> > called small, medium, and large). The more drops are printed in a 
> > given area, the darker that area looks; with small drops and high 
> > resolution, the result is smooth tones rather than dots. 
> 
> I had a few somewhat related questions that I'll try to sneak in here.
> 
> How exactly are colours mixed and how is resoution defined ?
> 
> Let's suppose I selected 720 dpi on simple 4-colour CMYK EPSON inkjet. What those \
> dpis mean exactly ? 
> Is pixel meant as simply 720x720 landing spots per each square inch and with:

Yes.

> - space for droplet of one colour, so for colour mix I have to use a bunch of \
>                 neigbouring landing spots and stipple
> - bunch of 2x2 subspace clusters, so I can mix 4 colours for each cluster
> - just as with first possibility, only with allowance for colours to actually mix, \
> so I can shoot yellow on top of cyan to get green etc.

You can print one drop of any size of each colorant at each location
in the 720x720 grid.  For example, you could print one black drop, one
gray drop, one dark cyan drop, one light cyan drop... at each spot on
the grid for a total of 8 drops at each position.

> If ink is meant to mix on paper, can I get more intense coverage by
> spitting dropplet on dropplet over same spot ?

You could in principle do this, but in practice, at any but the lowest
resolutions (720x360 and below, typically) you'll oversaturate the
paper and the result won't be more intense color at all, but rather
bleeding, puddling of ink (which makes for a real mess!), and muddy
colors.
-- 
Robert Krawitz                                     <rlk@alum.mit.edu>

MIT VI-3 1987 - Congrats MIT Engineers 6 straight men's hoops tourney
Tall Clubs International  --  http://www.tall.org/ or 1-888-IM-TALL-2
Member of the League for Programming Freedom  --  http://ProgFree.org
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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