Hello Gerhard,
Thank you for the quick reply. I get your thougt for the first step
when you create the device link, this one is not usable for icc2ps
-right?
Then you use icclink from lcms which does n o t create a device link,
instead it creates a kind of smelted profile out of the formerly
created device link and again the RGB input profile. So the conversion
chain amounts to RGB > RGB > CMYK, where RGB > RGB ideally
should not change the result. Did I get your idea right or is there a
mistake in my thoughts?
Greetings from Vienna
Thomas
Gerhard Fürnkranz schrieb:
-------- Original-Nachricht --------
Datum: Mon, 17 Dec 2007 09:30:22 +0100
Von: Thomas Lunzer <[EMAIL PROTECTED]>
But is there a way to bypass this for black text
and line art? I looked through the code of the firmware
of our printer, but could not find anything regarding
this behaviour. I suspect the lookup tables of the
original crd’s were edited by hand to print black rgb
text as pure 100%K. I am not really familiar with the
internals of colour transformations, so does any one
have a hint for me where to start out?
For http://sourceforge.net/projects/m2300w I had to solve the same problem. I wanted to offer an "auto" print mode, which eventually prints pure text pages with black toner only (which is also much faster on these revolver laser printers).
The "icclink" utility of Argyll CMS offers an option -f to render neutral colors with black ink only. So for achieving the goal I selected an intermediate RGB colorspace (I did choose sRGB) and created a device link from this RGB color space to the printer's CMYK space with Argyll's "icclink -f...". Then I recombinded the RGB profile with the device link with the LCMS utility icclink in order to obtain an output profile which can be fed into icc2ps.
This is surely not optimal, as the overall gamut is also bounded to the gamut or the intermediate RGB color space, and because the device link is resampled again, which indeed won't improve the acuracy, but it seems to be sufficient for consumer applications, where people typically print sRGB data anyway.
(It is possible that I also had to tweak the resulting CRD a little bit manually to workaround numerical inaccuracies - I don't remember).
Regards,
Gerhard
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