[argyllcms] Re: CMYK Profile Problem
- From: Nikolay Pokhilchenko <nikolay_po@xxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 15 Mar 2010 10:41:08 +0300
Mon, 15 Mar 2010 10:06:36 +1100
Graeme Gill wrote:
> Because a gamut mapping from sRGB is being applied, and
> the gamut mapping attempts to map the black point of the sRGB to the
> black point of the printer.
>
> Now, one of the subtleties is that the black point of a printer
> as far as Argyll is concerned, is the darkest color with the same
> hue as black only.
Hmm... Which way the ArgyllCMS determinate the printer black point for an RGB
printer?
In my practice I can deal with different quality CMYK inks, so the "K" inks hue
may be quite high. I think it will be more robust to determine the black point
only by gamut envelope (boundaries) and to pay respect to vision adaptation to
the printer black.
May be the optimal black point will be at the intersection of the straight line
Jab 100,0,0 to 0,0,0 and gamut boundary at the gamut bottom.
Another variant is to determine the point at the straight line between Jab
0,0,0 and 100,0,0 with J=Jmin, where Jmin - the minimum achievable J value for
given gamut with given TIL (without regard for hue). The optimal black point
will be the closest for the point determined.
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