[argyllcms] Re: Colprof feature request: amount of black point hue correction control

Nikolay Pokhilchenko wrote:

I've built many profiles for "RGB" inkjet printers and struck the black point 
hue shift
problem many times. When there is no any printer RIP control (just RGB-driver 
only)
it's impossible to control printer black point (R=G=B=0). The problem is 
aggravates by
the lack of contrast on some media. Usually, the colprof is aspiring to the 
black
neutrality at the cost of maximum b/w contrast. But in some cases the higher 
contrast
(*L range) is more desirable than black neutrality or color mapping tolerance. 
May be
the feature, similar the "-k" in dispcal will be usefull for colprof too. It may
control black "fake" level for perceptual and saturation rendering intents. For
example, with "1" value the black point is about neutral, but lighter than 
darkest. The
mapping is performing as usual. With "0" value the intended black point is 
shifted to
match the darkest device combination. There will be tone shift on print, but the
contrast may be visibly higher.


Hi,

What you describe is already what is meant to happen. By default when
using gamut mapping the neutral axis mapping uses "extend and bend"
at the black point to get neutrality without compromising contrast
ratio. It seemed to be working last time I checked, but that was a
while ago.

I think you need to send me an example (.ti3, profile, options
used etc.) so that I can reproduce the problem you are seeing.

Graeme Gill.

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