FYI,
the
input matrix->abstract->monitor
approach sugested by Marti was tested. And the former posted site updated
accordingly.
<http://www.behrmann.name/index.php?option=com_content&task=view&id=35&Itemid=73>
As Graeme pointed out, there can be done much more.
regards
Kai-Uwe Behrmann
+ development for color management
+ imaging / panoramas
+ email: [EMAIL PROTECTED]
+ http://www.behrmann.name
Am 11.05.05, 15:31 +0200 schrieb Marti:
>
> Hi,
>
> > a question about colour clipping. What I am looking for is a way
> > how to not going over Lab to avoid colour clipping. Speed is a major
> > concern.
>
>
> This relates to highlights management, which in general, is
> not very well handled by ICC workflows. A complete
> solution would need a way to encode colorant values
> above 1.0, and this is unsupported by ICC profiles.
> However, you could try some alternatives.
>
> One, which I think could do the trick, is to use abstract profiles
> for a more "smart" dynamic range limiter.
>
> An abstract profile is a specialized one going from PCS to PCS.
> Since one of the allowed PCS is XYZ, and XYZ has a way to
> encode values far above Y>1.0, you could create a XYZ->XYZ
> abstract profile holding the gamut remapping.
>
> I think Hue-preserving mindE would suffice for a first approach.
> Then, instead of using a color transform of two profiles, you could
> use a multiprofile transform and insert this abstract profile in the
> middle.
>
> i.e. instead of using:
>
> Input profile -> Render profile
>
> You could use
>
> Input profile -> abstract profile -> Render profile
>
> Then the speed penalty would be null, since the CMM would
> smelt all profiles into a single devicelink. It would take exactly
> the same time as the normal transform.
>
> Obviously this is going to work only if PCS of input profile is
> XYZ. Lab PCS is limited to L*=100, so it will be not suitable
> at all.
>
> Regards,
> --
> Marti Maria
> The littlecms project.
> www.littlecms.com
>
>
> ----- Original Message ----- From: "Kai-Uwe Behrmann" <[EMAIL PROTECTED]>
> To: "Lcms Liste" <[email protected]>
> Cc: "Robert L Krawitz" <[EMAIL PROTECTED]>
> Sent: Wednesday, May 11, 2005 1:37 PM
> Subject: [Lcms-user] Colour clipping
>
>
> > Hi,
> >
> > a question about colour clipping. What I am looking for is a way
> > how to not going over Lab to avoid colour clipping. Speed is a major
> > concern.
> >
> > One problem we run into (in CinePaint) is colour clipping during
> > displaying.
> > A oversaturated channel is not weighted against the other
> > channels, even if the information is available.
> >
> > I put a small comparision together:
> > <http://www.behrmann.name/index.php?option=com_content&task=view&id=35&Itemid=73>
> >
> > regards
> > Kai-Uwe Behrmann
> > + development for color management
> > + imaging / panoramas
> > + email: [EMAIL PROTECTED]
> > + http://www.behrmann.name
> >
> >
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