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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