[Openicc] [ANNOUNCE] Compicc 0.8.3

Graeme Gill graeme at argyllcms.com
Mon Nov 29 15:19:08 PST 2010

Richard Hughes wrote:
> One thing that confuses me is how you should be dealing with VCGT
> data. For profiles that have VCGT data, do you create a tonecurve for
> each channel to remove the VCGT effect before you apply the GPU
> transform or just push the VCGT data to the video card like normal?

The VCGT should be sent the the hardware - that's the idea of it.
Some hardware has higher resolution lookup table output than
the frame buffer, and therefore it is an advantage to linearise
and make neutral the hardware response with the extra resolution.
(My current graphics card has 8 bit/component frame buffer, and
  10 bit lookup table output to the D/A).

> I must admit, I'm not completely sure of the role of VCGT in a
> late-bound color workflow.

Same as always. It's hardware calibration state being carried along
by the profile. The profile assumes the hardware is in the state
described by the VCGT, so it needs to be put in that state to be valid..

Graeme Gill.

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