Re: ICC applying in macOS 10.12
Re: ICC applying in macOS 10.12
- Subject: Re: ICC applying in macOS 10.12
- From: Florian Höch <email@hidden>
- Date: Wed, 26 Jul 2017 18:50:34 +0200
Am 26.07.2017 um 15:18 schrieb Vitaly Bondar:
> Lets assume i want to have calibration to sRGB and to have accurate
> display profile.
>
> I do next steps:
> 1. apply "generic rgb profile" to display
> 2. make calibration to sRGB
> 3. apply copy of generic profile + vcgt
> 4. measure everything and calculate icc v4 profile
> 5. apply icc v4 profile + vcgt
>
> After point 3 i have calibrated display, but not accurate profile.
Is your goal to implement a calibration/profiling solution?
I guess what you're trying to achieve in steps 1 through 3 is a 'null'
transform, but technically you can just tag the pixel buffer of your
test patch window with the current display profile color space
(CGColorSpace derived from ColorSyncProfileRef) and then set the gamma
table using CGSetDisplayTransferByTable (as long as you remember that
this is transient while the calling process is alive, not persistent),
without first changing the actual display profile.
> After point 5 my display is not sRGB anymore. It is gamma 1.8, the same
as in Generic RGB profile.
Well, no. If you look at the tone response graph of the generated
profile, you should see it follows the sRGB curve (at least it should if
a null transform was used and the calibration was set during the
characterization measurements).
> This happens because XYZ->RGB transformation from my profile is now used
> before graphics-board will apply LUTs from vcgt.
And this is how it needs to be for the profile to produce the intended
result, because the correct RGB numbers that need to be sent to the
display to produce the intended intensity (or color) will only be
arrived at after going through the videoLUT.
Florian.
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