Re: program to show corrections on the video card?
Re: program to show corrections on the video card?
- Subject: Re: program to show corrections on the video card?
- From: Graeme Gill <email@hidden>
- Date: Wed, 07 Feb 2007 03:27:55 +1100
Peter Karp wrote:
One example where "Gammas" does not show the active correction of the
graphics card is the 'contrast' setting from the 'Universal Access'
options. When choosing a different ICC-profile in the Color settings
for the display some "Gammas" doesn't show the active correction in
all cases. Some profiles don't seem to be recognized by this tool.
On windows an example where the video card LUT is not reflected by the
"Display Profile" Tool is when you alter the video card LUT by the
means of the ATI driver settings.
Looking forward any ideas if such a tool exists :-)
I doubt it's possible in a reasonable manner, simply because the
information is not available at the normal software API level.
I get the impression on OS X that Apple deliberately hide the
Universal Access effects, ie. the API's that read and write the
VideoLUT's don't see it. Similarly for MSWindows, the graphic
cards drivers hide the effects of their driver settings from
the operating system VideoLUT access. Possibly the video lut
API to the graphics cards is "write only", and the API's
fake read back by caching the last value written via the API.
I would guess that you can read back LCD monitor DDC curves OK though,
but this won't tell you the full story if the video card luts are also
affecting the video stream.
You'd have to go to some heroic programming efforts to work around
this type of limitation I would guess, ie. write kernel level drivers
to access internal operating system or graphic card data structures,
and you'd probably have to reverse engineer how it all works,
and then be prepared track any changes in what you're accessing...
Graeme Gill.
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