Hi,

I have a question with regards to gamma correction support in XFree86 that 
maybe someone in this mailing list can answer me.

My problem comes when I change the gamma ramps using 
XF86VidModeSetGammaRamp(). If after that I query about the gamma correction 
value using XF86VidModeGetGamma() I get the last value set with 
XF86VidModeSetGamma(). The new ramp can have totally diferent gamma value if, 
for example, I change the ramp to adjust not only this value but brightness 
and contrast too. Or the gamma correction value can makes no sense for a 
special ramp loaded in the LUT.

What is the right way to handle this situation? I'm coding a control panel 
application for XFree86 to modify gamma value, brightness and contrast, but 
as I can't really trust in the value from XF86VidModeGetGamma() I have to 
reset the ramp to a know state before launch the panel. And if I use 
XF86VidModeGetGammaRamp() I get the entries from the LUT, but I can't recover 
a gamma correction value since, as I point previously, the ramp maybe holds a 
curve for which a gamma correction value makes no sense.

AFAIK, in SGI's IRIX OS the workaround is a file, system.glGamma, that holds 
the current value of gamma correction, as set with the gamma utility 
(something like the xgamma in XFree86). This works if you only set the gamma 
correction value, but the problem comes here too if you modify the ramps to 
something diferent to the typical 'gamma curve'.


Thanks in advance

Davor

--
Davor Buvinic
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