Re: Gamma correction on G4 PowerBook
On 2003-09-30 13:28:18 +0200, Michel Dänzer wrote:
> This does indeed sound like software, as the hardware affects the
> whole screen. The X gamma correction uses the hardware though.
Do you mean the -gamma option of XFree86? I get very similar results
to xgamma with it (except that it affects the whole screen instead
of some images only).
> > In other words, here what seems to happen: Each RGB color is
> > indexed by 256 values. Instead of doing a continuous gamma
> > correction on these 256 values (as output of the graphic card), it
> > seems that the X server does a mapping 256 values -> 256 values
> > for some pixels, i.e. as if the pixel values were different.
>
> Right. The mapping is calculated using gamma curves with xgamma and
> the X server -gamma option, and they should both give the same
> result with the same values, otherwise there's a bug somewhere.
If the hardware gamma correction does a 256 values -> 256 values
mapping, then the problem is here. Why not more than 256 values
(or something analogic) for the output?
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