Re: [Devel] Freetype2 & gamma correction

[Billy Biggs]

Artur Zaprzala (address@hidden):

> I think that physically correct is to do alpha blending in linear
> space.  For instance, notice that when you turn two light bulbs on
> instead of one you get twice as much light (energy simply sums up in
> linear space) but it is only 50% (roughly) brighter (the response of
> the eye is nonlinear).

  You're correct that the response of the eye is nonlinear, but that is
why you must do gamma correct compositing.  Light is linear, and we see
it with a non-linear response.  So, if you sum two intensities in
non-linear space, you're compensating twice.  You need to show twice the
intensity of light so that the eye can do its thing.

  See Poynton's gamma FAQ.

-- 
Billy Biggs
address@hidden