Re: [Devel] Freetype2 & gamma correction

[Owen Taylor]

On Fri, 2003-03-28 at 17:49, Matthijs Melchior wrote:
> Freetype2 & gamma correction
> 
> Where I am coming from
> ----------------------
> 
> My Linux machine runs Debian/unstable and with the installation
> of Gnome 2.2 and Mozilla 1.3, the use of freetype anti-aliassed
> fonts was increased considerably. Despite all the positive noise
> I saw, I did not like the way the text looked, it was rather
> uneven... Soo.., I have investigated this problem and found the
> reason for this effect. I like to have correct colors on my
> screen and to get the best results I have X running with
> -gamma 2.2 [Looking at the anti-aliased fonts with gamma = 1
> gives very good results indeed! (for text, colors are too dark)]

To be slightly unhelpful, let me point out that running your
display like this is completely incorrect

 A) It won't display most images you can find with fidelity
    since they have been created to be displayed with a 
    normal monitor gamma.

 B) It does not use the available levels appropriately - 
    the standard monitor gamma curve matches the response
    of the eye quite well. More levels are needed in some
    areas then other. With a linear curve, 8 bits (256 levels)
    are not nearly enough to display smooth gradients.

It actually will, on the other hand, display antialiased
text *more* accurately. I think you'll find that black-on-white 
and white-on-black text appear more similar with the
linear gamma curve than with the non-linear one.

But the black-on-white text will look worse because you
want some thickening of the text, which is what the non-linear
curve does to black-on-white text.

Regards,
                                     Owen