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Re: [ft-devel] gamma correction demo images

From: Alexei Podtelezhnikov
Subject: Re: [ft-devel] gamma correction demo images
Date: Wed, 4 Nov 2015 10:27:15 -0500

On Wed, Nov 4, 2015 at 6:24 AM, Nikolaus Waxweiler <address@hidden> wrote:
> Any progress, Alexei? :)

I am sitting here in total disbelief and utterly embarrassed by the
lack of gamma correction setting for text rendering in any major Linux
desktop environment. How could this happen? Pango and Qt do not do it
either. I think FreeType is to blame for the lack of support, because
everybody just trusts FreeType. We need new FT_RENDER_MODE_GAMMA.

I am also confused. It seems obvious how to do it for grayscale
rendering . But what about subpixel rendering? I mostly see
application of gamma correction per each RGB channel, which seems
totally arbitrary. See attached image for wonderful color effects on
slightly slanted lines of 1, 4/3, 5/3-pixel wide and so on. I also
found a reference of HSL lightness gamma correction, which seems more
justifiable to me. I have not tried it yet. How does alpha blending
works on subpixel level, or does it at all? Then there is LCD
filtering to deal with color fringes, which changes RGB values and
begs the question if gamma correction is even suitable after this
brutal treatment. Perhaps you can enlighten me here.

It seems to me that gamma was considered a good idea, but subpixel
rendering got in the way, and now we are all stuck.


Attachment: GammaMoireRGB.png
Description: PNG image

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