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Re: [ft-devel] gamma correction demo images

From: Werner LEMBERG
Subject: Re: [ft-devel] gamma correction demo images
Date: Mon, 23 Nov 2015 09:08:07 +0100 (CET)

>> I did some experimentation with my crazy patterns.  I firmly
>> believe now that simple box filter aka FT_LCD_FILTER_LIGHT is not
>> just good but in fact the best in reducing color fringes IFF used
>> with correct gamma.  All color-balanced filters with gamma
>> eliminate color fringes completely, but the box filter is obviously
>> the least blurry of them all.  So I reached the same conclusion as
>> this paper:
> Interesting paper, although I know too little about the science
> behind it to comment on how valid these results are on a wide range
> of screens.  The paper itself states that numbers may vary
> significantly between displays and viewing conditions.
> Here's a comparison of the paper's filter to FT's light filter:
> (no stem darkening).  The
> paper's filter appears slightly sharper or more contrasty on my
> monitor but also slightly more colorful than FT's light filter.
> Werner, Dave, what's your opinion on this?  I would like to change
> the documentation of ftlcdfil.h to note that stem darkening is
> better than filters going over 0x100 and update the filter
> recommendation to the light filter for now.  Also, where does the
> [a-c, a+c, 2a, a+c, a-c] formula come from?  Is the "[a b c b a]
> where 2a+2b+c=1" formula newer?  I could include the paper's filter
> in the documentation and sprinkle it with some source citations.
> [1]: [a, b, c, b, a] where a = 0.0, b = 0.3, c = 1 - 2a - 2b = [0,
> 0.3, 0.4, 0.3, 0] =~ [0x00, 0x4D, 0x66, 0x4D, 0x00] with slight
> rounding errors ;)

David, please help answering this – my knowledge is too limited
here :-)


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