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Re: [ft-devel] gamma correction demo images

From: Nikolaus Waxweiler
Subject: Re: [ft-devel] gamma correction demo images
Date: Sun, 22 Nov 2015 13:21:55 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0

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 ;)

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