From: Pavel Machek <pavel@ucw.cz>
To: Enric Balletbo Serra <eballetbo@gmail.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>,
Doug Anderson <dianders@google.com>,
Enric Balletbo i Serra <enric.balletbo@collabora.com>,
Jingoo Han <jingoohan1@gmail.com>,
Richard Purdie <rpurdie@rpsys.net>,
Jacek Anaszewski <jacek.anaszewski@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
Brian Norris <briannorris@google.com>,
Guenter Roeck <groeck@google.com>,
Lee Jones <lee.jones@linaro.org>,
Alexandru Stan <amstan@google.com>,
linux-leds@vger.kernel.org,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC v2 2/2] backlight: pwm_bl: compute brightness of LED linearly to human eye.
Date: Fri, 15 Dec 2017 21:57:35 +0100 [thread overview]
Message-ID: <20171215205735.GB19442@amd> (raw)
In-Reply-To: <CAFqH_50qgvntzwvZ_n3qhpw+BA2SpYqiJgsxfCMt1piNWzgDmA@mail.gmail.com>
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Hi!
> Yes, I think that how you describe luminance and lightness is right,
> and sounds good improve the doc.
>
> To be clear the correction table for PWM values can be calculated with
> this code.
>
> OUTPUT_SIZE = 65535 # Output integer size
> INPUT_SIZE = 2047
>
> def cie1931(L):
> L = L*100.0
> if L <= 8:
> return (L/902.3)
> else:
> return ((L+16.0)/116.0)**3
>
> x = range(0,int(INPUT_SIZE+1))
> y = [int(round(cie1931(float(L)/INPUT_SIZE)*(OUTPUT_SIZE))) for L in x]
Can we just generate the table on the fly? Should not be hard to do in
fixed point, right?
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2017-12-15 20:57 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-16 14:11 [RFC v2 0/2] backlight: pwm_bl: support linear brightness to human eye Enric Balletbo i Serra
2017-11-16 14:11 ` [RFC v2 1/2] backlight: pwm_bl: linear interpolation between values of brightness-levels Enric Balletbo i Serra
2017-11-20 18:58 ` Rob Herring
2017-11-27 11:21 ` Enric Balletbo Serra
[not found] ` <CAFqH_50VqFJ-p=gRp9md4eHDHM5NpD6zPFfjwPY4LKTh2x6sHQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-11-27 23:55 ` Doug Anderson
2017-11-27 23:55 ` Doug Anderson
2017-11-27 23:52 ` Doug Anderson
2017-12-15 14:40 ` Daniel Thompson
2017-12-18 9:47 ` Enric Balletbo Serra
2017-12-18 13:15 ` Daniel Thompson
[not found] ` <20171116141151.21171-1-enric.balletbo-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>
2017-11-16 14:11 ` [RFC v2 2/2] backlight: pwm_bl: compute brightness of LED linearly to human eye Enric Balletbo i Serra
2017-11-16 14:11 ` Enric Balletbo i Serra
2017-11-30 0:44 ` Doug Anderson
[not found] ` <CAD=FV=WY-2MmjRxGGaJrQjyeWt+k4_k7j12M4LxAnnZxJF7sXw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-11-30 11:27 ` Daniel Thompson
2017-11-30 11:27 ` Daniel Thompson
[not found] ` <c6450f50-5c12-dc52-4340-b068c0b38c54-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2017-11-30 16:57 ` Doug Anderson
2017-11-30 16:57 ` Doug Anderson
2017-11-30 18:34 ` Enric Balletbo Serra
2017-11-30 18:34 ` Enric Balletbo Serra
2017-11-30 19:06 ` Doug Anderson
2017-12-15 20:57 ` Pavel Machek [this message]
2017-12-18 10:40 ` Enric Balletbo Serra
2017-12-18 10:40 ` Enric Balletbo Serra
2017-12-18 12:33 ` Pavel Machek
2017-12-18 13:53 ` Daniel Thompson
2017-12-15 14:51 ` Daniel Thompson
2017-12-18 10:27 ` Enric Balletbo Serra
[not found] ` <CAFqH_50Jqs5_5n7D019_ZxvQD1FPCZAYhaLunNm6qzj_cH3tiw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-18 13:31 ` Daniel Thompson
2017-12-18 13:31 ` Daniel Thompson
2017-12-18 16:46 ` Doug Anderson
[not found] ` <CAD=FV=VEakDGqfEkOZbuiq=FvUw46=6u9rTOgTk5FyJ9_2Rh4A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-12-18 20:21 ` Daniel Thompson
2017-12-18 20:21 ` Daniel Thompson
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