Re: [RFC v2 2/2] backlight: pwm_bl: compute brightness of LED linearly to human eye.

Pavel Machek
2017-12-15T20:57:44Z

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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
--
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