Hi,
On 1/31/22 08:10, Alexander Dahl wrote:
I know that color curves were being discussed at the time multicolor
was being introduced, and AFAIK Pavel didn't like it, but I don't
remember the reasons anymore.
As far as I understand it though, for PWM LEDs there is an equation for
gamma correction.
That's right, and it gets a little more complicated if you have RGB
instead of a single LED. A start for reading might be this:
https://hackaday.com/2016/08/23/rgb-leds-how-to-master-gamma-and-hue-for-perfect-brightness/
(I had bookmarked that back when I was hacking on firmware for an 8bit
microcontroller controlling an RGB LED through soft PWM few years
ago. A very simple solution is a precalculated static lookup table.)
This is a very interesting topic which I was gonna ask about on this
list anyways. IMHO, the Linux leds subsystem needs a uniform way to deal
with lightness/gamma correction. There is some previous work in pwm_bl
and led_bl with their `brightness-levels` device tree property and
cie1931 correction function (drivers/video/backlight/pwm_bl.c). It would
be very nice to have this functionality in the led class. Having
something similar for multi-color as well would be fantastic.
Sven
