Is there any way to change screen brightness to 50% or 25%? I don't mean real backlight brightness control. I need to limit RGB signal level from <0,255> to <0,127> or <0,63>, preferred separate control for each color channel. I tried xrandr but it doesn't support brightness control on rPi
Why I asking for that? Because my custom build use ESP8089 (ESP-12) in SDIO mode as wifi card and DIY VGA666 as video output. That eats almost all GPIO lines. I can limit color range to 4b per color by removing resistors from LSB color lines. Then I can switch lines into different ALT mode to use them as GPIO lines. Sadly this way I can't access few useful peripherals because VGA666 overlay pins can't be remapped.
IMO if I dim video output to <0,63> range I can reuse two MSB instead of two LSB. This should allow me to reuse different GPIO pins and access peripherals I need.