So, here's an updated version.
I still have not added the ability to use a generic brightness control in some other app.
I have fixed this to use the correct exponential curves in an LM3630A.
I've shifted the (supposedly neutral) zero point to 2/3 along.
You still have access to complete warm to complete cold with hopefully a linear range to your eye.
And I have it save your color preference when the lights are fully off (and it can't determine your color preference from the values).
Not a biggy, but if you tried running this app on your cell phone or something that didn't actually have red/blue LEDs it might have written some settings.
That's not a killer, but it will cause the later version to think that you actually do have red/blue.
Do not run these commands on a Poke.
Only run these commands on a non-Poke if you tried the first version.
Code:
$ settings delete system screen_cold_brightness
$ settings delete system screen_warm_brightness
Yes, you can run this version on your cell phone (if you want).
It should show only the Brightness slider and will work normally.
Edit: With a few more tweaks (not yet posted) it does B&N Glow3 too (although the stock pulldown is not so bad).