README


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Redshift
========

Adjust color temperature of your screen according to your
surroundings. This may help your eyes hurt less if you are working in
front of the screen at night.

The program uses an X server extension adjust the color
temperature. This is done by setting appropriate gamma ramps. If you
have configured your own gamma ramps they will be overwritten but in
that case you probably care too much about color accuracy to use this
program anyway. Your graphics driver and X server needs to either
support at least RANDR version 1.3 or the VidMode extension.

The color temperature is set according to the position of the sun. A
different color temperature is set during night and daytime. During
twilight and early morning, the color temperature transitions smoothly
from night to daytime temperature to allow your eyes to slowly
adapt. At night the color temperature should be set to match the lamps in your
room. This is typically a low temperature at around 3000K-4000K
(default is 3700K). During the day, the color temperature should match
the light from outside, typically around 5500K-6500K (default is
5500K). The light has a higher temperature on an overcast day.

Currently, the program will not continously update the color
temperature but will only do so once. One way to continously update
your screen is by running:

 $ watch -n 5 -- redshift <OPTIONS..>

The command line options are explained in the following paragrphs. The
only required parameter is your current location, all other options
have reasonable defaults.

  -g R:G:B	Additional gamma correction to apply. Can also be
     		specified as -g GAMMA to set all channels to the same
     		gamma value.
  -h		Display help message.
  -l LAT:LON	Your current location in latitudes and longitudes.
  -m METHOD	Method to use to set color temperature (randr or
     		vidmode). Default is randr. In some cases one of the
     		methods will not work. In that case you may be able to
     		use the other method.
  -s SCREEN	X screen to apply adjustments to.
  -t DAY:NIGHT	Color temperature to set at daytime/night.
  -v		Verbose output.

Example (location is Copenhagen, Denmark):

 $ redshift -l 55.7:12.6 -t 6800:3500 -g 0.8 -m vidmode -v