\input texinfo   @c -*-texinfo-*-

@c %**start of header
@setfilename blueshift.info
@settitle blueshift
@afourpaper
@documentencoding UTF-8
@documentlanguage en
@finalout
@c %**end of header


@dircategory Economy
@direntry
* blueshift: (blueshift).            Automatically adjust the colour temperature
@end direntry


@copying
Copyright @copyright{} 2014 Mattias Andrée

@quotation
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
``GNU Free Documentation License''.
@end quotation
@end copying

@ifnottex
@node Top
@top blueshift -- Automatically adjust the colour temperature
@insertcopying
@end ifnottex

@titlepage
@title blueshift
@subtitle Automatically adjust the colour temperature
@author by Mattias Andrée (maandree)

@page
@vskip 0pt plus 1filll
@insertcopying
@end titlepage

@contents



@menu
* Overview::                        Brief overview of @command{blueshift}.
* Invoking::                        Invocation of @command{blueshift}.
* GNU Free Documentation License::  Copying and sharing this manual.
@end menu



@node Overview
@chapter Overview

Inspired by Redshift, Blueshift adjusts the colour
temperature of your monitor according to brightness
outside to reduce eye strain and make it easier to
fall asleep when going to bed. It can also be used
to increase the colour temperature and make the
monitor bluer, this helps you focus on your work.

Blueshift is not user friendly and it is not
meant too be. Blueshift does offer limited
use of command line options to apply settings,
but it is really meant for you to have configuration
files (written in Python 3) where all the policies
are implemented, Blueshift is only meant to provide
the mechanism for modifying the colour curves.
Blueshift neither provides any means of automatically
getting your geographical position; the intention is
that you should implement that in the policy yourself
using library which can do that. Additionally
Blueshift provides not safe guards from making your
screen unreadable or otherwise miscoloured; and
Blueshift will never, officially, add support
specifically for any proprietary operating system.
Blueshift is fully extensible so it is possible to
make extensions that make it usable under unsupported
systems, the base code is written in Python 3 without
calls to any system dependent functions.
If Blueshift does not work for you for any of these
reasons, you should take a look at Redshift.



@node Invoking
@chapter Invoking

Blueshift uses argparser to read options from the
commnad line. It inherits a few properaties from this:
abbreviations are supported, you only need to type the
beginning of the long options so that the rest can
be filled in unambiguously by the program; @option{--}
can be used, as usual, to make all following options
being parsed as just arguments; and @option{++} works
like @option{--}, except it only allied to the next
option. Any argument that is not parsed as an option
for Blueshift is passed onto the configuration script.

Blueshift recognises the following options:

@table @option
@item -c
@itemx --configurations FILE
Select configuration script. This defaults to the
first file of the following the exists:
@file{$XDG_CONFIG_HOME/blueshift/blueshiftrc},
@file{$HOME/.config/blueshift/blueshiftrc},
@file{$HOME/.blueshiftrc}, @file{/etc/blueshiftrc}.
Blueshift does not check the user home, rather it
checks @env{HOME} which should be the user home, unless
you change it yourself.

@item -p @c the long name of option is inspired from openntpd
@itemx --panic-gate
@itemx --panicgate
Applies the settings directly instead of transitioning
into the initial settings. There is not option for doing
this when the program exists. But you press @kbd{Control+c}
twice, or send SIGTERM twice, to skip transition into
default settings.

@item -h
@itemx -?
@itemx --help
Prints help information.

@item -C
@itemx --copying
@itemx --copyright
Prints copyright information.

@item -W
@itemx --warranty
Prints non-warranty information,
included in the copyright information.

@item -v
@itemx --version
Prints the name of the program and the
installed version of the program
@end table

Blueshift also supports a few options
for ad-hoc settings. These are ignored
(unlessed fetched by the configuration file)
if @option{-c} (@option{--configurations})
is used.

@table @option
@item -g
@itemx --gamma RGB
Apply gamma correction to the colour curves.
All values in the three colour curves are raised
to the power of 1 divided by @var{RGB}. Assuming
no values in the curves are larger than 1 (100 %)
the curves are bent upwards if @var{RGB} is larger
than 1.

@item -g
@itemx --gamma R:G:B
This works as @option{--gamma RGB}, except the
gamma is applied separately for the three colour
curves. If we want to apply the 0,9 gamma to the
red colour component, and 1,1 and 1,2 for the
green and blue colour components, respectively use
@option{-g 0.9:1.1:1.2} or @option{-gamma 0.9:1.1:1.2}.

@item -b
@itemx --brightness RGB
This multiplies all values in the colour curves
with @env{RGB}, effectively making the display
@env{RGB} times as bright. Values larger than 1,
will be clipped to 1. This is indented to be used
to make the screen slightly darker during the night.

@item -b
@itemx --brightness R:G:B
This option is to @option{--brightness RGB} as
@option{--gamma R:G:B} is to @option{--gamma RGB}.

@item +b
@itemx ++brightness Y
This option works as @option{--brightness RGB},
except the CIE xyY colour spaces is used instead
of sRGB and will probably make the colour curves
look better.

@item -t
@itemx --temperature TEMP
Changes the colour tempurature to @var{TEMP}
kelvin. The standard colour tempurature is
6500 K@footnote{Or actually 6504 K using revised
constants in Plank's law}. If not specified,
the colour temperature will be 3700 K during
high night and 6500 K during the high day.

@item -l
@itemx --location LAT:LON
Specify your geographical coordinates. This
is used to determine how dark it is outside.
@env{LAT} is the latitude, floating point
measured in degrees from the equator to the
north. It is negative if you are on the
southern hemisphere. @env{LON} is the
longitude, floating point measured in degrees
from Greenwich to the east. Negative if you
are on the west side of the Earth.

@item -r
@itemx --reset
Transition from the specified settings to
normal, clean, settings.

@item -o
@itemx --output
@itemx --crtc CRTC
Select CRTC to apply changes to. This is
comma separated list, and multiple options
may be used. It is best to start one
instance per monitor with colour calibration.
@end table

@option{-g}, @option{-b}, @option{+b}, and
@option{-t} can be use twice, each, to use
different settings during the night and during
the day. While this is possible for gamma,
it is not recommended. The purpose of gamma
is to adjust the same error that are present
in minors and make all colours look correct
in relation to each other.



@node GNU Free Documentation License
@appendix GNU Free Documentation License
@include fdl.texinfo

@bye