This is a Python2 application that sets the screen backlight (brightness) according to the ambient light. It uses a camera (usually a web-cam) to detect the level of luminosity in the ambient and calculates and sets the appropriate backlight value.
Following the Python way of coding, the app code is mostly self explanatory and well documented. To adjust it's behavior to fit your preferences, you must modify some constants in the beginning of the code.
Is the directory that holds the files brightness and max_brightness. The file brightness is the one that actually controls the backlight level. It is usually /sys/class/backlight/something.
This variable is optional if the command 'xbacklight' (by Xorg) works in your computer.
Constants that adjust the relation between the ambient light level and the backlight level Should be modified until you get comfortable with the backlight changes.
You can think about these constants like the angular coefficient (slope) and the linear coeficient of a straight line equation
BackLight = AmbLight*GAIN + BASE_LINE (the AmbLight will be in a 0 to 1 scale).
The number of images captured and adjustments per minute that this app is gonna do. I recommend 60 (1 adjustment per second).
Set the maximum number of steps from the minimum to the maximum value of brightness. It's useful to avoid constantly little changes. I think 10 is a good number for that.
First, you must have the Python library opencv. In ArchLinux, just install this package: sudo pacman -S opencv. In Ubuntu, you can type sudo apt-get install python-opencv.
Now, you can download the zip containing the files and extract it to someplace in you computer.
If you have the xbacklight command working in your computer, great! To test, just type xbacklight -set 0. The backlight should go down to it's minimum value. Typing xbacklight -set 100, should set the maximum value. If the xbacklight doesn't work, you have to specify the SYS_PATH variable in the autobacklight.py and also run it with sudo.
With that said, open a terminal and go to the place you extracted the files. You can type python2 autobacklight.py or sudo python2 autobacklight.py (if you had set a SYS_PATH). The app should be running by now.
You will see two lines being constantly printed, containing the ambient light level read from the camera and the correspondent backlight that is been set. To stop it, press ctrl+c. Now is the time to modify the other variables in the file autobacklight.py and test the results.
Once you have set the variables for your preferences and the app is working fine, you can do the following in order to auto start it on login:
cp autobacklight.desktop ~/.config/autostart
sudo mkdir /opt/autobacklight
sudo cp autobacklight.py /opt/autobacklight/autobacklight.py
Now, it should start in background on the next login. This works fine if you are using xbacklight.
If you are not (and had set the SYS_PATH), theres no a good way to make it start at login. One solution is to change the Exec line of autobacklight.desktop to sudo /opt/autobacklight/autobacklight.py &, then make the file executable with sudo chmod +x /opt/autobacklight/autobacklight.py and finaly add the line USERNAME ALL = NOPASSWD: /opt/autobacklight/autobacklight.py to the /etc/sudoers file (use sudo visudo for that). Replace USERNAME by you user name.
It works, but I do not recommend messing up with your /etc/sudoers file unless you know what you're doing.
Sooner I'm gonna create the systemd service files, which will resolve this issue.