This tool is a work-around for displays whose brightness control is not supported by the linux kernel. It performs well on OLED displays, since these have very dark black point and their power consumption is relative to the brightness of the viewed content.
This tool can be used on an LCD display, but in that case you really want to control the brightness directly using the display backlight.
Specifically icc-brightness was developed for the Lenovo ThinkPad X1 Yoga OLED display.
Run the tool to see all options:
$ ./icc-brightness
Control OLED display brightness by applying ICC color profiles.
icc-brightness brightness max-brightness - set brightness manually
for example setting 70% brightness:
icc-brightness 70 100
icc-brightness apply - apply brightness from system setting
icc-brightness watch - continuously update to system setting
icc-brightness clean - remove all profiles generated by us
You can install to auto-start a daemon when logging-in to a Gnome session:
$ sudo make install
cp icc-brightness /usr/local/bin/
cp icc-brightness.desktop /usr/share/gnome/autostart/
The daemon will start on your next login. You can change brightness using the brightness key or any other method that controls the display "backlight".