Webcam Tools

Clight – webcam becomes light sensor

Clight is software that turns your webcam into a light sensor. The software adjusts the screen backlight based on the ambient brightness in your surrounding from captured webcam frames.

The software also manages the screen temperature, and dims the screen after a timeout. Its dimmer module functions without a webcam.

The software is released under an open source license. It’s written in the C programming language.

Features include:

  • Very lightweight.
  • Support for external monitors.
  • Fully valgrind and cppcheck clean.
  • External signals catching (sigint/sigterm).
  • systemd user unit shipped.
  • Quick single capture mode (i.e. do captures, change screen brightness and leave) is provided through a desktop file.
  • GAMMA support – computes sunset and sunrise and will automatically change screen temperature.
  • DIMMER support – dims your screen after specified timeout of user inactivity (i.e.. no mouse/keyboard activity).
  • DPMS support – set desired dpms timeouts for AC/battery states.
  • Both DPMS and DIMMER can be disabled while on AC.
  • geoclue2 support: when launched without [–lat|–lon] parameters, if geoclue2 is available, it will use it to get user location updates. Otherwise gamma support will be disabled. Location received will be then cached when clight exits. This way, if no internet connection is present (geoclue2 cannot then provide the location) at restart, clight will load the latest available location from a cache file. If no cached location is present, gamma is disabled.
  • –sunrise/–sunset times user-specified support: gamma nightly temperature will be set at sunset time, daily temperature at sunrise time.
  • Log file, placed in $HOME/.clight.log.
  • More frequent captures inside “events”: an event starts by default 30 minutes before sunrise/sunset and ends 30mins after. This is configurable.
  • conf file placed in both /etc/default and $XDG_CONFIG_HOME (fallbacks to $HOME/.config/) support.
  • Lots of configurations available.
  • Only 1 clight instance runs for each user.
  • Sweet inter-modules dependencies management system with “modules”(BRIGHTNESS, GAMMA, LOCATION, etc.) lazy loading: every module will only be started at the right time, e.g. GAMMA module will only be started after a location has been retrieved. And modules are gracefully auto-disabled where unsupported (e.g. GAMMA on non-X environments).
  • UPower support, to set longer timeouts between captures while on battery, in order to conserve energy.
  • Specify curve points to be used to match ambient brightness to screen backlight from config file.
  • Clight supports org.freedesktop.PowerManagement.Inhibit interface. This offers the ability, for example, to ensure dimmer doesn’t dim your screen when watching a video.
  • Supports both internal laptop monitor and external monitors, courtesy of ddcutil.
  • Auto-disable brightness module on PCs without a webcam.
  • Check clightd version on clight startup.
  • Smooth gamma/dimmer/backlight transitions.
  • clight bus interface (org.clight.clight) to make it easy to create a GUI/applet.

Support: Wiki
Developer: Federico Di Pierro
License: GNU General Public License v3.0

Clight is written in C. Learn C with our recommended free books and free tutorials.

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