Yawls stands for Yet Another Webcam Light Sensor, it is a small Java program created for Ubuntu, it adjust the brightness level of your display by using the internal/externel webcam of your notebook as an ambient light sensor, that uses the OpenCV Library and designed to comfort and save energy of your laptop battery.
Yawls can also be used from command line interface and run itself as a system daemon, two times a minute it runs and adjusts the brightness of the notebook screen with reference to the ambient brightness.