Display power management that detects user intent

A scheme has been developed that refines detection by identifying states of user presence from retrieved webcam images, such as detecting if the user is attentive or inattentive. To guard against false detections, an intermediate state, weakly attentive is included, that allows the face-detection algorithm to retrieve another webcam picture a few seconds later and recheck for a frontal face image. The scheme recognizes four states that correspond to the user's physical state. The user can also go directly from an inattentive to interactive state when he turns around to look at the display and open a file. To implement the display power management (DPM) scheme, a system is used that consists of one main coordinating function and four subfunctions: message hooking control, camera control, image processing, and power management. Once the algorithm identifies the user's state, the image-processing function sends the results to the main function, which then calls the power management function to change the power mode according to the predefined policy.