Disclosed is a method and apparatus in which a computing device is configured to present as part of its lock-screen interface an image selected from a user's digital image library, and to receive user input designating a classification of the presented image and respond to that user input by not only recording a classification of the image but also unlocking the device. Further, each time the computing device again presents its lock-screen interface, the computing device may present a next image from the user's image library, thereby allowing the user to concurrently classify that next image as well while unlocking the device. Consequently, as a user repeatedly interacts with the lock-screen interface over time, the user may not only enjoy seeing various images from the user's image library but may also conveniently classify those images as an integral part of the user's repeated unlocking of the device.