Hand-held devices have become widespread and provided with significant computing capabilities, which results in an increasing pressure for using these devices to perform tasks formerly limited to notebooks, like web browsing. Due to their small screens, however, hand-held devices cannot visualize directly documents that were not designed explicitly for small-screen rendering. Such documents may be rendered either at a scale too small to be useful, or at a scale that requires intensive scrolling operations by the user. Unfortunately, scrolling a small window across a large document with a hand-held device is quite cumbersome.
In this paper we propose a scrolling system much simpler and more natural to use, based on the embedded camera---a component available in every modern hand-held device. We detect device motion by analyzing the video stream generated by the camera and then we transform the motion in a scrolling of the content rendered on the screen. This way, the user experiences the device screen like a small movable window on a larger virtual view, without requiring any dedicated motion-detection hardware.
We performed an experimental evaluation aimed at assessing the effectiveness of the proposed system in the considered scenario, characterized by low image quality, unpredictable framed scene and so on. We performed an objective benchmark quantifying the accuracy of the detected trajectory and a subjective benchmark examining users' confidence with the proposed system. For the latter evaluation, we involved a panel of 20 subjects that executed a trajectory with our system and, as a comparison, with keyboard, mouse and touchpad. The results demonstrate that our approach is indeed practical.