Despite its popularity, the classic pinch-to-zoom gesture used in modern multi-touch interfaces has drawbacks: specifically, the need to support an extended range of scales and the need to keep content within the view window on the display can result in the need to clutch and pan. In two formative studies of unimanual and bimanual pinch-to-zoom, we found patterns: zooming actions follows a predictable ballistic velocity curve, and users tend to pan the point-of-interest towards the center of the screen. We apply these results to design an enhanced zooming technique called Pinch-to-Zoom-Plus (PZP) that reduces clutching and panning operations compared to standard pinch-to-zoom behaviour.
Figure 1. Illustration of transient zooming. The user wants to precisely annotate the letter T (a); she bookmarks the starting viewport using her non-dominant hand (b), zooms in, (c) annotates the T (d), and then lifts her fingers to restore the bookmarked viewport (e). Normal operations can be performed before, during or after the bookmark operation.
ABSTRACTDespite the ubiquity of touch-based input and the availability of increasingly computationally powerful touchscreen devices, there has been comparatively little work on enhancing basic canonical gestures such as swipe-to-pan and pinch-to-zoom. In this paper, we introduce transient pan and zoom, i.e. pan and zoom manipulation gestures that temporarily alter the view and can be rapidly undone. Leveraging typical touchscreen support for additional contact points, we design our transient gestures such that they co-exist with traditional pan and zoom interaction. We show that our transient pan-and-zoom reduces repetition in multi-level navigation and facilitates rapid movement between document states. We conclude with a discussion of user feedback, and directions for future research.
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