noto_miller - User-Directed Sketch Interpretation Matthew J...

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User-Directed Sketch Interpretation Matthew J. Notowidigdo Robert C. Miller MIT Computer Science and Aritifical Intelligence Laboratory 10 Vasser St Cambridge, MA 02139 [email protected] ABSTRACT This paper presents a novel approach to creating structured diagrams (such as flow charts and object diagrams) by com- bining an off-line sketch recognition system with the user interface of a traditional structured graphics editor. Our sys- tem, called UDSI (user-directed sketch interpretation), aims to provide drawing freedom by allowing the user to sketch entirely off-line using a pure pen-and-paper interface. The results of the drawing can then be presented to UDSI, which recognizes shapes and lines and text areas that the user can then polish as desired. The system can infer multiple inter- pretations for a given sketch, to aid during the user’s pol- ishing stage. The UDSI program offers three novel features. First, it implements a greedy algorithm for determing alterna- tive interpretations of the user’s original pen drawing. Sec- ond, it introduces a user interface for selecting from these multiple candidate interpretations. Third, it implements a cir- cle recognizer using a novel circle-detection algorithm and combines it with other hand-coded recognizers to provide a robust sketch recognition system. KEYWORDS: sketch recogntion, user interfaces, HCI, ma- chine vision INTRODUCTION Structured diagrams (e.g. flow charts, module dependency diagrams) are commonly created using an editor such as Vi- sio or XFig. These applications are powerful and expressive, but they are cumbersome to use, and they make it difficult to communicate drawing styles and shape sizes. Realizing the shortcomings of the user interfaces of these applications, re- cent research has focused on sketch understanding systems that recogize hand-drawn structured diagrams [2, 7]. These systems use stroke information collected on a tablet com- puter to recognize parts of the diagram as the user sketches them. While these systems are more natural to use than the menu- and mouse-driven editors, they have subtle deviations from an actual pen-and-paper interface. For example, adding an arrowhead to a line segment that was drawn much ear- lier may confuse the system since the recognition depends on temporal information. The user must delete the line seg- ment and redraw it with the arrowhead. Figure 1: Original pencil sketch (scanned) Figure 2: User editing a recognized sketch in UDSI UDSI (User-Directed Sketch Interpretation) is a new system for creating structured diagrams that is based on understand- ing hand-drawn sketches of structured diagrams. Unlike ex- isting systems that require devices that can capture stroke in- formation while the user sketches the diagram, UDSI uses scanned images of sketches. The user presents a scanned pen sketch of the diagram to UDSI and guides the application’s interpretation of the sketch. The final result is a structured di- agram that can be incorporated into technical documents or
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noto_miller - User-Directed Sketch Interpretation Matthew J...

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