CALI: An Online Scribble Recognizer for Calligraphic Interfaces

Manuel J. Fonseca, César Pimentel, and Joaquim A. Jorge

CALI is a fast, simple and compact online recognizer that identifies Scribbles (multi-stroke geometric shapes) drawn with a stylus on a digitizing tablet. Our method is able to identify shapes of different sizes and rotated at arbitrary angles, drawn with dashed, continuous strokes or overlapping lines. We use temporal adjacency to allow users to input the most common shapes in drawing such as triangles, lines, rectangles, circles, diamonds and ellipses, using multiple strokes. We have further extended this approach to identify useful shapes such as arrows, crossing lines and unistroke gesture commands and have developed a library of software components to make this software generally available. The recognition algorithm uses Fuzzy Logic and geometric features, combined with an extensible set of heuristics to classify scribbles. More recently we developed a trainable version of the recognizer to allow users to easily add new shape classes to the initial core set. Evaluation results show recognition rates over 97% for the non-trainable and 95% for the trainable version.

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