features - 1 Fall 2008 CAP 6938 – Topics in Pen-Based...

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Unformatted text preview: 1 Fall 2008 CAP 6938 – Topics in Pen-Based User Interfaces ©Joseph J. LaViola Jr. Features Extraction for Sketch- Based Recognition Lecture #8: Feature Extraction Joseph J. LaViola Jr. Fall 2008 Fall 2008 CAP 6938 – Topics in Pen-based User Interfaces ©Joseph J. LaViola Jr. Recall Pen-Based Interface Dataflow Raw Stroke Data Preprocessing Segmentation Feature Extraction And Analysis Classification Ink Parsing Sketch Understanding Make Inferences 2 Fall 2008 CAP 6938 – Topics in Pen-based User Interfaces ©Joseph J. LaViola Jr. Feature Extraction and Analysis ¡ What came first, the feature or the machine learning algorithm? ¡ Want to distinguish sketch components from one another ¡ Good features are critical ¡ Extract important information ¢ geometrical, statistical, contextual ¡ Examples include ¢ arc length, histograms, cusps, aspect ratio ¢ self-intersections, stroke area, etc… Fall 2008 CAP 6938 – Topics in Pen-based User Interfaces ©Joseph J. LaViola Jr. Finding Features ¡ Challenging problem ¢ need fast algorithms for gathering information ¢ features must be good discriminators ¡ Often trial and error ¡ Can be domain specific 3 Fall 2008 CAP 6938 – Topics in Pen-based User Interfaces ©Joseph J. LaViola Jr. Geometric Features (1) ¡ Number of strokes ¢ if you know how many strokes a symbol has, you can break up your recognizer into pieces (i.e., recognizer for 1 stroke symbols, recognizer for 2 stroke symbols …) ¡ Cusps ¢ smooth vs. jagged strokes ¢ distance between cusps ¡ useful for when cusps are close together/far apart Fall 2008 CAP 6938 – Topics in Pen-based User Interfaces ©Joseph J. LaViola Jr. Geometric Features (2) ¡ Aspect ratio (width / height) ¢ tall vs. flat ¡ Self Intersections ¢ loops vs. no loops ¢ strokes with write over ¢ distance between self intersections also useful ¢ use line segment intersection algorithm loops write over 4 Fall 2008 CAP 6938 – Topics in Pen-based User Interfaces ©Joseph J. LaViola Jr....
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This note was uploaded on 06/13/2011 for the course CAP 6938 taught by Professor Staff during the Spring '08 term at University of Central Florida.

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features - 1 Fall 2008 CAP 6938 – Topics in Pen-Based...

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