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Published byHomer Burns Modified over 8 years ago
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Sketch Recognition How computers understand drawings Kanjun Qiu Junior, EECS
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Why do computers want to recognize drawings? Handwriting recognition Understand diagrams Drawing > mouse/keyboard – easier & more fun!
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Information in a Drawing Each point: x, y coordinates Time Pen speed Goal: Figure out what drawing is… Compare to examples!
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Step 1: Segment Picture Key Idea: Picture is made of symbols. How does computer figure out what a symbol is? Must segment somehow.
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Finding Corners When drawing corners, pen slows down Minimum speed Maximum curvature (sharp turn) Goal: Find spots with minimum speed & maximum curvature, call them corners.
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Minimum speed, Maximum curvature
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Step 2: Compare Pictures After segmented, can form symbols Compare each part of symbol against sample
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Extension: Stroke Direction Find direction at each point in stroke Divide into 4 images – 0, 45, 90, 135 degree strokes If point within 45 degrees, draw with some intensity Compare 4 images instead of 1 Using 4 images = greater accuracy.
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How to Compare? Distance. Find distance ( just subtract ) between intensities of samples at each point Smallest distance = closest match How to calculate distance for a 2x2 picture: 0.3 0 0.10.8 0.4 0.1 0.20.8
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This Recognition Method Works. Occasional mistakes, but can recognize numbers/letters with 99% accuracy Extend recognition to other things…
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What Else Can We Do? Make fun drawable physics simulation …and other crazy stuff
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