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Sketch Recognition

Sketch Recognition. How computers understand drawings Kanjun Qiu Junior, EECS. Why do computers want to recognize drawings?. Handwriting recognition Understand diagrams Drawing > mouse/keyboard – easier & more fun!. Information in a Drawing. Each point: x, y coordinates Time Pen speed

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Sketch Recognition

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  1. Sketch Recognition How computers understand drawings Kanjun Qiu Junior, EECS

  2. Why do computers want to recognize drawings? Handwriting recognition Understand diagrams Drawing > mouse/keyboard – easier & more fun!

  3. Information in a Drawing Each point: x, y coordinates Time Pen speed Goal: Figure out what drawing is… Compare to examples!

  4. Step 1: Segment Picture Key Idea: Picture is made of symbols. How does computer figure out what a symbol is? Must segment somehow.

  5. 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.

  6. Minimum speed, Maximum curvature

  7. Step 2: Compare Pictures After segmented, can form symbols Compare each part of symbol against sample

  8. 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.

  9. 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: 0.4 0.3 0.1 0 0.2 0.8 0.1 0.8

  10. This Recognition Method Works. Occasional mistakes, but can recognize numbers/letters with 99% accuracy Extend recognition to other things…

  11. What Else Can We Do? Make fun drawable physics simulation …and other crazy stuff

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