Lecture-17-h - Lecture-17 Computing Optical Flow: Lucas...

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1 Lecture-17 Kanade Global Flow • Optical flow eq t y x f v f u f - = + 9 9 9 1 1 1 t y x t y x f v f u f f v f u f - = + - = + M - - = 9 1 9 1 9 1 t t y y x x f f v u f f f f M M M t f Au = Consider 3 by 3 window
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2 t T T t T T t f A A A u f A Au A f Au 1 ) ( - = = = 2 ) ( min t yi xi f v f u f + + Lucas & Kanade 0 ) ( 0 ) ( = + + = + + yi ti yi xi xi ti yi xi f f v f u f f f v f u f 2 ) ( min t yi xi f v f u f + +
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3 ( f xi u + f yi v + f ti ) f xi = 0 ( f xi u + f yi v + f ti ) f yi = 0 f xi 2 u + f xi f yi v = - f xi f ti f xi f yi u + f yi 2 v = - f yi f ti f xi 2 f xi f yi f xi f yi f yi 2 u v = - f xi f ti - f yi f ti Lucas & Kanade - - = - ti yi ti xi yi yi xi yi xi xi f f f f f f f f f f v u 1 2 2 - - - - - = ti yi ti xi xi yi xi yi xi yi yi xi yi xi f f f f f f f f f f f f f f v u 2 2 2 2 2 ) ( 1 - - = - + - = 2 2 2 2 2 2 2 2 ) ( ) ( yi xi yi xi ti yi xi yi xi ti xi yi xi yi xi ti yi yi xi ti xi yi f f f f f f f f f f f v f f f f f f f f f f f u
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4 Comments • Horn-Schunck and Lucas-Kanade optical method works only for small motion. • If object moves faster, the brightness changes rapidly, 2x2 or 3x3 masks fail to estimate spatiotemporal derivatives. • Pyramids can be used to compute large optical flow vectors. Lucas Kanade with Pyramids • Compute ‘simple’ LK at highest level • At level i • Take flow u i- 1 , v i- 1 from level i- 1 • bilinear interpolate it to create u i * , v i *
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This note was uploaded on 06/12/2011 for the course CAP 5415 taught by Professor Staff during the Fall '08 term at University of Central Florida.

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Lecture-17-h - Lecture-17 Computing Optical Flow: Lucas...

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