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CV in a Nutshell (I)
Yi Lihttp://users.cecs.anu.edu.au/~yili/
CVinNutshell.htm
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Outline
• Introduction• Image Formation• Early vision• Cognition in psychology• Face recognition (I)
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Paper discussion (1)
• Recognition by Components:– Segmentation: blocks, cylinders, wedges, cones– Curvature, collinearity, symmetry, parallel– Contour, surface, texture– Occlusion– Top-down or bottom-up?– Relation: pairwise?
http://euron.upc.es/dbtm/show_image.php?id=36
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Paper discussion (2)
• Face Recognition– extremely low-resolution images (Yang and Ma)– Occlusion (sparse)– Component vs hollistic– Context! – Facial expression (Cohn)– Illumination (Basri and Jacobs)– Specialized (Martinez)
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Image Formation
• Geometry– image plane– projection
• Physics of light– Brightness / Illumination– Light source– Lambertian
• scattered such that the apparent brightness of the surface to an observer is the same regardless of the observer's angle of view (wiki)
nikonweb.com
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Lighting
http://www.cs.umd.edu/~djacobs/CMSC828/Lighting.pdf
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Early Vision
• Early year of computer vision– David Marr (Psychologist, MIT)– Azriel Rosenfeld (Mathematician, Maryland)– Takeo Kanade (Engineer, CMU)
• Visual path– How early?– Recognition?– Saliency / gist
scienceblogs.com
http://i.neoseeker.com/mgv/436139-Triforce%20of%20Wisdom/139/15/lizard_display.jpg
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Illusion
• Aperture problem• http://www.cfar.umd.edu/~fer/optical/move
ment2.html• http://www.michaelbach.de/ot/
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Skeletonization
http://www.inf.u-szeged.hu/~palagyi/skel/skel.html
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Template Matching
• Find transformation to align two images• cost function• Example: Chamfer Matching
• Example 2: Hough transform• Example 3: Probabilistic voting
http://www.gavrila.net/Research/Chamfer_System/chamfer_system.html
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Deformable
• Shape matching– Shape Context
• Snake– Active Contour, Active Appearance
• Articulated objects– Scissor– Human body
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Face Recognition
• Linear subspaces– PCA and LDA– Eigenfaces vs Fisherfaces
http://www.cs.umd.edu/~djacobs/CMSC828/LinearSubspacesGeometry.pdf
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Q/A
• Introduction• Image Formation• Early vision• Cognition in psychology• Face recognition (I)