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A SAMPLE RECOGNITION PROBLEM Joseph Tighe University of North Carolina at Chapel Hill
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What is recognition?
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He et al. (2004), Hoiem et al. (2005), Shotton et al. (2006, 2008, 2009), Verbeek and Triggs (2007), Rabinovich et al. (2007), Galleguillos et al. (2008), Gould et al. (2009), etc. Figure from Shotton et al. (2009)
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What is recognition? Have some entity photo bounding box in photo pixel Assign semantic meaning scene type, tags, sentence object label, action semantic class, material, geometric orientation
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Our Problem Entity: Images Goal: Assign 1 of 4 labels (airplane, car, face, motorbike
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Finding Similar Images
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Ocean Open Field Highway Street Forest Mountain Inner City Tall Building What is depicted in this image? Which image is most similar? Then assign the label from the most similar image
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Pixels are a bad measure of similarity Most similar according to pixel distanceMost similar according to “Bag of Words”
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Origin of the Bag of Words model Orderless document representation: frequencies of words from a dictionary Salton & McGill (1983) US Presidential Speeches Tag Cloud http://chir.ag/phernalia/preztags/
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What are words for an image?
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Wing Tail WheelBuildingPropeller
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Wing Tail WheelBuilding PropellerJet Engine
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Wing Tail WheelBuilding PropellerJet Engine
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Wing Tail WheelBuilding PropellerJet Engine
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But where do the words come from?
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Then where does the dictionary come from?
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Example Dictionary Source: B. Leibe
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Another dictionary … … … … Source: B. Leibe
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Fei-Fei et al. 2005
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Outline of the Bag of Words method Divide the image into patches Assign a “word” for each patch Count the number of occurrences of each “word” in the image
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Matlab Demo
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