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Beyond Bags of Features: Spatial Pyramid Matching for Recognizing Natural Scene Categories. Svetlana Lazebnik, Cordelia Schmid, Jean Ponce. Presented by: Lubomir Bourdev Many of the slides by: Svetlana Lazebnik. Key Idea. Pyramid Match Kernel (Grauman & Darrell)
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Beyond Bags of Features: Spatial Pyramid Matching for Recognizing Natural Scene Categories Svetlana Lazebnik, Cordelia Schmid, Jean Ponce Presented by: Lubomir Bourdev Many of the slides by: Svetlana Lazebnik
Key Idea • Pyramid Match Kernel (Grauman & Darrell) Pyramid in feature space, ignore location • Spatial Pyramid (this work) Pyramid in image space, quantize features
Algorithm • Extract interest point descriptors (dense scan) • Construct visual word dictionary • Build spatial histograms • Create intersection kernels • Train an SVM
Algorithm • Extract interest point descriptors (dense scan) • Construct visual word dictionary • Build spatial histograms • Create intersection kernels • Train an SVM OR Weak (edge orientations) Strong (SIFT)
Algorithm • Extract interest point descriptors (dense scan) • Construct visual word dictionary • Build spatial histograms • Create intersection kernels • Train an SVM • Vector quantization • Usually K-means clustering • Vocabulary size (16 to 400)
Algorithm • Extract interest point descriptors (dense scan) • Construct visual word dictionary • Build spatial histograms • Create intersection kernels • Train an SVM
Algorithm • Extract interest point descriptors (dense scan) • Construct visual word dictionary • Build spatial histograms • Create intersection kernels • Train an SVM
Algorithm • Extract interest point descriptors (dense scan) • Construct visual word dictionary • Build spatial histograms • Create intersection kernels • Train an SVM
My experiment: Butterfly Classification Peacock Zebra
Butterflies • Dataset from Lazebnik / Schmid / Ponce 70 train / 64 test 50 train / 41 test • Images centered on the butterfly • Significant background clutter • Large pose/viewpoint variations • Scale variations: up to x4
Butterfly Results Spatial pyramid levels: 1 (No pyramid) Spatial pyramid levels: 4