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Front-end computations in human vision . Jitendra Malik U.C. Berkeley References: DeValois & DeValois,Hubel, Palmer, Spillman &Werner, Wandell. Cerebral Cortex. Monocular Visual Field: 160 deg (w) X 135 deg (h) Binocular Visual Field: 200 deg (w) X 135 deg (h). Cones and Rods.
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Front-end computations in human vision Jitendra Malik U.C. Berkeley References: DeValois & DeValois,Hubel, Palmer, Spillman &Werner, Wandell
Monocular Visual Field: 160 deg (w) X 135 deg (h)Binocular Visual Field: 200 deg (w) X 135 deg (h)
Modeling simple cells • Elongated directional Gaussian derivatives • 2nd derivative and Hilbert transform • L1 normalized for scale invariance • 6 orientations, 3 scales • Zero mean
Orientation Energy • Gaussian 2nd derivative and its Hilbert pair • Can detect combination of bar and edge features; also insensitive to linear shading [Perona&Malik 90] • Multiple scales
Textons (Malik et al, IJCV 2001) • K-means on vectors of filter responses
Texton Histograms Chi square test: i 0.1 j k 0.8