Computer Vision Group University of California Berkeley On Visual Recognition Jitendra Malik UC Berkeley

Computer Vision Group University of California Berkeley From Pixels to Perception Tiger Grass Water Sand outdoor wildlife Tiger tail eye legs head back shadow mouse

Computer Vision Group University of California Berkeley Object Category Recognition

Computer Vision Group University of California Berkeley Defining Categories What is a “visual category”? –Not semantic –Working hypothesis: Two instances of the same category must have “correspondence” (i.e. one can be morphed into the other) e.g. Four-legged animals –Biederman’s estimate of 30,000 basic visual categories

Computer Vision Group University of California Berkeley Facts from Biological Vision Timing Abstraction/Generalization Taxonomy and Partonomy

Computer Vision Group University of California Berkeley Detection can be very fast On a task of judging animal vs no animal, humans can make mostly correct saccades in 150 ms (Kirchner & Thorpe, 2006) –Comparable to synaptic delay in the retina, LGN, V1, V2, V4, IT pathway. –Doesn’t rule out feed back but shows feed forward only is very powerful

Computer Vision Group University of California Berkeley As Soon as You Know It Is There, You Know What It Is Grill-Spector & Kanwisher, Psychological Science, 2005

Computer Vision Group University of California Berkeley Abstraction/Generalization Configurations of oriented contours Considerable toleration for small deformations

Computer Vision Group University of California Berkeley Attneave’s Cat (1954) Line drawings convey most of the information

Computer Vision Group University of California Berkeley Taxonomy and Partonomy Taxonomy: E.g. Cats are in the order Felidae which in turn is in the class Mammalia –Recognition can be at multiple levels of categorization, or be identification at the level of specific individuals, as in faces. Partonomy: Objects have parts, they have subparts and so on. The human body contains the head, which in turn contains the eyes. These notions apply equally well to scenes and to activities. Psychologists have argued that there is a “basic-level” at which categorization is fastest (Eleanor Rosch et al). In a partonomy each level contributes useful information fro recognition.

Computer Vision Group University of California Berkeley Matching with Exemplars Use exemplars as templates Correspond features between query and exemplar Evaluate similarity score Query Image Database of Templates

Computer Vision Group University of California Berkeley Matching with Exemplars Use exemplars as templates Correspond features between query and exemplar Evaluate similarity score Query Image Database of Templates Best matching template is a helicopter

Computer Vision Group University of California Berkeley 3D objects using multiple 2D views View selection algorithm from Belongie, Malik & Puzicha (2001)

Computer Vision Group University of California Berkeley Error vs. Number of Views

Computer Vision Group University of California Berkeley Three Big Ideas Correspondence based on local shape/appearance descriptors Deformable Template Matching Machine learning for finding discriminative features

Computer Vision Group University of California Berkeley Three Big Ideas Correspondence based on local shape/appearance descriptors Deformable Template Matching Machine learning for finding discriminative features

Computer Vision Group University of California Berkeley Comparing Pointsets

Computer Vision Group University of California Berkeley Shape Context Count the number of points inside each bin, e.g.: Count = 4 Count = FCompact representation of distribution of points relative to each point (Belongie, Malik & Puzicha, 2001)

Computer Vision Group University of California Berkeley Shape Context

Computer Vision Group University of California Berkeley Geometric Blur (Local Appearance Descriptor) Geometric Blur Descriptor ~ Compute sparse channels from image Extract a patch in each channel Apply spatially varying blur and sub-sample (Idealized signal) Descriptor is robust to small affine distortions Berg & Malik '01

Computer Vision Group University of California Berkeley Three Big Ideas Correspondence based on local shape/appearance descriptors Deformable Template Matching Machine learning for finding discriminative features

Computer Vision Group University of California Berkeley Modeling shape variation in a category D’Arcy Thompson: On Growth and Form, 1917 –studied transformations between shapes of organisms

Computer Vision Group University of California Berkeley Matching Example modeltarget

Computer Vision Group University of California Berkeley Handwritten Digit Recognition MNIST : –linear: 12.0% –40 PCA+ quad: 3.3% –1000 RBF +linear: 3.6% –K-NN: 5% –K-NN (deskewed) : 2.4% –K-NN (tangent dist.) : 1.1% –SVM: 1.1% –LeNet 5: 0.95% MNIST (distortions): –LeNet 5: 0.8% –SVM: 0.8% –Boosted LeNet 4: 0.7% MNIST : –K-NN, Shape Context matching: 0.63%

Computer Vision Group University of California Berkeley

Computer Vision Group University of California Berkeley EZ-Gimpy Results 171 of 192 images correctly identified: 92 % horse smile canvas spade join here

Computer Vision Group University of California Berkeley Three Big Ideas Correspondence based on local shape/appearance descriptors Deformable Template Matching Machine learning for finding discriminative features

Computer Vision Group University of California Berkeley Discriminative learning (Frome, Singer, Malik, 2006) weights on patch features in training images distance functions from training images to any other images browsing, retrieval, classification 83/400 79/400

Computer Vision Group University of California Berkeley triplets learn from relative similarity image i image j image k want: image-to-image distances based on feature-to- image distances compare image-to-image distances

Computer Vision Group University of California Berkeley focal image version image i (focal) image j image k = x ijk d ik d ij

Computer Vision Group University of California Berkeley large-margin formulation slack variables like soft-margin SVM w constrained to be positive L2 regularization

Computer Vision Group University of California Berkeley Caltech-101 [Fei-Fei et al. 04] 102 classes, images/class

Computer Vision Group University of California Berkeley retrieval example query image retrieval results:

Computer Vision Group University of California Berkeley Caltech 101 classification results (see Manik Verma’s talks for the best yet..)

Computer Vision Group University of California Berkeley 15 training/class, 63.2%

Computer Vision Group University of California Berkeley Conclusion Correspondence based on local shape/appearance descriptors Deformable Template Matching Machine learning for finding discriminative features Integrating Perceptual Organization and Recognition