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Recognition using Regions. Ghunhui Gu, Joseph J. Lim, Pablo Arbeláez, Jitendra Malik University of California at Berkeley Berkeley, CA 94720. OUTLINE. Introduction Approach Experimental Results Conclusion. Introduction. - PowerPoint PPT Presentation
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Ghunhui Gu, Joseph J. Lim, Pablo Arbeláez, Jitendra Malik
University of California at BerkeleyBerkeley, CA 94720
IntroductionApproachExperimental ResultsConclusion
Introduction
Early work in the late 90s , the domain strategy for object detection in a scene has been multi-scale scanning
: is there an instance of object category C in the window?
It differs significantly from the nature of human visual detection
So,
This paper focus on using regions , which have some properties:
(1)They encode shape and scale information of objects naturally
(2)They specify the domains on which to compute various features, without being affected by clutter from outside the region (background)
(3)But its not popular as features due to their sensitivity to segmentation error
ApproachOverview the method
Framwork for Region weighting
Main recognition algorithm(1)Voting(2)Verification(3)Segmentation
The “bag of regions” representation of a mug example
[2] P. Arbel´aez, M. Maire, C. Fowlkes, and J. Malik. From contoursto regions: An empirical evaluation. In CVPR, 2009.
All node generated by[2]
Region cues:
Contour shape, given by the histogram of oriented responses of the contour detector gPb [22]
Edge shape, where orientation is given by local image gradient (by convolution)
Color, represented by the L*, a and b histograms in the CIELAB color space
http://en.wikipedia.org/wiki/Lab_color_space
Texture, described by texton histograms
Describe a region by subdividing evenly its bounding box int an n x n grid
(a)Original image, (b) A region from the image, (c) gPb [22]Representation of the region in (b), (d) Our contour shape descriptor based on (c)
The “contour shape” region descriptor
[22] M. Maire, P. Arbel´aez, C. Fowlkes, and M. Malik. Usingcontours to detect and localize junctions in natural images.In CVPR, 2008.
Discriminative Weight Learning
I and J are objects of same category, but K is an object of a different category
Discriminative Weight Learning
The pipeline of object recognition algorithm
Voting , Verification, Segmentation three stage
Voting stage
This transformation provides not only position but also scale estimation of the object. It also allows for aspect ratio deformation of bounding boxes.
Voting
Vote of bounding box of the object(Transformation function )
Vote score
Transformation function model they use
Given a query image and an object category, is to generate hypotheses of bounding boxes and support of objects of that category in the image
Verification
The verification score
The average of the probabilities
The overall detection score --Product of the two score
Segmentation
Green for object and Red for background
To recover the complete object support from one of its parts
Experimental Results
1. ETHZ shape2. Caltech-101
Data base:
Detection performance
ETHZ shape
Region tree : on average ~ 100 regions per image
Color and texture are not very useful in this data base
Choose the functions in Eqn.11 as:
Split the entire set in to half training and half test for each category
ETHZ shapes
Caltech 101Randomly pick 5, 15 or 30 images for training and up to 15 images in disjoint set for test
Geometric blur[4]
Caltech 101
conclusionPresented a unified framework for object
detection, segmentation, and classification using regions.
(1)Cue combination significantly boosts recognition performance
(2)Reduces the number of candidate bounding box by order of magnitude over standard sliding window scheme due to robust estimation of object scales from region matching