A Codebook-Free and Annotation-free Approach for Fine-Grained Image Categorization Authors Bangpeng Yao et al. Presenter Hyung-seok Lee ( 이형석 ) CVPR 2012
What is Fine-Grained Categorization? Task of classifying object that belong to the same basic-level category Bird species Flowers Stonefly larvae 2 Red Eyed Vireo Red Headed Woodpecker
Related Work (1) Codebook-based approach Encoding local image patches to visual codewords Large loss of finer details important for Fine-grained 3
Related Work(2) Annotation-based approach Human annotation of object attributes or keypoint Labor cost high and Non-automatic 4 Ref : Multiclass Recognition and Part Localization with Humans in the Loop, Catherine Wah et al.
Overview 5 Template Matching Feature response map Novel bagging-based algorithm 1. Feature Extraction 2. Feature Representation 3. Classification
Template Matching Generate a large number of templates by randomly sampling rectangular regions from all training images 6
Input image is represented by the response score of matching it self with each of the template It can captures the subtle distinctions 7
Feature representation 8 1 step : Three-largest response score 2 step : Largest score on each region
9 Final image representation is formed by concatenating the pooling results of all the templates on all image scales No. templates x No. scales X 7 dimensional
Bagging Based Classification 10 Motivation Large # of template high dimensional feature It provide richer image representation & capture more subtle visual distinction
11 But over-complete & non-discriminative element Conventional classification such as single SVM suffer from overfitting
12 Traditional bagging method Randomly select element from image feature vector Aggregating set of classifiers Ref : Model averaging Avoid overfitting
13 Novel bagging-based algorithm Full usage of available template matching results
14 Guarantees that the correlation between the classifiers are small C : Regularization T : Correlation tolerance
Experiments CUB-2010 (200 bird species, bounding box) 14 birds species from the vireos and woodpeckers families Experiment setup Randomly generate 100 template per training image Scaling factor : x 100 x 3 x 7 = dimension for each image Total of 420 training images and 492 test images Bagging repetition number : 80 15
Result Compare with state-of-the-art 16
Our-SVM w.r.t # templates 17 Analysis of bagging-based classification
Robustness to non-accurate object locations 18
Conclusion A codebook-free and annotation-free fine-grained By image template matching Bagging-based method Deal with redundant and noisy large-dimensional features. 19