1. A Codebook-Free and Annotation-free Approach for Fine-Grained Image Categorization Authors Bangpeng Yao et al. Presenter Hyung-seok Lee ( 이형석 ) CVPR 2012

2. 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

3. Related Work (1) Codebook-based approach Encoding local image patches to visual codewords Large loss of finer details important for Fine-grained 3

4. 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.

5. Overview 5 Template Matching Feature response map Novel bagging-based algorithm 1. Feature Extraction 2. Feature Representation 3. Classification

6. Template Matching Generate a large number of templates by randomly sampling rectangular regions from all training images 6

7. Input image is represented by the response score of matching it self with each of the template It can captures the subtle distinctions 7

8. Feature representation 8 1 step : Three-largest response score 2 step : Largest score on each region

9. 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

10. Bagging Based Classification 10 Motivation Large # of template  high dimensional feature It provide richer image representation & capture more subtle visual distinction

11. 11 But over-complete & non-discriminative element Conventional classification such as single SVM suffer from overfitting

12. 12 Traditional bagging method Randomly select element from image feature vector Aggregating set of classifiers Ref : http://cse-wiki.unl.edu/wiki/index.php/Bagging_and_Boosting Model averaging Avoid overfitting

13. 13 Novel bagging-based algorithm Full usage of available template matching results

14. 14 Guarantees that the correlation between the classifiers are small C : Regularization T : Correlation tolerance

15. 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 : 0.75 1 1.3 420 x 100 x 3 x 7 = 882000 dimension for each image Total of 420 training images and 492 test images Bagging repetition number : 80 15

16. Result Compare with state-of-the-art 16

17. Our-SVM w.r.t # templates 17 Analysis of bagging-based classification

18. Robustness to non-accurate object locations 18

19. 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