Luiz Gustavo Hafemann

Luiz Gustavo Hafemann

Computer Vision Researcher

About Me

Computer Vision Researcher with 8 years of experience in modeling machine learning problems for computer vision, including image classification, video activity recognition and object detection. Published 13 articles in conferences and journals (1k+ citations on Google scholar), including top tier venues such as CVPR and IEEE Transactions on Information Forensic and Security. Strong skills in error analysis, tailoring problem formulations for specific tasks, building vision datasets from multiple sources of data, and developing solutions with production constraints in mind.

I obtained my Ph.D. from ÉTS Montreal in 2019. My research was focused on the biometric task of Offline Handwritten Signature Verification. I also have a master's in Computer Science, in which I explored Deep Learning models for Texture Classification. I participated in the 2017 and 2018 NIPS competition on adversarial attacks/defenses, and my team got 1st place on the "Untargeted attacks" track in the 2018 edition. I also participated in two editions of the Deep Learning Summer School organized by the MILA lab (in 2015 and 2016).

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Publications

Journal Papers

Cruz, R., Hafemann, L., Sabourin, R., Cavalcanti, G. "DESlib: A Dynamic ensemble selection library in Python", Journal of Machine Learning Research, 2020. paper, preprint code

Hafemann, L., Sabourin, R., Oliveira, L. "Meta-learning for fast classifier adaptation to new users of Signature Verification systems", IEEE Transactions on Information Forensics and Security , 2019. paper, preprint code

Hafemann, L., Sabourin, R., Oliveira, L. "Characterizing and evaluating adversarial examples for Offline Handwritten Signature Verification", IEEE Transactions on Information Forensics and Security , 2019. paper, preprint code

Hafemann, L., Sabourin, R., Oliveira, L. "Fixed-sized representation learning from Offline Handwritten Signatures of different sizes", International Journal on Document Analysis and Recognition (IJDAR), 2018. paper, preprint code

Hafemann, L., Sabourin, R., Oliveira, L. "Learning Features for Offline Handwritten Signature Verification using Deep Convolutional Neural Networks", Pattern Recognition, 2017. paper, preprint code

Conference Papers

Liu Y., Hafemann, L.A Scale-Invariant Trajectory Simplification Method for Efficient Data Collection in Videos", 9th International Workshop on Computer Vision in Sports at CVPR (CVPRW), 2023. link code

Liu Y., Hafemann, L., Jamieson, M., Javan, M. "Detecting and Matching Related Objects with One Proposal Multiple Predictions", 7th International Workshop on Computer Vision in Sports at CVPR (CVPRW), 2021. link

Sanford, R.*, Gorji, S.*, Hafemann, L.* Pourbabaee, B., Javan, M. "Group Activity Detection from Trajectory and Video Data in Soccer", 6th International Workshop on Computer Vision in Sports at CVPR (CVPRW), 2020. link

Rony, J.*, Hafemann, L.*, Oliveira, L., Ben Ayed, I., Sabourin, R., Granger, E. "Decoupling Direction and Norm for Efficient Gradient-Based L2 Adversarial Attacks and Defenses", Conference on Computer Vision and Pattern Recognition (CVPR oral presentation), 2019. link code

Hafemann, L., Sabourin, R., Oliveira, L., "Offline Handwritten Signature Verification - Literature Review", International Conference on Image Processing Theory, Tools and Applications (IPTA), 2017. link

Hafemann, L., Oliveira, L., Sabourin, R. "Analyzing features learned for Offline Signature Verification using Deep CNNs", International Conference on Pattern Recognition (ICPR), 2016. link

Hafemann, L., Oliveira, L., Sabourin, R. "Writer-independent Feature Learning for Offline Signature Verification using Deep Convolutional Neural Networks", International Joint Conference on Neural Networks (IJCNN), 2016. link

Hafemann, L., Cavalin, P., Oliveira, L., Sabourin, R. "Transferring Learning between Texture Classification Tasks using Convolutional Neural Networks", International Joint Conference on Neural Networks (IJCNN), 2015. link

Hafemann, L., Cavalin, P., Oliveira, L. "Forest Species Recognition using Deep Convolutional Neural Networks". 22nd International Conference on Pattern Recognition (ICPR), 2014. link

* Equal contribution

Thesis

Hafemann, L. "Learning features for offline handwritten signature verification", Ph.D. thesis, Systems Engineering Department, École de technologie supérieure, 2019. link, pdf

Hafemann, L. "An Analysis of Deep Neural Networks for Texture Classification", Master's thesis, Department of Informatics, Federal University of Paraná, 2014. link, pdf

Preprints

Abdoli, S., Hafemann, L., Rony, J., Ben Ayed, I., Cardinal, P., Koerich, A. "Universal Adversarial Audio Perturbations" preprint