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Author Diego Velazquez; Pau Rodriguez; Alexandre Lacoste; Issam H. Laradji; Xavier Roca; Jordi Gonzalez edit  url
openurl 
  Title (up) Evaluating Counterfactual Explainers Type Journal
  Year 2023 Publication Transactions on Machine Learning Research Abbreviated Journal TMLR  
  Volume Issue Pages  
  Keywords Explainability; Counterfactuals; XAI  
  Abstract Explainability methods have been widely used to provide insight into the decisions made by statistical models, thus facilitating their adoption in various domains within the industry. Counterfactual explanation methods aim to improve our understanding of a model by perturbing samples in a way that would alter its response in an unexpected manner. This information is helpful for users and for machine learning practitioners to understand and improve their models. Given the value provided by counterfactual explanations, there is a growing interest in the research community to investigate and propose new methods. However, we identify two issues that could hinder the progress in this field. (1) Existing metrics do not accurately reflect the value of an explainability method for the users. (2) Comparisons between methods are usually performed with datasets like CelebA, where images are annotated with attributes that do not fully describe them and with subjective attributes such as ``Attractive''. In this work, we address these problems by proposing an evaluation method with a principled metric to evaluate and compare different counterfactual explanation methods. The evaluation method is based on a synthetic dataset where images are fully described by their annotated attributes. As a result, we are able to perform a fair comparison of multiple explainability methods in the recent literature, obtaining insights about their performance. We make the code public for the benefit of the research community.  
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  Notes ISE Approved no  
  Call Number Admin @ si @ VRL2023 Serial 3891  
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Author Ivan Huerta; Ariel Amato; Xavier Roca; Jordi Gonzalez edit   pdf
doi  openurl
  Title (up) Exploiting Multiple Cues in Motion Segmentation Based on Background Subtraction Type Journal Article
  Year 2013 Publication Neurocomputing Abbreviated Journal NEUCOM  
  Volume 100 Issue Pages 183–196  
  Keywords Motion segmentation; Shadow suppression; Colour segmentation; Edge segmentation; Ghost detection; Background subtraction  
  Abstract This paper presents a novel algorithm for mobile-object segmentation from static background scenes, which is both robust and accurate under most of the common problems found in motionsegmentation. In our first contribution, a case analysis of motionsegmentation errors is presented taking into account the inaccuracies associated with different cues, namely colour, edge and intensity. Our second contribution is an hybrid architecture which copes with the main issues observed in the case analysis by fusing the knowledge from the aforementioned three cues and a temporal difference algorithm. On one hand, we enhance the colour and edge models to solve not only global and local illumination changes (i.e. shadows and highlights) but also the camouflage in intensity. In addition, local information is also exploited to solve the camouflage in chroma. On the other hand, the intensity cue is applied when colour and edge cues are not available because their values are beyond the dynamic range. Additionally, temporal difference scheme is included to segment motion where those three cues cannot be reliably computed, for example in those background regions not visible during the training period. Lastly, our approach is extended for handling ghost detection. The proposed method obtains very accurate and robust motionsegmentation results in multiple indoor and outdoor scenarios, while outperforming the most-referred state-of-art approaches.  
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  Publisher Elsevier Place of Publication Editor  
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  Notes ISE Approved no  
  Call Number Admin @ si @ HAR2013 Serial 1808  
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Author Josep M. Gonfaus; Marco Pedersoli; Jordi Gonzalez; Andrea Vedaldi; Xavier Roca edit   pdf
doi  openurl
  Title (up) Factorized appearances for object detection Type Journal Article
  Year 2015 Publication Computer Vision and Image Understanding Abbreviated Journal CVIU  
  Volume 138 Issue Pages 92–101  
  Keywords Object recognition; Deformable part models; Learning and sharing parts; Discovering discriminative parts  
  Abstract Deformable object models capture variations in an object’s appearance that can be represented as image deformations. Other effects such as out-of-plane rotations, three-dimensional articulations, and self-occlusions are often captured by considering mixture of deformable models, one per object aspect. A more scalable approach is representing instead the variations at the level of the object parts, applying the concept of a mixture locally. Combining a few part variations can in fact cheaply generate a large number of global appearances.

A limited version of this idea was proposed by Yang and Ramanan [1], for human pose dectection. In this paper we apply it to the task of generic object category detection and extend it in several ways. First, we propose a model for the relationship between part appearances more general than the tree of Yang and Ramanan [1], which is more suitable for generic categories. Second, we treat part locations as well as their appearance as latent variables so that training does not need part annotations but only the object bounding boxes. Third, we modify the weakly-supervised learning of Felzenszwalb et al. and Girshick et al. [2], [3] to handle a significantly more complex latent structure.
Our model is evaluated on standard object detection benchmarks and is found to improve over existing approaches, yielding state-of-the-art results for several object categories.
 
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  Notes ISE; 600.063; 600.078 Approved no  
  Call Number Admin @ si @ GPG2015 Serial 2705  
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Author Ana Garcia Rodriguez; Yael Tudela; Henry Cordova; S. Carballal; I. Ordas; L. Moreira; E. Vaquero; O. Ortiz; L. Rivero; F. Javier Sanchez; Miriam Cuatrecasas; Maria Pellise; Jorge Bernal; Gloria Fernandez Esparrach edit  doi
openurl 
  Title (up) First in Vivo Computer-Aided Diagnosis of Colorectal Polyps using White Light Endoscopy Type Journal Article
  Year 2022 Publication Endoscopy Abbreviated Journal END  
  Volume 54 Issue Pages  
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  Address 2022/04/14  
  Corporate Author Thesis  
  Publisher Georg Thieme Verlag KG Place of Publication Editor  
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  Notes ISE Approved no  
  Call Number Admin @ si @ GTC2022a Serial 3746  
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Author Parichehr Behjati Ardakani; Pau Rodriguez; Carles Fernandez; Armin Mehri; Xavier Roca; Seiichi Ozawa; Jordi Gonzalez edit  doi
openurl 
  Title (up) Frequency-based Enhancement Network for Efficient Super-Resolution Type Journal Article
  Year 2022 Publication IEEE Access Abbreviated Journal ACCESS  
  Volume 10 Issue Pages 57383-57397  
  Keywords Deep learning; Frequency-based methods; Lightweight architectures; Single image super-resolution  
  Abstract Recently, deep convolutional neural networks (CNNs) have provided outstanding performance in single image super-resolution (SISR). Despite their remarkable performance, the lack of high-frequency information in the recovered images remains a core problem. Moreover, as the networks increase in depth and width, deep CNN-based SR methods are faced with the challenge of computational complexity in practice. A promising and under-explored solution is to adapt the amount of compute based on the different frequency bands of the input. To this end, we present a novel Frequency-based Enhancement Block (FEB) which explicitly enhances the information of high frequencies while forwarding low-frequencies to the output. In particular, this block efficiently decomposes features into low- and high-frequency and assigns more computation to high-frequency ones. Thus, it can help the network generate more discriminative representations by explicitly recovering finer details. Our FEB design is simple and generic and can be used as a direct replacement of commonly used SR blocks with no need to change network architectures. We experimentally show that when replacing SR blocks with FEB we consistently improve the reconstruction error, while reducing the number of parameters in the model. Moreover, we propose a lightweight SR model — Frequency-based Enhancement Network (FENet) — based on FEB that matches the performance of larger models. Extensive experiments demonstrate that our proposal performs favorably against the state-of-the-art SR algorithms in terms of visual quality, memory footprint, and inference time. The code is available at https://github.com/pbehjatii/FENet  
  Address 18 May 2022  
  Corporate Author Thesis  
  Publisher IEEE Place of Publication Editor  
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  Notes ISE Approved no  
  Call Number Admin @ si @ BRF2022a Serial 3747  
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