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Dimosthenis Karatzas

dblp:03/6509 · also Dimosthenis A. Karatzas · DBLP profile ↗
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121ranked-venue papers
10as first author
47since 2021 · last 2026
0000-0001-8762-4454ORCID · verified

Domains — the database's venue-derived domains; a paper can count in several

Artificial intelligence and machine learning · 85 · 6 first-author · 33 since 2021Databases, data management, data science and information retrieval · 70 · 8 first-author · 24 since 2021Graphics, computer vision, multimedia, augmented reality and games · 31 · 1 first-author · 15 since 2021Systems, architecture and hardware · 1

Expertise — from the expertise taxonomy: the topics of the expert's papers under the CCF categories. A weight counts papers with recency: 1 for a paper about the topic, 0.3 when the topic is its context, halved every five years.

Artificial intelligence
11 papers
Vision and language · 52% Trustworthy machine learning · 18% Image recognition and object detection · 11%
Computer graphics and multimedia
4 papers
Image and video processing · 51% Multimedia analysis and retrieval · 40% Visual content generation and editing · 8%
Databases, data mining, and information retrieval
2 papers
Information retrieval · 100%
Network and information security
1 paper
Security and privacy of machine learning · 77% Privacy and data protection · 23%

Topics — the 28 heaviest of 34, each with the papers that count most for it

TopicWeightPapersLastEvidence papers
Computer vision › Vision and language › visual question answering
document visual question answering
1.722025
DocVXQA: Context-Aware Visual Explanations for Document Question Answering · ICML 2025
DocMIA: Document-Level Membership Inference Attacks against DocVQA Models · ICLR 2025
Computer vision › Vision and language
visual question answering
1.222025
DocMIA: Document-Level Membership Inference Attacks against DocVQA Models · ICLR 2025
Scene Text Visual Question Answering · ICCV 2019
Computer vision › Vision and language
image captioning
1.022023
Show, Interpret and Tell: Entity-Aware Contextualised Image Captioning in Wikipedia · AAAI 2023
Good News, Everyone! Context Driven Entity-Aware Captioning for News Images · CVPR 2019
Machine learning › Trustworthy machine learning
interpretability
0.912025
DocVXQA: Context-Aware Visual Explanations for Document Question Answering · ICML 2025
Machine learning › Trustworthy machine learning › interpretability
visual explanation
0.912025
DocVXQA: Context-Aware Visual Explanations for Document Question Answering · ICML 2025
Security and privacy of machine learning
membership inference
0.912025
DocMIA: Document-Level Membership Inference Attacks against DocVQA Models · ICLR 2025
Multimedia analysis and retrieval › multimedia analysis
comic analysis
0.812024
CoMix: A Comprehensive Benchmark for Multi-Task Comic Understanding · NeurIPS 2024
Multimedia analysis and retrieval › multimedia analysis
multimodal reasoning
0.812024
CoMix: A Comprehensive Benchmark for Multi-Task Comic Understanding · NeurIPS 2024
Natural language and speech › Information extraction and text analysis
named entity recognition
0.712023
Show, Interpret and Tell: Entity-Aware Contextualised Image Captioning in Wikipedia · AAAI 2023
Image and video processing
document image analysis
0.712023
Text-DIAE: A Self-Supervised Degradation Invariant Autoencoder for Text Recognition and Document Enhancement · AAAI 2023
Image and video processing › image enhancement
document image enhancement
0.712023
Text-DIAE: A Self-Supervised Degradation Invariant Autoencoder for Text Recognition and Document Enhancement · AAAI 2023
Image and video processing
image enhancement
0.712023
Text-DIAE: A Self-Supervised Degradation Invariant Autoencoder for Text Recognition and Document Enhancement · AAAI 2023
Image and video processing › document image analysis
text recognition
0.712023
Text-DIAE: A Self-Supervised Degradation Invariant Autoencoder for Text Recognition and Document Enhancement · AAAI 2023
Robotics › Autonomous driving
perception
0.412020
RoadText-1K: Text Detection & Recognition Dataset for Driving Videos · ICRA 2020
Computer vision › Image recognition and object detection
scene text spotting
0.412020
RoadText-1K: Text Detection & Recognition Dataset for Driving Videos · ICRA 2020
Information retrieval › multimedia analysis and retrieval
image annotation
0.412020
Location Sensitive Image Retrieval and Tagging · ECCV (16) 2020
Multimedia analysis and retrieval
image retrieval
0.412020
Retrieval Guided Unsupervised Multi-domain Image to Image Translation · ACM Multimedia 2020
Visual content generation and editing
image-to-image translation
0.412020
Retrieval Guided Unsupervised Multi-domain Image to Image Translation · ACM Multimedia 2020
Computer vision › Vision and language › image captioning › fine-grained image captioning
entity-aware captioning
0.412019
Good News, Everyone! Context Driven Entity-Aware Captioning for News Images · CVPR 2019
Computer vision › Vision and language › visual question answering
text-based visual question answering
0.412019
Scene Text Visual Question Answering · ICCV 2019
Computer vision › Image recognition and object detection
scene text detection
0.312018
Single Shot Scene Text Retrieval · ECCV (14) 2018
Information retrieval › image retrieval › text-based image retrieval
scene text retrieval
0.312018
Single Shot Scene Text Retrieval · ECCV (14) 2018
Machine learning › Representation and self-supervised learning › representation learning › visual representation learning
visual feature learning
0.312017
Self-Supervised Learning of Visual Features through Embedding Images into Text Topic Spaces · CVPR 2017
Computer vision › Vision and language › cross-modal alignment
visual-semantic embedding
0.312017
Self-Supervised Learning of Visual Features through Embedding Images into Text Topic Spaces · CVPR 2017
Computer vision › Image recognition and object detection
object detection
0.212024
CoMix: A Comprehensive Benchmark for Multi-Task Comic Understanding · NeurIPS 2024
Multimedia analysis and retrieval
video dataset
0.112020
RoadText-1K: Text Detection & Recognition Dataset for Driving Videos · ICRA 2020
Natural language and speech › Information extraction and text analysis › document analysis
news analysis
0.112019
Good News, Everyone! Context Driven Entity-Aware Captioning for News Images · CVPR 2019
Computer vision › Image recognition and object detection
scene text recognition
0.112019
Scene Text Visual Question Answering · ICCV 2019

Methods — techniques the papers use, named apart from their topics

membership inference · 1.7zero-shot evaluation · 1.5fine-tuning · 1.5transformer · 1.3pretext task · 1.3contrastive learning · 1.3human evaluation · 0.9heatmap · 0.9multimodal pretraining · 0.7masked named entity modeling · 0.7text tracking · 0.4text recognition · 0.4text detection · 0.4multimodal embedding · 0.4image retrieval · 0.4disentangled representation learning · 0.4single-shot detection · 0.3
YearPublicationVenuePosition
2026 Reading in the Dark: Low-Light Scene Text Recognition
Xuanshuo Fu, Lei Kang 0002, Ernest Valveny, Dimosthenis Karatzas, Javier Vazquez-Corral
ICPR (11)4
2026 Learning Quantifiable Visual Explanations Without Ground-Truth
Andrey Barsky, Mohamed Ali Souibgui, Ernest Valveny, Dimosthenis Karatzas
ICPR (9)5
2026 Preserving privacy without compromising accuracy: Machine unlearning for handwritten text recognition
abstract
• Encoder-only Transformer baseline for handwriting text recognition (HTR). • Added writer-style head tracks & controls user-identifiable memorization. • Neural-activation pruning removes writer clues while preserving HTR accuracy. • Writer-ID Confusion (WIC) enforces uniform IDs, boosting efficient machine unlearning. • Membership-inference tests confirm privacy gains without costly retraining. Handwritten Text Recognition (HTR) is crucial for document digitization, but handwritten data can contain user-identifiable features, like unique writing styles, posing privacy risks. Regulations such as the “right to be forgotten” require models to remove these sensitive traces without full retraining. We introduce a practical encoder-only transformer baseline as a robust reference for future HTR research. Building on this, we propose a two-stage unlearning framework for multihead transformer HTR models. Our method combines neural pruning with machine unlearning applied to a writer classification head, ensuring sensitive information is removed while preserving the recognition head. We also present Writer-ID Confusion (WIC), a method that forces the forget set to follow a uniform distribution over writer identities, unlearning user-specific cues while maintaining text recognition performance. We compare WIC to Random Labeling, Fisher Forgetting, Amnesiac Unlearning, and DELETE within our prune-unlearn pipeline and consistently achieve better privacy and accuracy trade-offs. This is the first systematic study of machine unlearning for HTR. Using metrics such as Accuracy, Character Error Rate (CER), Word Error Rate (WER), and Membership Inference Attacks (MIA) on the IAM and CVL datasets, we demonstrate that our method achieves state-of-the-art or superior performance for effective unlearning. These experiments show that our approach effectively safeguards privacy without compromising accuracy, opening new directions for document analysis research. Our code is publicly available at https://github.com/leitro/WIC-WriterIDConfusion-MachineUnlearning .
Lei Kang 0002, Xuanshuo Fu, Lluís Gómez i Bigorda, Alicia Fornés, Ernest Valveny, Dimosthenis Karatzas
Pattern Recognit.6
2025 Position-Aware Stamp-Like Adversarial Attack for Document Classification
Lei Kang 0002, Maura Pintor, Dimosthenis Karatzas
ICDAR (4)4
2025 LLM-Driven Medical Document Analysis: Enhancing Trustworthy Pathology and Differential Diagnosis
Lei Kang 0002, Xuanshuo Fu, Oriol Ramos Terrades, Javier Vazquez-Corral, Ernest Valveny, Dimosthenis Karatzas
ICDAR (3)6
2025 ICDAR 2025 Handwritten Notes Understanding Challenge
Aniket Pal, Sanket Biswas, Alloy Das, Ayush Lodh, Priyanka Banerjee, Soumitri Chattopadhyay, Ajoy Mondal, Dimosthenis Karatzas, Josep Lladós 0001, C. V. Jawahar
ICDAR (5)8
2025 ComicsPAP: Understanding Comic Strips by Picking the Correct Panel
Emanuele Vivoli, Artemis Llabrés, Mohamed Ali Souibgui, Marco Bertini 0001, Ernest Valveny, Dimosthenis Karatzas
ICDAR (1)6
2025 DocMIA: Document-Level Membership Inference Attacks against DocVQA Models
abstract
Document Visual Question Answering (DocVQA) has introduced a new paradigm for end-to-end document understanding, and quickly became one of the standard benchmarks for multimodal LLMs. Automating document processing workflows, driven by DocVQA models, presents significant potential for many business sectors. However, documents tend to contain highly sensitive information, raising concerns about privacy risks associated with training such DocVQA models. One significant privacy vulnerability, exploited by the membership inference attack, is the possibility for an adversary to determine if a particular record was part of the model's training data. In this paper, we introduce two novel membership inference attacks tailored specifically to DocVQA models. These attacks are designed for two different adversarial scenarios: a white-box setting, where the attacker has full access to the model architecture and parameters, and a black-box setting, where only the model's outputs are available. Notably, our attacks assume the adversary lacks access to auxiliary datasets, which is more realistic in practice but also more challenging. Our unsupervised methods outperform existing state-of-the-art membership inference attacks across a variety of DocVQA models and datasets, demonstrating their effectiveness and highlighting the privacy risks in this domain.
Raouf Kerkouche, Mario Fritz, Dimosthenis Karatzas
ICLR4
2025 DocVXQA: Context-Aware Visual Explanations for Document Question Answering
abstract
We propose DocVXQA, a novel framework for visually self-explainable document question answering, where the goal is not only to produce accurate answers to questions but also to learn visual heatmaps that highlight critical regions, offering interpretable justifications for the model decision. To integrate explanations into the learning process, we quantitatively formulate explainability principles as explicit learning criteria. Unlike conventional relevance map methods that solely emphasize regions relevant to the answer, our context-aware DocVXQA delivers explanations that are contextually sufficient yet representation-efficient. This fosters user trust while achieving a balance between predictive performance and interpretability in document visual question answering applications. Extensive experiments, including human evaluation, provide strong evidence supporting the effectiveness of our method.
Mohamed Ali Souibgui, Changkyu Choi, Andrey Barsky, Kangsoo Jung, Ernest Valveny, Dimosthenis Karatzas
ICML6
2025 AVIR: Adaptive Visual In-Document Retrieval for Efficient Multi-Page Document Question Answering
abstract
Multi‑page Document Visual Question Answering (MP‑DocVQA) remains challenging because long documents not only strain computational resources but also reduce the effectiveness of the attention mechanism in large vision–language models (LVLMs). We tackle these issues with an Adaptive Visual In‑document Retrieval (AVIR) framework. A lightweight retrieval model first scores each page for question relevance. Pages are then clustered according to the score distribution to adaptively select relevant content. The clustered pages are screened again by Top-K to keep the context compact. However, for short documents, clustering reliability decreases, so we use a relevance probability threshold to select pages. The selected pages alone are fed to a frozen LVLM for answer generation, eliminating the need for model fine‑tuning. The proposed AVIR framework reduces the average page count required for question answering by 70%, while achieving an ANLS of 84.58% on the MP-DocVQA dataset—surpassing previous methods with significantly lower computational cost. The effectiveness of the proposed AVIR is also verified on the SlideVQA and DUDE benchmarks. Our code will be made publicly available upon acceptance.
Zongmin Li, Yachuan Li, Lei Kang 0002, Dimosthenis Karatzas, Wenkang Ma
MMAsia4
2025 Special issue on advanced topics in document analysis (2025 ICDAR-IJDAR journal track)
Daniel P. Lopresti, Dimosthenis Karatzas, Xu-Cheng Yin
Int. J. Document Anal. Recognit.2
2024 Multi-page Document VQA with Recurrent Memory Transformer
Lei Kang 0002, Dimosthenis Karatzas
DAS3
2024 Image-Text Matching for Large-Scale Book Collections
Artemis Llabrés, Arka Ujjal Dey, Dimosthenis Karatzas, Ernest Valveny
DAS3
2024 GRIF-DM: Generation of Rich Impression Fonts Using Diffusion Models
abstract
Fonts are integral to creative endeavors, design processes, and artistic productions. The appropriate selection of a font can significantly enhance artwork and endow advertisements with a higher level of expressivity. Despite the availability of numerous diverse font designs online, traditional retrieval-based methods for font selection are increasingly being supplanted by generation-based approaches. These newer methods offer enhanced flexibility, catering to specific user preferences and capturing unique stylistic impressions. However, current impression font techniques based on Generative Adversarial Networks (GANs) necessitate the utilization of multiple auxiliary losses to provide guidance during generation. Furthermore, these methods commonly employ weighted summation for the fusion of impression-related keywords. This leads to generic vectors with the addition of more impression keywords, ultimately lacking in detail generation capacity. In this paper, we introduce a diffusion-based method, termed GRIF-DM, to generate fonts that vividly embody specific impressions, utilizing an input consisting of a single letter and a set of descriptive impression keywords. The core innovation of GRIF-DM lies in the development of dual cross-attention modules, which process the characteristics of the letters and impression keywords independently but synergistically, ensuring effective integration of both types of information. Our experimental results, conducted on the MyFonts dataset, affirm that this method is capable of producing realistic, vibrant, and high-fidelity fonts that are closely aligned with user specifications. This confirms the potential of our approach to revolutionize font generation by accommodating a broad spectrum of user-driven design requirements. Our code is publicly available at https://github.com/leitro/GRIF-DM.
Lei Kang 0002, Fei Yang 0004, Kai Wang 0060, Mohamed Ali Souibgui, Lluís Gómez i Bigorda, Alicia Fornés, Ernest Valveny, Dimosthenis Karatzas
ECAI8
2024 Machine Unlearning for Document Classification
Lei Kang 0002, Mohamed Ali Souibgui, Fei Yang 0004, Lluís Gómez i Bigorda, Ernest Valveny, Dimosthenis Karatzas
ICDAR (4)6
2024 Multi-page Document Visual Question Answering Using Self-attention Scoring Mechanism
Lei Kang 0002, Rubèn Tito, Ernest Valveny, Dimosthenis Karatzas
ICDAR (6)4
2024 Federated Document Visual Question Answering: A Pilot Study
Dimosthenis Karatzas
ICDAR (6)2
2024 Privacy-Aware Document Visual Question Answering
Rubèn Tito, Marlon Tobaben, Raouf Kerkouche, Mohamed Ali Souibgui, Kangsoo Jung, Joonas Jälkö, Vincent Poulain D'Andecy, Aurélie Joseph, Lei Kang 0002, Ernest Valveny, Antti Honkela, Mario Fritz, Dimosthenis Karatzas
ICDAR (6)14
2024 Multimodal Transformer for Comics Text-Cloze
Emanuele Vivoli, Joan Lafuente Baeza, Ernest Valveny, Dimosthenis Karatzas
ICDAR (6)4
2024 Counting the Corner Cases: Revisiting Robust Reading Challenge Data Sets, Evaluation Protocols, and Metrics
Jerod J. Weinman, Amelia Gómez Grabowska, Dimosthenis Karatzas
ICDAR (4)3
2024 CoMix: A Comprehensive Benchmark for Multi-Task Comic Understanding
abstract
The comic domain is rapidly advancing with the development of single-page analysis and synthesis models. However, evaluation metrics and datasets lag behind, often limited to small-scale or single-style test sets. We introduce a novel benchmark, CoMix, designed to evaluate the multi-task capabilities of models in comic analysis. Unlike existing benchmarks that focus on isolated tasks such as object detection or text recognition, CoMix addresses a broader range of tasks including object detection, speaker identification, character re-identification, reading order, and multi-modal reasoning tasks like character naming and dialogue generation. Our benchmark comprises three existing datasets with expanded annotations to support multi-task evaluation. To mitigate the over-representation of manga-style data, we have incorporated a new dataset of carefully selected American comic-style books, thereby enriching the diversity of comic styles. CoMix is designed to assess pre-trained models in zero-shot and limited fine-tuning settings, probing their transfer capabilities across different comic styles and tasks. The validation split of the benchmark is publicly available for research purposes, and an evaluation server for the held-out test split is also provided. Comparative results between human performance and state-of-the-art models reveal a significant performance gap, highlighting substantial opportunities for advancements in comic understanding. The dataset, baseline models, and code are accessible at https://github.com/emanuelevivoli/CoMix-dataset. This initiative sets a new standard for comprehensive comic analysis, providing the community with a common benchmark for evaluation on a large and varied set.
Emanuele Vivoli, Marco Bertini 0001, Dimosthenis Karatzas
NeurIPS3
2024 STEP - Towards Structured Scene-Text Spotting
abstract
We introduce the structured scene-text spotting task, which requires a scene-text OCR system to spot text in the wild according to a query regular expression. Contrary to generic scene-text OCR, structured scene-text spotting seeks to dynamically condition both detection and recognition on user-provided regular expressions. To tackle this task, we propose the Structured TExt sPotter (STEP), a model that exploits the provided text structure to guide the OCR process. STEP is able to deal with regular expressions that contain spaces and it is not bound to detection at wordlevel granularity. Our approach enables accurate zero-shot structured text spotting in a wide variety of real-world reading scenarios and is solely trained on publicly available data. To demonstrate the effectiveness of our approach, we introduce a new challenging test dataset that contains several types of out-of-vocabulary structured text, reflecting important reading applications such as weight information, serial numbers, license plates etc. We demonstrate that STEP can provide specialized OCR performance on demand in all tested scenarios. The code and test dataset are released at https://github.com/CVC-DAG/STEP.
Sergi Garcia-Bordils, Dimosthenis Karatzas, Marçal Rusiñol
WACV2
2023 Show, Interpret and Tell: Entity-Aware Contextualised Image Captioning in Wikipedia
abstract
Humans exploit prior knowledge to describe images, and are able to adapt their explanation to specific contextual information given, even to the extent of inventing plausible explanations when contextual information and images do not match. In this work, we propose the novel task of captioning Wikipedia images by integrating contextual knowledge. Specifically, we produce models that jointly reason over Wikipedia articles, Wikimedia images and their associated descriptions to produce contextualized captions. The same Wikimedia image can be used to illustrate different articles, and the produced caption needs to be adapted to the specific context allowing us to explore the limits of the model to adjust captions to different contextual information. Dealing with out-of-dictionary words and Named Entities is a challenging task in this domain. To address this, we propose a pre-training objective, Masked Named Entity Modeling (MNEM), and show that this pretext task results to significantly improved models. Furthermore, we verify that a model pre-trained in Wikipedia generalizes well to News Captioning datasets. We further define two different test splits according to the difficulty of the captioning task. We offer insights on the role and the importance of each modality and highlight the limitations of our model.
Ali Furkan Biten, Andrés Mafla, Lluís Gómez i Bigorda, Dimosthenis Karatzas
AAAI5
2023 Text-DIAE: A Self-Supervised Degradation Invariant Autoencoder for Text Recognition and Document Enhancement
abstract
In this paper, we propose a Text-Degradation Invariant Auto Encoder (Text-DIAE), a self-supervised model designed to tackle two tasks, text recognition (handwritten or scene-text) and document image enhancement. We start by employing a transformer-based architecture that incorporates three pretext tasks as learning objectives to be optimized during pre-training without the usage of labelled data. Each of the pretext objectives is specifically tailored for the final downstream tasks. We conduct several ablation experiments that confirm the design choice of the selected pretext tasks. Importantly, the proposed model does not exhibit limitations of previous state-of-the-art methods based on contrastive losses, while at the same time requiring substantially fewer data samples to converge. Finally, we demonstrate that our method surpasses the state-of-the-art in existing supervised and self-supervised settings in handwritten and scene text recognition and document image enhancement. Our code and trained models will be made publicly available at https://github.com/dali92002/SSL-OCR
Mohamed Ali Souibgui, Sanket Biswas, Andrés Mafla, Ali Furkan Biten, Alicia Fornés, Yousri Kessentini, Josep Lladós 0001, Lluís Gómez i Bigorda, Dimosthenis Karatzas
AAAI9
2023 Accelerating Transformer-Based Scene Text Detection and Recognition via Token Pruning
Sergi Garcia-Bordils, Dimosthenis Karatzas, Marçal Rusiñol
ICDAR (6)2
2023 DocILE Benchmark for Document Information Localization and Extraction
Stepán Simsa, Milan Sulc, Michal Uricár, Ahmed Hamdi, Matej Kocián, Matyás Skalický, Jiri Matas, Antoine Doucet, Mickaël Coustaty, Dimosthenis Karatzas
ICDAR (2)11
2023 ICDAR 2023 Competition on RoadText Video Text Detection, Tracking and Recognition
George Tom, Minesh Mathew, Sergi Garcia-Bordils, Dimosthenis Karatzas, C. V. Jawahar
ICDAR (2)4
2023 Reading Between the Lanes: Text VideoQA on the Road
George Tom, Minesh Mathew, Sergi Garcia-Bordils, Dimosthenis Karatzas, C. V. Jawahar
ICDAR (6)4
2023 ICDAR 2023 Competition on Video Text Reading for Dense and Small Text
Weijia Wu 0001, Yuzhong Zhao, Zhuang Li 0002, Zheng Shou 0001, Umapada Pal 0001, Dimosthenis Karatzas, Xiang Bai
ICDAR (2)7
2023 ICDAR 2023 Competition on Reading the Seal Title
Wenwen Yu, Mingrui Chen 0001, Ning Lu 0003, Yinlong Wen, Dimosthenis Karatzas, Xiang Bai
ICDAR (2)7
2023 ICDAR 2023 Competition on Structured Text Extraction from Visually-Rich Document Images
Wenwen Yu, Chengquan Zhang, Haoyu Cao 0001, Wei Hua 0005, Bohan Li 0010, Mingrui Chen 0001, Jianfeng Kuang, Mengjun Cheng, Yuning Du, Shikun Feng, Xiaoguang Hu, Pengyuan Lv, Yuechen Yu, Wanxiang Che, Errui Ding, Cheng-Lin Liu 0001, Jiebo Luo 0001, Shuicheng Yan, Min Zhang 0005, Dimosthenis Karatzas, Xing Sun 0001, Jingdong Wang 0001, Xiang Bai
ICDAR (2)24
2023 Watching the News: Towards VideoQA Models that can Read
abstract
Video Question Answering methods focus on common-sense reasoning and visual cognition of objects or persons and their interactions over time. Current VideoQA approaches ignore the textual information present in the video. Instead, we argue that textual information is complementary to the action and provides essential contextualisation cues to the reasoning process. To this end, we propose a novel VideoQA task that requires reading and understanding the text in the video. To explore this direction, we focus on news videos and require QA systems to comprehend and answer questions about the topics presented by combining visual and textual cues in the video. We introduce the "NewsVideoQA" dataset that comprises more than 8, 600 QA pairs on 3, 000+ news videos obtained from diverse news channels from around the world. We demonstrate the limitations of current Scene Text VQA and VideoQA methods and propose ways to incorporate scene text information into VideoQA methods.
Soumya Jahagirdar, Minesh Mathew, Dimosthenis Karatzas, C. V. Jawahar
WACV3
2023 Hierarchical multimodal transformers for Multipage DocVQA
Rubèn Tito, Dimosthenis Karatzas, Ernest Valveny
Pattern Recognit.2
2022 Read While You Drive - Multilingual Text Tracking on the Road
Sergi Garcia-Bordils, George Tom, Sangeeth Reddy, Minesh Mathew, Marçal Rusiñol, C. V. Jawahar, Dimosthenis Karatzas
DAS7
2022 A Multilingual Approach to Scene Text Visual Question Answering
Josep Brugués i Pujolràs, Lluís Gómez i Bigorda, Dimosthenis Karatzas
DAS3
2022 Let there be a clock on the beach: Reducing Object Hallucination in Image Captioning
abstract
Explaining an image with missing or non-existent objects is known as object bias (hallucination) in image captioning. This behaviour is quite common in the state-of-the-art captioning models which is not desirable by humans. To decrease the object hallucination in captioning, we propose three simple yet efficient training augmentation method for sentences which requires no new training data or increase in the model size. By extensive analysis, we show that the proposed methods can significantly diminish our models’ object bias on hallucination metrics. Moreover, we experimentally demonstrate that our methods decrease the dependency on the visual features. All of our code, configuration files and model weights are available online1.
Ali Furkan Biten, Lluís Gómez i Bigorda, Dimosthenis Karatzas
WACV3
2022 Is An Image Worth Five Sentences? A New Look into Semantics for Image-Text Matching
abstract
The task of image-text matching aims to map representations from different modalities into a common joint visual-textual embedding. However, the most widely used datasets for this task, MSCOCO and Flickr30K, are actually image captioning datasets that offer a very limited set of relation-ships between images and sentences in their ground-truth annotations. This limited ground truth information forces us to use evaluation metrics based on binary relevance: given a sentence query we consider only one image as relevant. However, many other relevant images or captions may be present in the dataset. In this work, we propose two metrics that evaluate the degree of semantic relevance of retrieved items, independently of their annotated binary relevance. Additionally, we incorporate a novel strategy that uses an image captioning metric, CIDEr, to define a Semantic Adaptive Margin (SAM) to be optimized in a standard triplet loss. By incorporating our formulation to existing models, a large improvement is obtained in scenarios where available training data is limited. We also demonstrate that the performance on the annotated image-caption pairs is maintained while improving on other non-annotated relevant items when employing the full training set. The code for our new metric can be found at github.com/furkanbiten/ncs_metric and the model implementation at github.com/andrespmd/semantic_adaptive_margin.
Ali Furkan Biten, Andrés Mafla, Lluís Gómez i Bigorda, Dimosthenis Karatzas
WACV4
2022 InfographicVQA
abstract
Infographics communicate information using a combination of textual, graphical and visual elements. This work explores the automatic understanding of infographic images by using a Visual Question Answering technique. To this end, we present InfographicVQA, a new dataset comprising a diverse collection of infographics and question-answer annotations. The questions require methods that jointly reason over the document layout, textual content, graphical elements, and data visualizations. We curate the dataset with an emphasis on questions that require elementary reasoning and basic arithmetic skills. For VQA on the dataset, we evaluate two Transformer-based strong baselines. Both the baselines yield unsatisfactory results compared to near perfect human performance on the dataset. The results suggest that VQA on infographics—images that are designed to communicate information quickly and clearly to human brain—is ideal for benchmarking machine understanding of complex document images. The dataset is available for download at docvqa.org
Minesh Mathew, Viraj Bagal, Rubèn Tito, Dimosthenis Karatzas, Ernest Valveny, C. V. Jawahar
WACV4
2022 One-shot Compositional Data Generation for Low Resource Handwritten Text Recognition
abstract
Low resource Handwritten Text Recognition (HTR) is a hard problem due to the scarce annotated data and the very limited linguistic information (dictionaries and language models). For example, in the case of historical ciphered manuscripts, which are usually written with invented alphabets to hide the message contents. Thus, in this paper we address this problem through a data generation technique based on Bayesian Program Learning (BPL). Contrary to traditional generation approaches, which require a huge amount of annotated images, our method is able to generate human-like handwriting using only one sample of each symbol in the alphabet. After generating symbols, we create synthetic lines to train state-of-the-art HTR architectures in a segmentation free fashion. Quantitative and qualitative analyses were carried out and confirm the effectiveness of the proposed method.
Mohamed Ali Souibgui, Ali Furkan Biten, Sounak Dey, Alicia Fornés, Yousri Kessentini, Lluís Gómez i Bigorda, Dimosthenis Karatzas, Josep Lladós 0001
WACV7
2021 Document Collection Visual Question Answering
Rubèn Tito, Dimosthenis Karatzas, Ernest Valveny
ICDAR (2)2
2021 ICDAR 2021 Competition on Document Visual Question Answering
Rubèn Tito, Minesh Mathew, C. V. Jawahar, Ernest Valveny, Dimosthenis Karatzas
ICDAR (4)5
2021 Multi-Modal Reasoning Graph for Scene-Text Based Fine-Grained Image Classification and Retrieval
abstract
Scene text instances found in natural images carry explicit semantic information that can provide important cues to solve a wide array of computer vision problems. In this paper, we focus on leveraging multi-modal content in the form of visual and textual cues to tackle the task of fine-grained image classification and retrieval. First, we obtain the text instances from images by employing a text reading system. Then, we combine textual features with salient image regions to exploit the complementary information carried by the two sources. Specifically, we employ a Graph Convolutional Network to perform multi-modal reasoning and obtain relationship-enhanced features by learning a common semantic space between salient objects and text found in an image. By obtaining an enhanced set of visual and textual features, the proposed model greatly outperforms previous state-of-the-art in two different tasks, fine-grained classification and image retrieval in the Con-Text[23] and Drink Bottle[4] datasets.
Andrés Mafla, Sounak Dey, Ali Furkan Biten, Lluís Gómez i Bigorda, Dimosthenis Karatzas
WACV5
2021 StacMR: Scene-Text Aware Cross-Modal Retrieval
abstract
Recent models for cross-modal retrieval have benefited from an increasingly rich understanding of visual scenes, afforded by scene graphs and object interactions to mention a few. This has resulted in an improved matching between the visual representation of an image and the textual representation of its caption. Yet, current visual representations overlook a key aspect: the text appearing in images, which may contain crucial information for retrieval. In this paper, we first propose a new dataset that allows exploration of cross-modal retrieval where images contain scene-text instances. Then, armed with this dataset, we describe several approaches which leverage scene text, including a better scene-text aware cross-modal retrieval method which uses specialized representations for text from the captions and text from the visual scene, and reconcile them in a common embedding space. Extensive experiments confirm that cross-modal retrieval approaches benefit from scene text and highlight interesting research questions worth exploring further. Dataset and code are available at europe.naverlabs.com/stacmr.
Andrés Mafla, Rafael S. Rezende, Lluís Gómez i Bigorda, Diane Larlus, Dimosthenis Karatzas
WACV5
2021 DocVQA: A Dataset for VQA on Document Images
abstract
We present a new dataset for Visual Question Answering (VQA) on document images called DocVQA. The dataset consists of 50,000 questions defined on 12,000+ document images. Detailed analysis of the dataset in comparison with similar datasets for VQA and reading comprehension is presented. We report several baseline results by adopting existing VQA and reading comprehension models. Although the existing models perform reasonably well on certain types of questions, there is large performance gap compared to human performance (94.36% accuracy). The models need to improve specifically on questions where understanding structure of the document is crucial. The dataset, code and leaderboard are available at docvqa.org.
Minesh Mathew, Dimosthenis Karatzas, C. V. Jawahar
WACV2
2021 Asking questions on handwritten document collections
Minesh Mathew, Lluís Gómez i Bigorda, Dimosthenis Karatzas, C. V. Jawahar
Int. J. Document Anal. Recognit.3
2021 Real-time Lexicon-free Scene Text Retrieval
Andrés Mafla, Rubèn Tito, Sounak Dey, Lluís Gómez i Bigorda, Marçal Rusiñol, Ernest Valveny, Dimosthenis Karatzas
Pattern Recognit.7
2021 Multimodal grid features and cell pointers for scene text visual question answering
Lluís Gómez i Bigorda, Ali Furkan Biten, Rubèn Tito, Andrés Mafla, Marçal Rusiñol, Ernest Valveny, Dimosthenis Karatzas
Pattern Recognit. Lett.7
2020 Location Sensitive Image Retrieval and Tagging
Raul Gomez, Jaume Gibert, Lluís Gómez i Bigorda, Dimosthenis Karatzas
ECCV (16)4
2020 Text Recognition - Real World Data and Where to Find Them
abstract
We present a method for exploiting weakly annotated images to improve text extraction pipelines. The approach uses an arbitrary end-to-end text recognition system to obtain text region proposals and their, possibly erroneous, transcriptions. The method includes matching of imprecise transcriptions to weak annotations and an edit distance guided neighbourhood search. It produces nearly error-free, localised instances of scene text, which we treat as “pseudo ground truth” (PGT). The method is applied to two weakly-annotated datasets. Training with the extracted PGT consistently improves the accuracy of a state of the art recognition model, by 3.7% on average, across different benchmark datasets (image domains) and 24.5% on one of the weakly annotated datasets11Acknowledgements. The authors were supported by Czech Technical University student grant SGS20/171/0HK3/3TJ13, the MEYS VVV project CZ.02.1.01/0.010.0J16 019/0000765 Research Center for Informatics, the Spanish Research project TIN2017-89779-P and the CERCA Programme / Generalitat de Catalunya.
Klára Janousková, Jiri Matas, Lluís Gómez i Bigorda, Dimosthenis Karatzas
ICPR4
2020 RoadText-1K: Text Detection & Recognition Dataset for Driving Videos
abstract
Perceiving text is crucial to understand semantics of outdoor scenes and hence is a critical requirement to build intelligent systems for driver assistance and self-driving. Most of the existing datasets for text detection and recognition comprise still images and are mostly compiled keeping text in mind. This paper introduces a new "RoadText-1K" dataset for text in driving videos. The dataset is 20 times larger than the existing largest dataset for text in videos. Our dataset comprises 1000 video clips of driving without any bias towards text and with annotations for text bounding boxes and transcriptions in every frame. State of the art methods for text detection, recognition and tracking are evaluated on the new dataset and the results signify the challenges in unconstrained driving videos compared to existing datasets. This suggests that RoadText-1K is suited for research and development of reading systems, robust enough to be incorporated into more complex downstream tasks like driver assistance and self-driving. The dataset can be found at http://cvit.iiit.ac.in/research/projects/cvit-projects/roadtext-1k.
Sangeeth Reddy, Minesh Mathew, Lluís Gómez i Bigorda, Marçal Rusiñol, Dimosthenis Karatzas, C. V. Jawahar
ICRA5
2020 Retrieval Guided Unsupervised Multi-domain Image to Image Translation
abstract
Image to image translation aims to learn a mapping that transforms an image from one visual domain to another. Recent works assume that images descriptors can be disentangled into a domain-invariant content representation and a domain-specific style representation. Thus, translation models seek to preserve the content of source images while changing the style to a target visual domain. However, synthesizing new images is extremely challenging especially in multi-domain translations, as the network has to compose content and style to generate reliable and diverse images in multiple domains. In this paper we propose the use of an image retrieval system to assist the image-to-image translation task. First, we train an image-to-image translation model to map images to multiple domains. Then, we train an image retrieval model using real and generated images to find images similar to a query one in content but in a different domain. Finally, we exploit the image retrieval system to fine-tune the image-to-image translation model and generate higher quality images. Our experiments show the effectiveness of the proposed solution and highlight the contribution of the retrieval network, which can benefit from additional unlabeled data and help image-to-image translation models in the presence of scarce data.
Raul Gomez, Marco De Nadai, Dimosthenis Karatzas, Bruno Lepri, Nicu Sebe
ACM Multimedia4
2020 Exploring Hate Speech Detection in Multimodal Publications
abstract
In this work we target the problem of hate speech detection in multimodal publications formed by a text and an image. We gather and annotate a large scale dataset from Twitter, MMHS150K, and propose different models that jointly analyze textual and visual information for hate speech detection, comparing them with unimodal detection. We provide quantitative and qualitative results and analyze the challenges of the proposed task. We find that, even though images are useful for the hate speech detection task, current multimodal models cannot outperform models analyzing only text. We discuss why and open the field and the dataset for further research.
Raul Gomez, Jaume Gibert, Lluís Gómez i Bigorda, Dimosthenis Karatzas
WACV4
2020 Fine-grained Image Classification and Retrieval by Combining Visual and Locally Pooled Textual Features
abstract
Text contained in an image carries high-level semantics that can be exploited to achieve richer image understanding. In particular, the mere presence of text provides strong guiding content that should be employed to tackle a diversity of computer vision tasks such as image retrieval, fine-grained classification, and visual question answering. In this paper, we address the problem of fine-grained classification and image retrieval by leveraging textual information along with visual cues to comprehend the existing intrinsic relation between the two modalities. The novelty of the proposed model consists of the usage of a PHOC descriptor to construct a bag of textual words along with a Fisher Vector Encoding that captures the morphology of text. This approach provides a stronger multimodal representation for this task and as our experiments demonstrate, it achieves state-of-the-art results on two different tasks, fine-grained classification and image retrieval. The code of this model will be publicly available at1.
Andrés Mafla, Sounak Dey, Ali Furkan Biten, Lluís Gómez i Bigorda, Dimosthenis Karatzas
WACV5
2019 Good News, Everyone! Context Driven Entity-Aware Captioning for News Images
abstract
Current image captioning systems perform at a merely descriptive level, essentially enumerating the objects in the scene and their relations. Humans, on the contrary, interpret images by integrating several sources of prior knowledge of the world. In this work, we aim to take a step closer to producing captions that offer a plausible interpretation of the scene, by integrating such contextual information into the captioning pipeline. For this we focus on the captioning of images used to illustrate news articles. We propose a novel captioning method that is able to leverage contextual information provided by the text of news articles associated with an image. Our model is able to selectively draw information from the article guided by visual cues, and to dynamically extend the output dictionary to out-of-vocabulary named entities that appear in the context source. Furthermore we introduce ``GoodNews'', the largest news image captioning dataset in the literature and demonstrate state-of-the-art results.
Ali Furkan Biten, Lluís Gómez i Bigorda, Marçal Rusiñol, Dimosthenis Karatzas
CVPR4
2019 Scene Text Visual Question Answering
abstract
Current visual question answering datasets do not consider the rich semantic information conveyed by text within an image. In this work, we present a new dataset, ST-VQA, that aims to highlight the importance of exploiting high-level semantic information present in images as textual cues in the Visual Question Answering process. We use this dataset to define a series of tasks of increasing difficulty for which reading the scene text in the context provided by the visual information is necessary to reason and generate an appropriate answer. We propose a new evaluation metric for these tasks to account both for reasoning errors as well as shortcomings of the text recognition module. In addition we put forward a series of baseline methods, which provide further insight to the newly released dataset, and set the scene for further research.
Ali Furkan Biten, Rubèn Tito, Andrés Mafla, Lluís Gómez i Bigorda, Marçal Rusiñol, C. V. Jawahar, Ernest Valveny, Dimosthenis Karatzas
ICCV8
2019 Can One Deep Learning Model Learn Script-Independent Multilingual Word-Spotting?
abstract
Word spotting has gained increased attention lately as it can be used to extract textual information from handwritten documents and scene-text images. Current word spotting approaches are designed to work on a single language and/or script. Building intelligent models that learn script-independent multilingual word-spotting is challenging due to the large variability of multilingual alphabets and symbols. We used ResNet-152 and the Pyramidal Histogram of Characters (PHOC) embedding to build a one-model script-independent multilingual word-spotting and we tested it on Latin, Arabic, and Bangla (Indian) languages. The one-model we propose performs on par with the multi-model language-specific word-spotting system, and thus, reduces the number of models needed for each script and/or language.
Mohammed Al-Rawi, Ernest Valveny, Dimosthenis Karatzas
ICDAR3
2019 ICDAR 2019 Competition on Scene Text Visual Question Answering
abstract
This paper presents final results of ICDAR 2019 Scene Text Visual Question Answering competition (ST-VQA). ST-VQA introduces an important aspect that is not addressed by any Visual Question Answering system up to date, namely the incorporation of scene text to answer questions asked about an image. The competition introduces a new dataset comprising 23,038 images annotated with 31,791 question / answer pairs where the answer is always grounded on text instances present in the image. The images are taken from 7 different public computer vision datasets, covering a wide range of scenarios. The competition was structured in three tasks of increasing difficulty, that require reading the text in a scene and understanding it in the context of the scene, to correctly answer a given question. A novel evaluation metric is presented, which elegantly assesses both key capabilities expected from an optimal model: text recognition and image understanding. A detailed analysis of results from different participants is showcased, which provides insight into the current capabilities of VQA systems that can read. We firmly believe the dataset proposed in this challenge will be an important milestone to consider towards a path of more robust and general models that can exploit scene text to achieve holistic image understanding.
Ali Furkan Biten, Rubèn Tito, Andrés Mafla, Lluís Gómez i Bigorda, Marçal Rusiñol, Minesh Mathew, C. V. Jawahar, Ernest Valveny, Dimosthenis Karatzas
ICDAR9
2019 ICDAR2019 Robust Reading Challenge on Arbitrary-Shaped Text - RRC-ArT
abstract
This paper reports the ICDAR2019 Robust Reading Challenge on Arbitrary-Shaped Text - RRC-ArT that consists of three major challenges: i) scene text detection, ii) scene text recognition, and iii) scene text spotting. A total of 78 submissions from 46 unique teams/individuals were received for this competition. The top performing score of each challenge is as follows: i) T1 - 82.65%, ii) T2.1 - 74.3%, iii) T2.2 - 85.32%, iv) T3.1 - 53.86%, and v) T3.2 - 54.91%. Apart from the results, this paper also details the ArT dataset, tasks description, evaluation metrics and participants' methods. The dataset, the evaluation kit as well as the results are publicly available at the challenge website.
Chee Kheng Chng, Errui Ding, Jingtuo Liu, Dimosthenis Karatzas, Chee Seng Chan, Yipeng Sun, Chun Chet Ng, Canjie Luo, Zihan Ni, ChuanMing Fang, Shuaitao Zhang, Junyu Han
ICDAR4
2019 Selective Style Transfer for Text
abstract
This paper explores the possibilities of image style transfer applied to text maintaining the original transcriptions. Results on different text domains (scene text, machine printed text and handwritten text) and cross-modal results demonstrate that this is feasible, and open different research lines. Furthermore, two architectures for selective style transfer, which means transferring style to only desired image pixels, are proposed. Finally, scene text selective style transfer is evaluated as a data augmentation technique to expand scene text detection datasets, resulting in a boost of text detectors performance. Our implementation of the described models is publicly available.
Raul Gomez, Ali Furkan Biten, Lluís Gómez i Bigorda, Jaume Gibert, Dimosthenis Karatzas, Marçal Rusiñol
ICDAR5
2019 ICDAR2019 Competition on Scanned Receipt OCR and Information Extraction
abstract
The ICDAR 2019 Challenge on "Scanned receipts OCR and key information extraction" (SROIE) covers important aspects related to the automated analysis of scanned receipts. The SROIE tasks play a key role in many document analysis systems and hold significant commercial potential. Although a lot of work has been published over the years on administrative document analysis, the community has advanced relatively slowly, as most datasets have been kept private. One of the key contributions of SROIE to the document analysis community is to offer a first, standardized dataset of 1000 whole scanned receipt images and annotations, as well as an evaluation procedure for such tasks. The Challenge is structured around three tasks, namely Scanned Receipt Text Localization (Task 1), Scanned Receipt OCR (Task 2) and Key Information Extraction from Scanned Receipts (Task 3). The competition opened on 10th February, 2019 and closed on 5th May, 2019. We received 29, 24 and 18 valid submissions received for the three competition tasks, respectively. This report presents the competition datasets, define the tasks and the evaluation protocols, offer detailed submission statistics, as well as an analysis of the submitted performance. While the tasks of text localization and recognition seem to be relatively easy to tackle, it is interesting to observe the variety of ideas and approaches proposed for the information extraction task. According to the submissions' performance we believe there is still margin for improving information extraction performance, although the current dataset would have to grow substantially in following editions. Given the success of the SROIE competition evidenced by the wide interest generated and the healthy number of submissions from academic, research institutes and industry over different countries, we consider that the SROIE competition can evolve into a useful resource for the community, drawing further attention and promoting research and development efforts in this field.
Kai Chen 0006, Jianhua He 0001, Xiang Bai, Dimosthenis Karatzas, Shijian Lu, C. V. Jawahar
ICDAR5
2019 ICDAR2019 Robust Reading Challenge on Multi-lingual Scene Text Detection and Recognition - RRC-MLT-2019
abstract
With the growing cosmopolitan culture of modern cities, the need of robust Multi-Lingual scene Text (MLT) detection and recognition systems has never been more immense. With the goal to systematically benchmark and push the state-of-the-art forward, the proposed competition builds on top of the RRC-MLT-2017 with an additional end-to-end task, an additional language in the real images dataset, a large scale multi-lingual synthetic dataset to assist the training, and a baseline End-to-End recognition method. The real dataset consists of 20,000 images containing text from 10 languages. The challenge has 4 tasks covering various aspects of multi-lingual scene text: (a) text detection, (b) cropped word script classification, (c) joint text detection and script classification and (d) end-to-end detection and recognition. In total, the competition received 60 submissions from the research and industrial communities. This paper presents the dataset, the tasks and the findings of the presented RRC-MLT-2019 challenge.
Nibal Nayef, Cheng-Lin Liu 0001, Jean-Marc Ogier, Michal Busta, Pinaki Nath Chowdhury, Dimosthenis Karatzas, Wafa Khlif, Jiri Matas, Umapada Pal 0001, Jean-Christophe Burie
ICDAR7
2019 ICDAR 2019 Competition on Large-Scale Street View Text with Partial Labeling - RRC-LSVT
abstract
Robust text reading from street view images provides valuable information for various applications. Performance improvement of existing methods in such a challenging scenario heavily relies on the amount of fully annotated training data, which is costly and in-efficient to obtain. To scale up the amount of training data while keeping the labeling procedure cost-effective, this competition introduces a new challenge on Large-scale Street View Text with Partial Labeling (LSVT), providing 5,0000 and 400,000 images in full and weak annotations, respectively. This competition aims to explore the abilities of state-of-the-art methods to detect and recognize text instances from large-scale street view images, closing gaps between research benchmarks and real applications. During the competition period, a total number of 41 teams participate in the two tasks with 132 valid submissions, i.e., text detection and end-to-end text spotting. This paper includes dataset descriptions, task definitions, evaluation protocols and results summaries of ICDAR 2019-LSVT challenge.
Yipeng Sun, Dimosthenis Karatzas, Chee Seng Chan, Zihan Ni, Chee Kheng Chng, Canjie Luo, Chun Chet Ng, Junyu Han, Errui Ding, Jingtuo Liu
ICDAR2
2019 ICDAR 2019 Robust Reading Challenge on Reading Chinese Text on Signboard
abstract
Chinese scene text reading is one of the most challenging problems in computer vision and has attracted great interest. Different from English text, Chinese has more than 6000 commonly used characters and Chinese characters can be arranged in various layouts with numerous fonts. The Chinese signboards in street view are a good choice for Chinese scene text images since they have different backgrounds, fonts and layouts. We organized a competition called ICDAR2019-ReCTS, which mainly focuses on reading Chinese text on signboard. This report presents the final results of the competition. A large-scale dataset of 25,000 annotated signboard images, in which all the text lines and characters are annotated with locations and transcriptions, were released. Four tasks, namely character recognition, text line recognition, text line detection and end-to-end recognition were set up. Besides, considering the Chinese text ambiguity issue, we proposed a multi ground truth (multi-GT) evaluation method to make evaluation fairer. The competition started on March 1, 2019 and ended on April 30, 2019. 262 submissions from 46 teams are received. Most of the participants come from universities, research institutes, and tech companies in China. There are also some participants from the United States, Australia, Singapore, and Korea. 21 teams submit results for Task 1, 23 teams submit results for Task 2, 24 teams submit results for Task 3, and 13 teams submit results for Task 4. The official website for the competition is http://rrc.cvc.uab.es/?ch=12.
Rui Zhang 0056, Xiang Bai, Baoguang Shi, Dimosthenis Karatzas, Shijian Lu, C. V. Jawahar, Yongsheng Zhou, Qianyi Jiang, Nan Li 0071, Dong Wang 0004, Minghui Liao
ICDAR5
2019 Self-Supervised Visual Representations for Cross-Modal Retrieval
abstract
Cross-modal retrieval methods have been significantly improved in last years with the use of deep neural networks and large-scale annotated datasets such as ImageNet and Places. However, collecting and annotating such datasets requires a tremendous amount of human effort and, besides, their annotations are limited to discrete sets of popular visual classes that may not be representative of the richer semantics found on large-scale cross-modal retrieval datasets. In this paper, we present a self-supervised cross-modal retrieval framework that leverages as training data the correlations between images and text on the entire set of Wikipedia articles. Our method consists in training a CNN to predict: (1) the semantic context of the article in which an image is more probable to appear as an illustration, and (2) the semantic context of its caption. Our experiments demonstrate that the proposed method is not only capable of learning discriminative visual representations for solving vision tasks like classification, but that the learned representations are better for cross-modal retrieval when compared to supervised pre-training of the network on the ImageNet dataset.
Lluís Gómez i Bigorda, Marçal Rusiñol, Dimosthenis Karatzas, C. V. Jawahar
ICMR4
2019 FAST: Facilitated and Accurate Scene Text Proposals through FCN Guided Pruning
Dena Bazazian, Raul Gomez, Anguelos Nicolaou, Lluís Gómez i Bigorda, Dimosthenis Karatzas, Andrew D. Bagdanov
Pattern Recognit. Lett.5
2018 Cutting Sayre's Knot: Reading Scene Text without Segmentation. Application to Utility Meters
abstract
In this paper we present a segmentation-free system for reading text in natural scenes. A CNN architecture is trained in an end-to-end manner, and is able to directly output readings without any explicit text localization step. In order to validate our proposal, we focus on the specific case of reading utility meters. We present our results in a large dataset of images acquired by different users and devices, so text appears in any location, with different sizes, fonts and lengths, and the images present several distortions such as dirt, illumination highlights or blur.
Lluís Gómez i Bigorda, Marçal Rusiñol, Dimosthenis Karatzas
DAS3
2018 The Robust Reading Competition Annotation and Evaluation Platform
abstract
The ICDAR Robust Reading Competition (RRC), initiated in 2003 and re-established in 2011, has become a de-facto evaluation standard for robust reading systems and algorithms. Concurrent with its second incarnation in 2011, a continuous effort started to develop an on-line framework to facilitate the hosting and management of competitions. This paper outlines the Robust Reading Competition Annotation and Evaluation Platform, the backbone of the competitions. The RRC Annotation and Evaluation Platform is a modular framework, fully accessible through on-line interfaces. It comprises a collection of tools and services for managing all processes involved with defining and evaluating a research task, from dataset definition to annotation management, evaluation specification and results analysis. Although the framework has been designed with robust reading research in mind, many of the provided tools are generic by design. All aspects of the RRC Annotation and Evaluation Framework are available for research use.
Dimosthenis Karatzas, Lluís Gómez i Bigorda, Anguelos Nicolaou, Marçal Rusiñol
DAS1
2018 Single Shot Scene Text Retrieval
Lluís Gómez i Bigorda, Andrés Mafla, Marçal Rusiñol, Dimosthenis Karatzas
ECCV (14)4
2017 Self-Supervised Learning of Visual Features through Embedding Images into Text Topic Spaces
abstract
End-to-end training from scratch of current deep architectures for new computer vision problems would require Imagenet-scale datasets, and this is not always possible. In this paper we present a method that is able to take advantage of freely available multi-modal content to train computer vision algorithms without human supervision. We put forward the idea of performing self-supervised learning of visual features by mining a large scale corpus of multi-modal (text and image) documents. We show that discriminative visual features can be learnt efficiently by training a CNN to predict the semantic context in which a particular image is more probable to appear as an illustration. For this we leverage the hidden semantic structures discovered in the text corpus with a well-known topic modeling technique. Our experiments demonstrate state of the art performance in image classification, object detection, and multi-modal retrieval compared to recent self-supervised or natural-supervised approaches.
Lluís Gómez i Bigorda, Marçal Rusiñol, Dimosthenis Karatzas, C. V. Jawahar
CVPR4
2017 LSDE: Levenshtein Space Deep Embedding for Query-by-String Word Spotting
abstract
In this paper we present the LSDE string representation and its application to handwritten word spotting. LSDE is a novel embedding approach for representing strings that learns a space in which distances between projected points are correlated with the Levenshtein edit distance between the original strings. We show how such a representation produces a more semantically interpretable retrieval from the user's perspective than other state of the art ones such as PHOC and DCToW. We also conduct a preliminary handwritten word spotting experiment on the George Washington dataset.
Lluís Gómez i Bigorda, Marçal Rusiñol, Dimosthenis Karatzas
ICDAR3
2017 ICDAR2017 Robust Reading Challenge on COCO-Text
abstract
This report presents the final results of the ICDAR 2017 Robust Reading Challenge on COCO-Text. A challenge on scene text detection and recognition based on the largest real scene text dataset currently available: the COCO-Text dataset. The competition is structured around three tasks: Text Localization, Cropped Word Recognition and End-To-End Recognition. The competition received a total of 27 submissions over the different opened tasks. This report describes the datasets and the ground truth, details the performance evaluation protocols used and presents the final results along with a brief summary of the participating methods.
Raul Gomez, Baoguang Shi, Lluís Gómez i Bigorda, Lukás Neumann, Andreas Veit, Jiri Matas, Serge J. Belongie, Dimosthenis Karatzas
ICDAR8
2017 ICDAR2017 Robust Reading Challenge on Omnidirectional Video
abstract
Results of ICDAR 2017 Robust Reading Challenge on Omnidirectional Video are presented. This competition uses Downtown Osaka Scene Text (DOST) Dataset that was captured in Osaka, Japan with an omnidirectional camera. Hence, it consists of sequential images (videos) of different view angles. Regarding the sequential images as videos (video mode), two tasks of localisation and end-to-end recognition are prepared. Regarding them as a set of still images (still image mode), three tasks of localisation, cropped word recognition and end-to-end recognition are prepared. As the dataset has been captured in Japan, the dataset contains Japanese text but also include text consisting of alphanumeric characters (Latin text). Hence, a submitted result for each task is evaluated in three ways: using Japanese only ground truth (GT), using Latin only GT and using combined GTs of both. Finally, by the submission deadline, we have received two submissions in the text localisation task of the still image mode. We intend to continue the competition in the open mode. Expecting further submissions, in this report we provide baseline results in all the tasks in addition to the submissions from the community.
Masakazu Iwamura, Naoyuki Morimoto, Keishi Tainaka, Dena Bazazian, Lluís Gómez i Bigorda, Dimosthenis Karatzas
ICDAR6
2017 ICDAR2017 Robust Reading Challenge on Multi-Lingual Scene Text Detection and Script Identification - RRC-MLT
abstract
Text detection and recognition in a natural environment are key components of many applications, ranging from business card digitization to shop indexation in a street. This competition aims at assessing the ability of state-of-the-art methods to detect Multi-Lingual Text (MLT) in scene images, such as in contents gathered from the Internet media and in modern cities where multiple cultures live and communicate together. This competition is an extension of the Robust Reading Competition (RRC) which has been held since 2003 both in ICDAR and in an online context. The proposed competition is presented as a new challenge of the RRC. The dataset built for this challenge largely extends the previous RRC editions in many aspects: the multi-lingual text, the size of the dataset, the multi-oriented text, the wide variety of scenes. The dataset is comprised of 18,000 images which contain text belonging to 9 languages. The challenge is comprised of three tasks related to text detection and script classification. We have received a total of 16 participations from the research and industrial communities. This paper presents the dataset, the tasks and the findings of this RRC-MLT challenge.
Nibal Nayef, Imen Bizid, Hyunsoo Choi, Dimosthenis Karatzas, Zhenbo Luo, Umapada Pal 0001, Christophe Rigaud, Joseph Chazalon, Wafa Khlif, Muhammad Muzzamil Luqman, Jean-Christophe Burie, Cheng-Lin Liu 0001, Jean-Marc Ogier
ICDAR6
2017 ICDAR2017 Robust Reading Challenge on Text Extraction from Biomedical Literature Figures (DeTEXT)
abstract
Hundreds of millions of figures are available in the biomedical literature, representing important biomedical experimental evidence. Since text is a rich source of information in figures, automatically extracting such text may assist in the task of mining figure information and understanding biomedical documents. Unlike images in the open domain, biomedical figures present a variety of unique challenges. For example, biomedical figures typically have complex layouts, small font sizes, short text, specific text, complex symbols and irregular text arrangements. This paper presents the final results of the ICDAR 2017 Competition on Text Extraction from Biomedical Literature Figures (ICDAR2017 DeTEXT Competition), which aims at extracting (detecting and recognizing) text from biomedical literature figures. Similar to text extraction from scene images and web pictures, ICDAR2017 DeTEXT Competition includes three major tasks, i.e., text detection, cropped word recognition and end-to-end text recognition. Here, we describe in detail the data set, tasks, evaluation protocols and participants of this competition, and report the performance of the participating methods.
Xu-Cheng Yin, Dimosthenis Karatzas
ICDAR4
2017 Improving patch-based scene text script identification with ensembles of conjoined networks
Lluís Gómez i Bigorda, Anguelos Nicolaou, Dimosthenis Karatzas
Pattern Recognit.3
2017 TextProposals: A text-specific selective search algorithm for word spotting in the wild
Lluís Gómez i Bigorda, Dimosthenis Karatzas
Pattern Recognit.2
2016 A Fine-Grained Approach to Scene Text Script Identification
abstract
This paper focuses on the problem of script identification in unconstrained scenarios. Script identification is an important prerequisite to recognition, and an indispensable condition for automatic text understanding systems designed for multi-language environments. Although widely studied for document images and handwritten documents, it remains an almost unexplored territory for scene text images. We detail a novel method for script identification in natural images that combines convolutional features and the Naive-Bayes Nearest Neighbor classifier. The proposed framework efficiently exploits the discriminative power of small stroke-parts, in a fine-grained classification framework. In addition, we propose a new public benchmark dataset for the evaluation of joint text detection and script identification in natural scenes. Experiments done in this new dataset demonstrate that the proposed method yields state of the art results, while it generalizes well to different datasets and variable number of scripts. The evidence provided shows that multi-lingual scene text recognition in the wild is a viable proposition. Source code of the proposed method is made available online.
Lluís Gómez i Bigorda, Dimosthenis Karatzas
DAS2
2016 Human-Document Interaction Systems - A New Frontier for Document Image Analysis
abstract
All indications show that paper documents will not cede in favour of their digital counterparts, but will instead be used increasingly in conjunction with digital information. An open challenge is how to seamlessly link the physical with the digital -- how to continue taking advantage of the important affordances of paper, without missing out on digital functionality. This paper presents the authors' experience with developing systems for Human-Document Interaction based on augmented document interfaces and examines new challenges and opportunities arising for the document image analysis field in this area. The system presented combines state of the art camera-based document image analysis techniques with a range of complementary technologies to offer fluid Human-Document Interaction. Both fixed and nomadic setups are discussed that have gone through user testing in real-life environments, and use cases are presented that span the spectrum from business to educational applications.
Dimosthenis Karatzas, Vincent Poulain D'Andecy, Marçal Rusiñol, Antoni Chica, Pere-Pau Vázquez
DAS1
2016 Visual Script and Language Identification
abstract
In this paper we introduce a script identification method based on hand-crafted texture features and an artificial neural network. The proposed pipeline achieves near state-of-the-art performance for script identification of video-text and state-of-the-art performance on visual language identification of handwritten text. More than using the deep network as a classifier, the use of its intermediary activations as a learned metric demonstrates remarkable results and allows the use of discriminative models on unknown classes. Comparative experiments in video-text and text in the wild datasets provide insights on the internals of the proposed deep network.
Anguelos Nicolaou, Andrew D. Bagdanov, Lluís Gómez i Bigorda, Dimosthenis Karatzas
DAS4
2016 A fast hierarchical method for multi-script and arbitrary oriented scene text extraction
Lluís Gómez i Bigorda, Dimosthenis Karatzas
Int. J. Document Anal. Recognit.2
2015 Object proposals for text extraction in the wild
abstract
Object Proposals is a recent computer vision technique receiving increasing interest from the research community. Its main objective is to generate a relatively small set of bounding box proposals that are most likely to contain objects of interest. The use of Object Proposals techniques in the scene text understanding field is innovative. Motivated by the success of powerful while expensive techniques to recognize words in a holistic way, Object Proposals techniques emerge as an alternative to the traditional text detectors. In this paper we study to what extent the existing generic Object Proposals methods may be useful for scene text understanding. Also, we propose a new Object Proposals algorithm that is specifically designed for text and compare it with other generic methods in the state of the art. Experiments show that our proposal is superior in its ability of producing good quality word proposals in an efficient way. The source code of our method is made publicly available1.
Lluís Gómez i Bigorda, Dimosthenis Karatzas
ICDAR2
2015 Novel line verification for multiple instance focused retrieval in document collections
abstract
Spatial verification is typically employed to check the spatial consistency among matched local features and to remove outliers. However, when looking for multiple instances of the query within a target image, RANSAC algorithms which are widely applied in many one-to-one matching applications might fail due to the large proportion of “outliers” - correct matches corresponding to other instances. On the other hand, geometrical verification methods are more robust to outliers but usually suffer from high computational costs. In this paper, we introduce a novel two-step line verification method which is more flexible than existing methods and leads to lower computational complexity especially when multiple instances of a query are sought. We study this approach within an information extraction scenario, where the objective is to locate document structures indicative of certain type of information (e.g. different records on invoices).
Hongxing Gao, Marçal Rusiñol, Dimosthenis Karatzas, Josep Lladós 0001, Rajiv Jain, David S. Doermann
ICDAR3
2015 Efficient indexing for Query By String text retrieval
abstract
This paper deals with Query By String word spotting in scene images. A hierarchical text segmentation algorithm based on text specific selective search is used to find text regions. These regions are indexed per character n-grams present in the text region. An attribute representation based on Pyramidal Histogram of Characters (PHOC) is used to compare text regions with the query text. For generation of the index a similar attribute space based Pyramidal Histogram of character n-grams is used. These attribute models are learned using linear SVMs over the Fisher Vector [1] representation of the images along with the PHOC labels of the corresponding strings.
Suman K. Ghosh, Lluís Gómez i Bigorda, Dimosthenis Karatzas, Ernest Valveny
ICDAR3
2015 ICDAR 2015 competition on Robust Reading
abstract
Results of the ICDAR 2015 Robust Reading Competition are presented. A new Challenge 4 on Incidental Scene Text has been added to the Challenges on Born-Digital Images, Focused Scene Images and Video Text. Challenge 4 is run on a newly acquired dataset of 1,670 images evaluating Text Localisation, Word Recognition and End-to-End pipelines. In addition, the dataset for Challenge 3 on Video Text has been substantially updated with more video sequences and more accurate ground truth data. Finally, tasks assessing End-to-End system performance have been introduced to all Challenges. The competition took place in the first quarter of 2015, and received a total of 44 submissions. Only the tasks newly introduced in 2015 are reported on. The datasets, the ground truth specification and the evaluation protocols are presented together with the results and a brief summary of the participating methods.
Dimosthenis Karatzas, Lluís Gómez i Bigorda, Anguelos Nicolaou, Suman K. Ghosh, Andrew D. Bagdanov, Masakazu Iwamura, Jiri Matas, Lukás Neumann, Vijay Chandrasekhar 0001, Shijian Lu, Faisal Shafait, Seiichi Uchida, Ernest Valveny
ICDAR1
2015 Sparse radial sampling LBP for writer identification
abstract
Sampling Local Binary Patterns, a variant of Local Binary Patterns (LBP) for text-as-texture classification. By adapting and extending the standard LBP operator to the particularities of text we get a generic text-as-texture classification scheme and apply it to writer identification. In experiments on CVL and ICDAR 2013 datasets, the proposed feature-set and a simple end-to-end pipeline demonstrate State-Of-the-Art (SOA) performance. Among the SOA, the proposed method is the only one that is based on dense extraction of a single local feature descriptor. This makes it fast and applicable at the earliest stages in a DIA pipeline without the need for segmentation, binarization, or extraction of multiple features.
Anguelos Nicolaou, Andrew D. Bagdanov, Marcus Liwicki, Dimosthenis Karatzas
ICDAR4
2015 Knowledge-driven understanding of images in comic books
Christophe Rigaud, Clément Guérin, Dimosthenis Karatzas, Jean-Christophe Burie, Jean-Marc Ogier
Int. J. Document Anal. Recognit.3
2015 Preface
Faisal Shafait, Dimosthenis Karatzas, Seiichi Uchida, Masakazu Iwamura
Int. J. Document Anal. Recognit.2
2014 A Cache Language Model for Whole Document Handwriting Recognition
abstract
With increasing computational power, the trend in unconstrained text recognition is going towards whole document processing. For this task, more sophisticated language models can be employed. One approach is to take advantage the fact that the text of a document normally deals with a specific topic and hence the word occurrence probability is biased. Cache language models combine information about recent words, the cache, with a general statistical language model to increase the recognition rate. In this work we introduce a modified version of the cache language model to the task of handwriting recognition, where the N-best recognition output of the entire document is used to refine the language model for a consecutive recognition pass. An experimental evaluation on the IAM database demonstrates that the word error rate can be reduced with the proposed cache language model.
Volkmar Frinken, Dimosthenis Karatzas, Andreas Fischer 0002
Document Analysis Systems2
2014 An On-line Platform for Ground Truthing and Performance Evaluation of Text Extraction Systems
abstract
This work presents a set of on-line software tools for creating ground truth and calculating performance evaluation metrics for text extraction tasks such as localization, segmentation and recognition. The platform supports the definition of comprehensive ground truth information at different text representation levels while it offers centralised management and quality control of the ground truthing effort. It implements a range of state of the art performance evaluation algorithms and offers functionality for the definition of evaluation scenarios, on-line calculation of various performance metrics and visualisation of the results. The presented platform, which comprises the backbone of the ICDAR 2011 (challenge 1) and 2013 (challenges 1 and 2) Robust Reading competitions, is now made available for public use.
Dimosthenis Karatzas, Sergi Robles, Lluís Gómez i Bigorda
Document Analysis Systems1
2014 Color Descriptor for Content-Based Drawing Retrieval
abstract
Human detection in computer vision field is an active field of research. Extending this to human-like drawings such as the main characters in comic book stories is not trivial. Comics analysis is a very recent field of research at the intersection of graphics, texts, objects and people recognition. The detection of the main comic characters is an essential step towards a fully automatic comic book understanding. This paper presents a color-based approach for comics character retrieval using content-based drawing retrieval and color palette.
Christophe Rigaud, Dimosthenis Karatzas, Jean-Christophe Burie, Jean-Marc Ogier
Document Analysis Systems2
2014 Embedding Document Structure to Bag-of-Words through Pair-wise Stable Key-Regions
abstract
Since the document structure carries valuable discriminative information, plenty of efforts have been made for extracting and understanding document structure among which layout analysis approaches are the most commonly used. In this paper, Distance Transform based MSER (DTMSER) is employed to efficiently extract the document structure as a dendrogram of key-regions which roughly correspond to structural elements such as characters, words and paragraphs. Inspired by the Bag of Words (BoW) framework, we propose an efficient method for structural document matching by representing the document image as a histogram of key-region pairs encoding structural relationships. Applied to the scenario of document image retrieval, experimental results demonstrate a remarkable improvement when comparing the proposed method with typical BoW and pyramidal BoW methods.
Hongxing Gao, Marçal Rusiñol, Dimosthenis Karatzas, Josep Lladós 0001
ICPR3
2014 MSER-Based Real-Time Text Detection and Tracking
abstract
We present a hybrid algorithm for detection and tracking of text in natural scenes that goes beyond the full-detection approaches in terms of time performance optimization. A state-of-the-art scene text detection module based on Maximally Stable Extremal Regions (MSER) is used to detect text asynchronously, while on a separate thread detected text objects are tracked by MSER propagation. The cooperation of these two modules yields real time video processing at high frame rates even on low-resource devices.
Lluís Gómez i Bigorda, Dimosthenis Karatzas
ICPR2
2014 Multimodal page classification in administrative document image streams
Marçal Rusiñol, Volkmar Frinken, Dimosthenis Karatzas, Andrew D. Bagdanov, Josep Lladós 0001
Int. J. Document Anal. Recognit.3
2013 Key-Region Detection for Document Images - Application to Administrative Document Retrieval
abstract
In this paper we argue that a key-region detector designed to take into account the special characteristics of document images can result in the detection of less and more meaningful key-regions. We propose a fast key-region detector able to capture aspects of the structural information of the document, and demonstrate its efficiency by comparing against standard detectors in an administrative document retrieval scenario. We show that using the proposed detector results to a smaller number of detected key-regions and higher performance without any drop in speed compared to standard state of the art detectors.
Hongxing Gao, Marçal Rusiñol, Dimosthenis Karatzas, Josep Lladós 0001, Tomokazu Sato, Masakazu Iwamura, Koichi Kise
ICDAR3
2013 Multi-script Text Extraction from Natural Scenes
abstract
Scene text extraction methodologies are usually based in classification of individual regions or patches, using a priori knowledge for a given script or language. Human perception of text, on the other hand, is based on perceptual organisation through which text emerges as a perceptually significant group of atomic objects. Therefore humans are able to detect text even in languages and scripts never seen before. In this paper, we argue that the text extraction problem could be posed as the detection of meaningful groups of regions. We present a method built around a perceptual organisation framework that exploits collaboration of proximity and similarity laws to create text-group hypotheses. Experiments demonstrate that our algorithm is competitive with state of the art approaches on a standard dataset covering text in variable orientations and two languages.
Lluís Gómez i Bigorda, Dimosthenis Karatzas
ICDAR2
2013 Document Classification and Page Stream Segmentation for Digital Mailroom Applications
abstract
In this paper we present a method for the segmentation of continuous page streams into multipage documents and the simultaneous classification of the resulting documents. We first present an approach to combine the multiple pages of a document into a single feature vector that represents the whole document. Despite its simplicity and low computational cost, the proposed representation yields results comparable to more complex methods in multipage document classification tasks. We then exploit this representation in the context of page stream segmentation. The most plausible segmentation of a page stream into a sequence of multipage documents is obtained by optimizing a statistical model that represents the probability of each segmented multipage document belonging to a particular class. Experimental results are reported on a large sample of real administrative multipage documents.
Albert Gordo, Marçal Rusiñol, Dimosthenis Karatzas, Andrew D. Bagdanov
ICDAR3
2013 ICDAR 2013 Robust Reading Competition
abstract
This report presents the final results of the ICDAR 2013 Robust Reading Competition. The competition is structured in three Challenges addressing text extraction in different application domains, namely born-digital images, real scene images and real-scene videos. The Challenges are organised around specific tasks covering text localisation, text segmentation and word recognition. The competition took place in the first quarter of 2013, and received a total of 42 submissions over the different tasks offered. This report describes the datasets and ground truth specification, details the performance evaluation protocols used and presents the final results along with a brief summary of the participating methods.
Dimosthenis Karatzas, Faisal Shafait, Seiichi Uchida, Masakazu Iwamura, Lluís Gómez i Bigorda, Sergi Robles, Joan Mas Romeu, David Fernández Mota, Jon Almazán, Lluís-Pere de las Heras
ICDAR1
2013 An Active Contour Model for Speech Balloon Detection in Comics
abstract
Comic books constitute an important cultural heritage asset in many countries. Digitization combined with subsequent comic book understanding would enable a variety of new applications, including content-based retrieval and content retargeting. Document understanding in this domain is challenging as comics are semi-structured documents, combining semantically important graphical and textual parts. Few studies have been done in this direction. In this work we detail a novel approach for closed and non-closed speech balloon localization in scanned comic book pages, an essential step towards a fully automatic comic book understanding. The approach is compared with existing methods for closed balloon localization found in the literature and results are presented.
Christophe Rigaud, Jean-Christophe Burie, Jean-Marc Ogier, Dimosthenis Karatzas, Joost van de Weijer 0001
ICDAR4
2013 Towards multispectral data acquisition with hand-held devices
abstract
We propose a method to acquire multispectral data with handheld devices with front-mounted RGB cameras. We propose to use the display of the device as an illuminant while the camera captures images illuminated by the red, green and blue primaries of the display. Three illuminants and three response functions of the camera lead to nine response values which are used for reflectance estimation. Results are promising and show that the accuracy of the spectral reconstruction improves in the range of 30-40% over the spectral reconstruction based on a single illuminant. Furthermore, we propose to compute sensor-illuminant aware linear basis by discarding the part of the reflectances that falls in the sensor-illuminant null-space. We show experimentally that optimizing reflectance estimation on these new basis functions decreases the RMSE significantly over basis functions that are independent to sensor-illuminant. We conclude that, multispectral data acquisition is potentially possible with consumer hand-held devices such as tablets, mobiles, and laptops, opening up applications which are currently considered to be unrealistic.
Rahat Khan, Joost van de Weijer 0001, Dimosthenis Karatzas, Damien Muselet
ICIP3
2012 Multipage document retrieval by textual and visual representations
Marçal Rusiñol, Dimosthenis Karatzas, Andrew D. Bagdanov, Josep Lladós 0001
ICPR2
2011 Interactive Trademark Image Retrieval by Fusing Semantic and Visual Content
Marçal Rusiñol, David Aldavert, Dimosthenis Karatzas, Ricardo Toledo, Josep Lladós 0001
ECIR3
2011 ICDAR 2011 Robust Reading Competition - Challenge 1: Reading Text in Born-Digital Images (Web and Email)
abstract
This paper presents the results of the first Challenge of ICDAR 2011 Robust Reading Competition. Challenge 1 is focused on the extraction of text from born-digital images, specifically from images found in Web pages and emails. The challenge was organized in terms of three tasks that look at different stages of the process: text localization, text segmentation and word recognition. In this paper we present the results of the challenge for all three tasks, and make an open call for continuous participation outside the context of ICDAR 2011.
Dimosthenis Karatzas, Sergi Robles, Joan Mas Romeu, Farshad Nourbakhsh, Partha Pratim Roy 0001
ICDAR1
2011 A generic framework for median graph computation based on a recursive embedding approach
Miquel Ferrer, Dimosthenis Karatzas, Ernest Valveny, Itziar Bardají, Horst Bunke
Comput. Vis. Image Underst.2
2011 Report from the AND 2009 working group on noisy text datasets
Simone Marinai, Dimosthenis Karatzas
Int. J. Document Anal. Recognit.2
2010 A framework for the assessment of text extraction algorithms on complex colour images
abstract
The availability of open, ground-truthed datasets and clear performance metrics is a crucial factor in the development of an application domain. The domain of colour text image analysis (real scenes, Web and spam images, scanned colour documents) has traditionally suffered from a lack of a comprehensive performance evaluation framework. Such a framework is extremely difficult to specify, and corresponding pixel-level accurate information tedious to define. In this paper we discuss the challenges and technical issues associated with developing such a framework. Then, we describe a complete framework for the evaluation of text extraction methods at multiple levels, provide a detailed ground-truth specification and present a case study on how this framework can be used in a real-life situation.
Antonio Clavelli, Dimosthenis Karatzas, Josep Lladós 0001
Document Analysis Systems2
2010 A polar-based logo representation based on topological and colour features
abstract
In this paper, we propose a novel rotation and scale invariant method for colour logo retrieval and classification, which involves performing a simple colour segmentation and subsequently describing each of the resultant colour components based on a set of topological and colour features. A polar representation is used to represent the logo and the subsequent logo matching is based on Cyclic Dynamic Time Warping (CDTW). We also show how combining information about the global distribution of the logo components and their local neighbourhood using the Delaunay triangulation allows to improve the results. All experiments are performed on a dataset of 2500 instances of 100 colour logo images in different rotations and scales.
Farshad Nourbakhsh, Dimosthenis Karatzas, Ernest Valveny
Document Analysis Systems2
2010 Perceptual Image Retrieval by Adding Color Information to the Shape Context Descriptor
abstract
In this paper we present a method for the retrieval of images in terms of perceptual similarity. Local color information is added to the shape context descriptor in order to obtain an object description integrating both shape and color as visual cues. We use a color naming algorithm in order to represent the color information from a perceptual point of view. The proposed method has been tested in two different applications, an object retrieval scenario based on color sketch queries and a color trademark retrieval problem. Experimental results show that the addition of the color information significantly outperforms the sole use of the shape context descriptor.
Marçal Rusiñol, Farshad Nourbakhsh, Dimosthenis Karatzas, Ernest Valveny, Josep Lladós 0001
ICPR3
2010 Generation of synthetic documents for performance evaluation of symbol recognition & spotting systems
Mathieu Delalandre, Ernest Valveny, Tony P. Pridmore, Dimosthenis Karatzas
Int. J. Document Anal. Recognit.4
2010 Rotation invariant hand-drawn symbol recognition based on a dynamic time warping model
Alicia Fornés, Josep Lladós 0001, Gemma Sánchez, Dimosthenis Karatzas
Int. J. Document Anal. Recognit.4
2009 Text Segmentation in Colour Posters from the Spanish Civil War Era
abstract
The extraction of textual content from colour documents of a graphical nature is a complicated task. The text can be rendered in any colour, size and orientation while the existence of complex background graphics with repetitive patterns can make its localization and segmentation extremely difficult. Here, we propose a new method for extracting textual content from such colour images that makes no assumption as to the size of the characters, their orientation or colour, while it is tolerant to characters that do not follow a straight baseline. We evaluate this method on a collection of documents with historical connotations: the posters from the Spanish Civil War.
Antonio Clavelli, Dimosthenis Karatzas
ICDAR2
2008 Detecting Gradients in Text Images Using the Hough Transform
abstract
The use of gradients in text images is nowadays quite frequent. Existing segmentation methods encounter serious problems when it comes to modern text images where gradients might appear in the background or the foreground or both at the same time. This paper presents an approach for lightness gradient areas detection based on the Hough Transform. The issues arising are discussed, and results are presented on a dataset comprising Web images, logos and scanned documents.
Dimosthenis Karatzas
Document Analysis Systems1
2008 HistoSketch: A Semi-Automatic Annotation Tool for Archival Documents
abstract
This article describes a sketch-based framework for semi-automatic annotation of historical document collections. It is motivated by the fact that fully automatic methods, while helpful for extracting metadata from large collections, have two main drawbacks in a real-world application: (i) they are error-prone and (ii) they only capture a subset of all the knowledge in the document base, both meaning that manual intervention is always required. Therefore, we have developed a practical framework for allowing experts to extract knowledge from document collections in a sketch-based scenario. The main possibilities of the proposed framework are: (a) browsing the collection efficiently, (b) providing gestures for metadata input, (c) supporting handwritten notes and (d) providing gestures for launching automatic extraction processes such as OCR or word spotting.
Joan Mas Romeu, José A. Rodríguez 0001, Dimosthenis Karatzas, Gemma Sánchez, Josep Lladós 0001
Document Analysis Systems3
2008 Segmentation robust to the vignette effect for machine vision systems
abstract
The vignette effect (radial fall-off) is commonly encountered in images obtained through certain image acquisition setups and can seriously hinder automatic analysis processes. In this paper we present a fast and efficient method for dealing with vignetting in the context of object segmentation in an existing industrial inspection setup. The vignette effect is modelled here as a circular, non-linear gradient. The method estimates the gradient parameters and employs them to perform segmentation. Segmentation results on a variety of images indicate that the presented method is able to successfully tackle the vignette effect.
Dimosthenis Karatzas, Marçal Rusiñol, Jacobus Antens, Miquel Ferrer
ICPR1
2007 Colour text segmentation in web images based on human perception
Dimosthenis Karatzas, Apostolos Antonacopoulos
Image Vis. Comput.1
2006 Ground Truth for Layout Analysis Performance Evaluation
Apostolos Antonacopoulos, Dimosthenis Karatzas, David Bridson
Document Analysis Systems2
2005 Semantics-Based Content Extraction in Typewritten Historical Documents
abstract
This paper presents a flexible approach to extracting content from scanned historical documents using semantic information. The final electronic document is the result of a "digital historical document lifecycle" process, where the expert knowledge of the historian/archivist user is incorporated at different stages. Results show that such a conversion strategy aided by (expert) user-specified semantic information and which enables the processing of individual parts of the document in a specialised way, produces superior (in a variety of significant ways) results than document analysis and understanding techniques devised for contemporary documents.
Apostolos Antonacopoulos, Dimosthenis Karatzas
ICDAR2
2004 A Complete Approach to the Conversion of Typewritten Historical Documents for Digital Archives
Apostolos Antonacopoulos, Dimosthenis Karatzas
Document Analysis Systems2
2004 The lifecycle of a digital historical document: structure and content
abstract
This paper describes the lifecycle of a digital historical document, from template-based structure definition through to content extraction from the scanned pages and its final reconstitution as an electronic document (combining content and semantic information) along with the tools that have been created to realise each stage in the lifecycle. The whole approach is described in the context of different types of typewritten documents relating to prisoners in World-War II concentration camps and is the result of a multinational collaboration under the MEMORIAL project funded (€1.5M) by the European Union (www.memorial-project.info). Extensive tests with historians/archivists and evaluation of the content extraction results indicate the superior performance of the whole semantics-driven approach both over manual transcription and over the semi-automated application of off-the-shelf OCR and the use of a conventional (text and layout) document format.
Apostolos Antonacopoulos, Dimosthenis Karatzas, Henryk Krawczyk, Bogdan Wiszniewski
ACM Symposium on Document Engineering2
2003 ICDAR 2003 Page Segmentation Competition
Apostolos Antonacopoulos, Basilios Gatos, Dimosthenis Karatzas
ICDAR3
2003 Two Approaches for Text Segmentation in Web Images
abstract
There is a significant need to recognise the text in images on Web pages, both for effective indexing and for presentation by non-visual means (e.g., audio). This paper presents and compares two novel methods for the segmentation of characters for subsequent extraction and recognition. The novelty of both approaches is the combination of (different in each case) topological features of characters with an anthropocentric perspective of colour perception - in preference to RGB space analysis. Both approaches enable the extraction of text in complex situations such as in the presence of varying colour and texture (characters and background).
Dimosthenis Karatzas, Apostolos Antonacopoulos
ICDAR1
2002 Fuzzy Segmentation of Characters in Web Images Based on Human Colour Perception
Apostolos Antonacopoulos, Dimosthenis Karatzas
Document Analysis Systems2