Querying out-of-vocabulary words in lexicon-based keyword spotting

The final publication is available at Springer via http://dx.doi.org/10.1007/s00521-016-2197-8[EN] Lexicon-based handwritten text keyword spotting (KWS) has proven to be a faster and more accurate alternative to lexicon-free methods. Nevertheless, since lexicon-based KWS relies on a predefined vocabulary, fixed in the training phase, it does not support queries involving out-of-vocabulary (OOV) keywords. In this paper, we outline previous work aimed at solving this problem and present a new approach based on smoothing the (null) scores of OOV keywords by means of the information provided by ``similar'' in-vocabulary words. Good results achieved using this approach are compared with previously published alternatives on different data sets.This work was partially supported by the Spanish MEC under FPU Grant FPU13/06281, by the Generalitat Valenciana under the Prometeo/2009/014 Project Grant ALMA-MATER, and through the EU Projects: HIMANIS (JPICH programme, Spanish grant Ref. PCIN-2015-068) and READ (Horizon-2020 programme, grant Ref. 674943).Puigcerver, J.; Toselli, AH.; Vidal, E. (2016). Querying out-of-vocabulary words in lexicon-based keyword spotting. Neural Computing and Applications. 1-10. https://doi.org/10.1007/s00521-016-2197-8S110Almazan J, Gordo A, Fornes A, Valveny E (2013) Handwritten word spotting with corrected attributes. In: 2013 IEEE international conference on computer vision (ICCV), pp 1017–1024. doi: 10.1109/ICCV.2013.130Amengual JC, Vidal E (2000) On the estimation of error-correcting parameters. In: Proceedings 15th international conference on pattern recognition, 2000, vol 2, pp 883–886Fernández D, Lladós J, Fornés A (2011) Handwritten word spotting in old manuscript images using a pseudo-structural descriptor organized in a hash structure. In: Vitri'a J, Sanches JM, Hern'andez M (eds) Pattern recognition and image analysis: Proceedings of 5th Iberian Conference, IbPRIA 2011, Las Palmas de Gran Canaria, Spain, June 8–10. Springer, Berlin, Heidelberg, pp 628–635. doi: 10.1007/978-3-642-21257-4_78Fischer A, Keller A, Frinken V, Bunke H (2012) Lexicon-free handwritten word spotting using character HMMs. Pattern Recognit Lett 33(7):934–942. doi: 10.1016/j.patrec.2011.09.009 Special Issue on Awards from ICPR 2010Fornés A, Frinken V, Fischer A, Almazán J, Jackson G, Bunke H (2011) A keyword spotting approach using blurred shape model-based descriptors. In: Proceedings of the 2011 workshop on historical document imaging and processing, pp 83–90. ACMFrinken V, Fischer A, Manmatha R, Bunke H (2012) A novel word spotting method based on recurrent neural networks. IEEE Trans Pattern Anal Mach Intell 34(2):211–224. doi: 10.1109/TPAMI.2011.113Gatos B, Pratikakis I (2009) Segmentation-free word spotting in historical printed documents. In: 10th International conference on document analysis and recognition, 2009. ICDAR’09, pp 271–275. IEEEJelinek F (1998) Statistical methods for speech recognition. MIT Press, CambridgeKneser R, Ney H (1995) Improved backing-off for N-gram language modeling. In: International conference on acoustics, speech and signal processing (ICASSP ’95), vol 1, pp 181–184. IEEE Computer Society, Los Alamitos, CA, USA. doi: http://doi.ieeecomputersociety.org/10.1109/ICASSP.1995.479394Kolcz A, Alspector J, Augusteijn M, Carlson R, Popescu GV (2000) A line-oriented approach to word spotting in handwritten documents. Pattern Anal Appl 3:153–168. doi: 10.1007/s100440070020Konidaris T, Gatos B, Ntzios K, Pratikakis I, Theodoridis S, Perantonis SJ (2007) Keyword-guided word spotting in historical printed documents using synthetic data and user feedback. Int J Doc Anal Recognit 9(2–4):167–177Kumar G, Govindaraju V (2014) Bayesian active learning for keyword spotting in handwritten documents. In: 2014 22nd International conference on pattern recognition (ICPR), pp 2041–2046. IEEELevenshtein VI (1966) Binary codes capable of correcting deletions, insertions and reversals. Sov Phys Dokl 10(8):707–710Manning CD, Raghavan P, Schtze H (2008) Introduction to information retrieval. Cambridge University Press, New YorkMarti UV, Bunke H (2002) The IAM-database: an English sentence database for offline handwriting recognition. Int J Doc Anal Recognit 5(1):39–46. doi: 10.1007/s100320200071Puigcerver J, Toselli AH, Vidal E (2014) Word-graph and character-lattice combination for KWS in handwritten documents. In: 14th International conference on frontiers in handwriting recognition (ICFHR), pp 181–186Puigcerver J, Toselli AH, Vidal E (2014) Word-graph-based handwriting keyword spotting of out-of-vocabulary queries. In: 22nd International conference on pattern recognition (ICPR), pp 2035–2040Puigcerver J, Toselli AH, Vidal E (2015) A new smoothing method for lexicon-based handwritten text keyword spotting. In: 7th Iberian conference on pattern recognition and image analysis. SpringerRath T, Manmatha R (2007) Word spotting for historical documents. Int J Doc Anal Recognit 9:139–152Robertson S. (2008) A new interpretation of average precision. In: Proceedings of the international. ACM SIGIR conference on research and development in information retrieval (SIGIR ’08), pp 689–690. ACM, New York, NY, USA. doi: http://doi.acm.org/10.1145/1390334.1390453Rodriguez-Serrano JA, Perronnin F (2009) Handwritten word-spotting using hidden markov models and universal vocabularies. Pattern Recognit 42(9):2106–2116. doi: 10.1016/j.patcog.2009.02.005 . http://www.sciencedirect.com/science/article/pii/S0031320309000673Rusinol M, Aldavert D, Toledo R, Llados J (2011) Browsing heterogeneous document collections by a segmentation-free word spotting method. In: International conference on document analysis and recognition (ICDAR), pp 63–67. doi: 10.1109/ICDAR.2011.22Shang H, Merrettal T (1996) Tries for approximate string matching. IEEE Trans Knowl Data Eng 8(4):540–547Toselli AH, Vidal E (2013) Fast HMM-Filler approach for key word spotting in handwritten documents. In: Proceedings of the 12th international conference on document analysis and recognition (ICDAR), pp 501–505Toselli AH, Vidal E (2014) Word-graph based handwriting key-word spotting: impact of word-graph size on performance. In: 11th IAPR international workshop on document analysis systems (DAS), pp 176–180. IEEEToselli AH, Vidal E, Romero V, Frinken V (2013) Word-graph based keyword spotting and indexing of handwritten document images. Technical report, Universitat Politécnica de ValénciaVidal E, Toselli AH, Puigcerver J (2015) High performance query-by-example keyword spotting using query-by-string techniques. In: 2015 13th International conference on document analysis and recognition (ICDAR), pp 741–745. IEEEWoodland P, Leggetter C, Odell J, Valtchev V, Young S (1995) The 1994 HTK large vocabulary speech recognition system. In: International conference on acoustics, speech, and signal processing (ICASSP ’95), vol 1, pp 73 –76. doi: 10.1109/ICASSP.1995.479276Wshah S, Kumar G, Govindaraju V (2012) Script independent word spotting in offline handwritten documents based on hidden markov models. In: 2012 International conference on frontiers in handwriting recognition (ICFHR), pp 14–19. doi: 10.1109/ICFHR.2012.26

HMM word graph based keyword spotting in handwritten document images

[EN] Line-level keyword spotting (KWS) is presented on the basis of frame-level word posterior probabilities. These posteriors are obtained using word graphs derived from the recogni- tion process of a full-fledged handwritten text recognizer based on hidden Markov models and N-gram language models. This approach has several advantages. First, since it uses a holistic, segmentation-free technology, it does not require any kind of word or charac- ter segmentation. Second, the use of language models allows the context of each spotted word to be taken into account, thereby considerably increasing KWS accuracy. And third, the proposed KWS scores are based on true posterior probabilities, taking into account all (or most) possible word segmentations of the input image. These scores are properly bounded and normalized. This mathematically clean formulation lends itself to smooth, threshold-based keyword queries which, in turn, permit comfortable trade-offs between search precision and recall. Experiments are carried out on several historic collections of handwritten text images, as well as a well-known data set of modern English handwrit- ten text. According to the empirical results, the proposed approach achieves KWS results comparable to those obtained with the recently-introduced "BLSTM neural networks KWS" approach and clearly outperform the popular, state-of-the-art "Filler HMM" KWS method. Overall, the results clearly support all the above-claimed advantages of the proposed ap- proach.This work has been partially supported by the Generalitat Valenciana under the Prometeo/2009/014 project grant ALMA-MATER, and through the EU projects: HIMANIS (JPICH programme, Spanish grant Ref. PCIN-2015-068) and READ (Horizon 2020 programme, grant Ref. 674943).Toselli, AH.; Vidal, E.; Romero, V.; Frinken, V. (2016). HMM word graph based keyword spotting in handwritten document images. Information Sciences. 370:497-518. https://doi.org/10.1016/j.ins.2016.07.063S49751837

Probabilistic multi-word spotting in handwritten text images

[EN] Keyword spotting techniques are becoming cost-effective solutions for information retrieval in handwritten documents. We explore the extension of the single-word, line-level probabilistic indexing approach described in our previous works to allow for page-level search of queries consisting in Boolean combinations of several single-keywords. We propose heuristic rules to combine the single-word relevance probabilities into probabilistically consistent confidence scores of the multi-word boolean combinations. An empirical study, also presented in this paper, evaluates the search performance of word-pair queries involving AND and OR Boolean operations. Results of this study support the proposed approach and clearly show its effectiveness. Finally, a web-based demonstration system based on the proposed methods is presented.This work was partially supported by the Generalitat Valenciana under the Prometeo/2009/014 Project Grant ALMAMATER, Spanish MEC under Grant FPU13/06281, and through the EU projects: HIMANIS (JPICH programme, Spanish grant Ref. PCIN-2015-068) and READ (Horizon-2020 programme, Grant Ref. 674943).Toselli, AH.; Vidal, E.; Puigcerver, J.; Noya-García, E. (2019). Probabilistic multi-word spotting in handwritten text images. Pattern Analysis and Applications. 22(1):23-32. https://doi.org/10.1007/s10044-018-0742-zS2332221Andreu Sanchez J, Romero V, Toselli A, Vidal E (2014) ICFHR2014 competition on handwritten text recognition on transcriptorium datasets (HTRtS). In: 14th International conference on frontiers in handwriting recognition (ICFHR), 2014, pp 785–790Bazzi I, Schwartz R, Makhoul J (1999) An omnifont open-vocabulary OCR system for English and Arabic. IEEE Trans Pattern Anal Mach Intell 21(6):495–504Bluche T, Hamel S, Kermorvant C, Puigcerver J, Stutzmann D, Toselli AH, Vidal E (2017) Preparatory KWS experiments for large-scale indexing of a vast medieval manuscript collection in the hIMANIS Project. In: 14th International conference on document analysis and recognition (ICDAR). (Accepted)Bluche T, Hamel S, Kermorvant C, Puigcerver J, Stutzmann D, Toselli AH, Vidal E (2017) Preparatory kws experiments for large-scale indexing of a vast medieval manuscript collection in the himanis project. In: 2017 14th IAPR international conference on document analysis and recognition (ICDAR), vol. 01, pp 311–316. https://doi.org/10.1109/ICDAR.2017.59Boole G (1854) An investigation of the laws of thought on which are founded the mathematical theories of logic and probabilities. Macmillan, New YorkCauser T, Wallace V (2012) Building a volunteer community: results and findings from Transcribe Bentham. Digital Humanities Quarterly 6España-Boquera S, Castro-Bleda MJ, Gorbe-Moya J, Zamora-Martinez F (2011) Improving offline handwritten text recognition with hybrid hmm/ann models. IEEE Trans Pattern Anal Mach Intell 33(4):767–779. https://doi.org/10.1109/TPAMI.2010.141Fischer A, Wuthrich M, Liwicki M, Frinken V, Bunke H, Viehhauser G, Stolz M (2009) Automatic transcription of handwritten medieval documents. In: 15th International conference on virtual systems and multimedia, 2009. VSMM ’09, pp 137–142. https://doi.org/10.1109/VSMM.2009.26Fréchet M (1935) Généralisations du théorème des probabilités totales. Seminarjum MatematyczneFréchet M (1951) Sur les tableaux de corrélation dont les marges sont données. Ann Univ Lyon 3 $$^{\wedge }$$ ∧ e ser Sci Sect A 14:53–77Graves A, Liwicki M, Fernández S, Bertolami R, Bunke H, Schmidhuber J (2009) A novel connectionist system for unconstrained handwriting recognition. IEEE Trans Pattern Anal Mach Intell 31(5):855–868Jelinek F (1998) Statistical methods for speech recognition. MIT Press, CambridgeKneser R, Ney H (1995) Improved backing-off for N-gram language modeling. In: International conference on acoustics, speech and signal processing (ICASSP ’95), IEEE Computer Society, Los Alamitos, vol. 1, pp. 181–184, https://doi.org/10.1109/ICASSP.1995.479394Kozielski M, Forster J, Ney H (2012) Moment-based image normalization for handwritten text recognition. In: Proceedings of the 2012 international conference on frontiers in handwriting recognition, ICFHR ’12, pp 256–261. IEEE Computer Society, Washington. https://doi.org/10.1109/ICFHR.2012.236Lavrenko V, Rath TM, Manmatha R (2004) Holistic word recognition for handwritten historical documents. In: First Proceedings of international workshop on document image analysis for libraries, 2004, pp 278–287. https://doi.org/10.1109/DIAL.2004.1263256Manning CD, Raghavan P, Schutze H (2008) Introduction to information retrieval. Cambridge University Press, New YorkMarti UV, Bunke H (2002) The iam-database: an english sentence database for offline handwriting recognition. Int J Doc Anal Recogn 5:39–46. https://doi.org/10.1007/s100320200071Noya-García E, Toselli AH, Vidal E (2017) Simple and effective multi-word query spotting in handwritten text images, pp 76–84. Springer International Publishing, Cham. https://doi.org/10.1007/978-3-319-58838-4_9Pratikakis I, Zagoris K, Gatos B, Louloudis G, Stamatopoulos N (2014) ICFHR 2014 competition on handwritten keyword spotting (h-kws 2014). In: 14th International conference on frontiers in handwriting recognition (ICFHR), 2014, pp 814–819Puigcerver J, Toselli AH, Vidal E (2015) Icdar2015 competition on keyword spotting for handwritten documents. In: 13th international conference on document analysis and recognition (ICDAR), 2015, pp 1176–1180Riba P, Almazn J, Forns A, Fernndez-Mota D, Valveny E, Llads J (2014) e-crowds: a mobile platform for browsing and searching in historical demography-related manuscripts. In: 14th International conference on frontiers in handwriting recognition (ICFHR), 2014, pp 228–233. https://doi.org/10.1109/ICFHR.2014.46Robertson S (2008) A new interpretation of average precision. In: Proceedings of the international ACM SIGIR conference on research and development in information retrieval (SIGIR ’08), pp 689–690. ACM, New York. https://doi.org/10.1145/1390334.1390453Romero V, Toselli AH, Vidal E (2012) Multimodal interactive handwritten text transcription. Series in machine perception and artificial intelligence (MPAI). World Scientific Publishing, SingaporeSánchez JA, Romero V, Toselli AH, Vidal E (2016) ICFHR2016 competition on handwritten text recognition on the READ dataset. In: 15th International conference on frontiers in handwriting recognition (ICFHR’16), pp 630–635. https://doi.org/10.1109/ICFHR.2016.0120Toselli A, Vidal E (2015) Handwritten text recognition results on the Bentham collection with improved classical N-Gram-HMM methods. In: 3rd International workshop on historical document imaging and processing (HIP15), pp 15–22Toselli AH, Juan A, Keysers D, González J, Salvador I, Ney H, Vidal E, Casacuberta F (2004) Integrated Handwriting Recognition and Interpretation using Finite-State Models. Int J Pattern Recogn Artif Intell 18(4):519–539Toselli AH, Vidal E, Romero V, Frinken V (2016) HMM word graph based keyword spotting in handwritten document images. Inf Sci 370(C):497–518. https://doi.org/10.1016/j.ins.2016.07.063Vidal E, Toselli AH, Puigcerver J (2015) High performance query-by-example keyword spotting using query-by-string techniques. In: Proceedings of 13th ICDAR, pp 741–745Vidal E, Toselli AH, Puigcerver J (2017) Lexicon-based probabilistic keyword spotting in handwritten text images (to be published)Vinciarelli A, Bengio S, Bunke H (2004) Off-line recognition of unconstrained handwritten texts using HMMs and statistical language models. IEEE Trans Pattern Anal Mach Intell 26(6):709–720Young S, Evermann G, Gales M, Hain T, Kershaw D (2009) The HTK book: hidden markov models toolkit V3.4. Microsoft Corporation and Cambridge Research Laboratory Ltd, CambridgeYoung S, Odell J, Ollason D, Valtchev V, Woodland P (1997) The HTK book: hidden markov models toolkit V2.1. Cambridge Research Laboratory Ltd, CambridgeZhu M (2004) Recall, precision and average precision. Working paper 2004-09 Department of Statistics and Actuarial Science–University of Waterlo

Reconocimiento automático de un censo histórico impreso sin recursos lingüísticos

[ES] El reconocimiento automático de documentos históricos impresos es actualmente un problema resuelto para muchas colecciones de datos. Sin embargo, los sistemas de reconocimiento automático de documentos históricos impresos aún deben resolver varios obstáculos inherentes al trabajo con documentos antiguos. La degradación del papel o las manchas pueden aumentar la dificultad del correcto reconocimiento de los caracteres. No obstante, dichos problemas se pueden paliar utilizando recursos lingüísticos para entrenar buenos modelos de lenguaje que disminuyan la tasa de error de los caracteres. En cambio, hay muchas colecciones como la que se presenta en este trabajo, compuestas por tablas que contienen principalmente números y nombres propios, para las que no se dispone. En este trabajo se muestra que el reconocimiento automático puede realizarse con éxito para una colección de documentos sin utilizar ningún recurso lingüístico. Este proyecto cubre la extracción de información y el proceso de OCR dirigido, especialmente diseñados para el reconocimiento automático de un censo español del siglo XIX, registrado en documentos impresos. Muchos de los problemas relacionados con los documentos históricos se resuelven utilizando una combinación de técnicas clásicas de visión por computador y aprendizaje neuronal profundo. Los errores, como los caracteres mal reconocidos, son detectados y corregidos gracias a la información redundante que contiene el censo. Dada la importancia de este censo español para la realización de estudios demográficos, este trabajo da un paso más e introduce un modelo demostrador que facilita la investigación sobre este corpus mediante la indexación de los datos.[EN] Automatic recognition of typeset historical documents is currently a solved problem for many collections of data. However, systems for automatic recognition of typeset historical documents still need to address several issues inherent to working with this kind of documents. Degradation of the paper or smudges can increase the difficulty of correctly recognizing characters, problems that can be alleviated by using linguistic resources for training good language models which decrease the character error rate. Nonetheless, there are many collections such as the one presented in this paper, composed of tables that contain mainly numbers and proper names, for which a language model is neither available nor useful. This paper illustrates that automatic recognition can be done successfully for a collection of documents without using any linguistic resources. The paper covers the information extraction and the targeted OCR process, specially designed for the automatic recognition of a Spanish census from the XIX century, registered in printed documents. Many of the problems related to historical documents are overcame by using a combination of classical computer vision techniques and deep learning. Errors, such as miss-recognized characters, are detected and corrected thanks to redundant information that the census contains. Given the importance of this Spanish census for conducting demographic studies, this paper goes a step forward and introduces a demonstrator model to facilitate researching on this corpus by indexing the data.This work has been partially supported by the BBVA Fundation, as a collaboration between the PRHLT team in charge of the HisClima project and the ESPAREL project.Anitei, D. (2021). Reconocimiento automático de un censo histórico impreso sin recursos lingüísticos. Universitat Politècnica de València. http://hdl.handle.net/10251/172694TFG

Neural text line extraction in historical documents: a two-stage clustering approach

Accessibility of the valuable cultural heritage which is hidden in countless scanned historical documents is the motivation for the presented dissertation. The developed (fully automatic) text line extraction methodology combines state-of-the-art machine learning techniques and modern image processing methods. It demonstrates its quality by outperforming several other approaches on a couple of benchmarking datasets. The method is already being used by a wide audience of researchers from different disciplines and thus contributes its (small) part to the aforementioned goal.Das Erschließen des unermesslichen Wissens, welches in unzähligen gescannten historischen Dokumenten verborgen liegt, bildet die Motivation für die vorgelegte Dissertation. Durch das Verknüpfen moderner Verfahren des maschinellen Lernens und der klassischen Bildverarbeitung wird in dieser Arbeit ein vollautomatisches Verfahren zur Extraktion von Textzeilen aus historischen Dokumenten entwickelt. Die Qualität wird auf verschiedensten Datensätzen im Vergleich zu anderen Ansätzen nachgewiesen. Das Verfahren wird bereits durch eine Vielzahl von Forschern verschiedenster Disziplinen genutzt

Advances in Document Layout Analysis

[EN] Handwritten Text Segmentation (HTS) is a task within the Document Layout Analysis field that aims to detect and extract the different page regions of interest found in handwritten documents. HTS remains an active topic, that has gained importance with the years, due to the increasing demand to provide textual access to the myriads of handwritten document collections held by archives and libraries. This thesis considers HTS as a task that must be tackled in two specialized phases: detection and extraction. We see the detection phase fundamentally as a recognition problem that yields the vertical positions of each region of interest as a by-product. The extraction phase consists in calculating the best contour coordinates of the region using the position information provided by the detection phase. Our proposed detection approach allows us to attack both higher level regions: paragraphs, diagrams, etc., and lower level regions like text lines. In the case of text line detection we model the problem to ensure that the system's yielded vertical position approximates the fictitious line that connects the lower part of the grapheme bodies in a text line, commonly known as the baseline. One of the main contributions of this thesis, is that the proposed modelling approach allows us to include prior information regarding the layout of the documents being processed. This is performed via a Vertical Layout Model (VLM). We develop a Hidden Markov Model (HMM) based framework to tackle both region detection and classification as an integrated task and study the performance and ease of use of the proposed approach in many corpora. We review the modelling simplicity of our approach to process regions at different levels of information: text lines, paragraphs, titles, etc. We study the impact of adding deterministic and/or probabilistic prior information and restrictions via the VLM that our approach provides. Having a separate phase that accurately yields the detection position (base- lines in the case of text lines) of each region greatly simplifies the problem that must be tackled during the extraction phase. In this thesis we propose to use a distance map that takes into consideration the grey-scale information in the image. This allows us to yield extraction frontiers which are equidistant to the adjacent text regions. We study how our approach escalates its accuracy proportionally to the quality of the provided detection vertical position. Our extraction approach gives near perfect results when human reviewed baselines are provided.[ES] La Segmentación de Texto Manuscrito (STM) es una tarea dentro del campo de investigación de Análisis de Estructura de Documentos (AED) que tiene como objetivo detectar y extraer las diferentes regiones de interés de las páginas que se encuentran en documentos manuscritos. La STM es un tema de investigación activo que ha ganado importancia con los años debido a la creciente demanda de proporcionar acceso textual a las miles de colecciones de documentos manuscritos que se conservan en archivos y bibliotecas. Esta tesis entiende la STM como una tarea que debe ser abordada en dos fases especializadas: detección y extracción. Consideramos que la fase de detección es, fundamentalmente, un problema de clasificación cuyo subproducto son las posiciones verticales de cada región de interés. Por su parte, la fase de extracción consiste en calcular las mejores coordenadas de contorno de la región utilizando la información de posición proporcionada por la fase de detección. Nuestro enfoque de detección nos permite atacar tanto regiones de alto nivel (párrafos, diagramas¿) como regiones de nivel bajo (líneas de texto principalmente). En el caso de la detección de líneas de texto, modelamos el problema para asegurar que la posición vertical estimada por el sistema se aproxime a la línea ficticia que conecta la parte inferior de los cuerpos de los grafemas en una línea de texto, comúnmente conocida como línea base. Una de las principales aportaciones de esta tesis es que el enfoque de modelización propuesto nos permite incluir información conocida a priori sobre la disposición de los documentos que se están procesando. Esto se realiza mediante un Modelo de Estructura Vertical (MEV). Desarrollamos un marco de trabajo basado en los Modelos Ocultos de Markov (MOM) para abordar tanto la detección de regiones como su clasificación de forma integrada, así como para estudiar el rendimiento y la facilidad de uso del enfoque propuesto en numerosos corpus. Así mismo, revisamos la simplicidad del modelado de nuestro enfoque para procesar regiones en diferentes niveles de información: líneas de texto, párrafos, títulos, etc. Finalmente, estudiamos el impacto de añadir información y restricciones previas deterministas o probabilistas a través de el MEV propuesto que nuestro enfoque proporciona. Disponer de un método independiente que obtiene con precisión la posición de cada región detectada (líneas base en el caso de las líneas de texto) simplifica enormemente el problema que debe abordarse durante la fase de extracción. En esta tesis proponemos utilizar un mapa de distancias que tiene en cuenta la información de escala de grises de la imagen. Esto nos permite obtener fronteras de extracción que son equidistantes a las regiones de texto adyacentes. Estudiamos como nuestro enfoque aumenta su precisión de manera proporcional a la calidad de la detección y descubrimos que da resultados casi perfectos cuando se le proporcionan líneas de base revisadas por humanos.[CA] La Segmentació de Text Manuscrit (STM) és una tasca dins del camp d'investigació d'Anàlisi d'Estructura de Documents (AED) que té com a objectiu detectar I extraure les diferents regions d'interès de les pàgines que es troben en documents manuscrits. La STM és un tema d'investigació actiu que ha guanyat importància amb els anys a causa de la creixent demanda per proporcionar accés textual als milers de col·leccions de documents manuscrits que es conserven en arxius i biblioteques. Aquesta tesi entén la STM com una tasca que ha de ser abordada en dues fases especialitzades: detecció i extracció. Considerem que la fase de detecció és, fonamentalment, un problema de classificació el subproducte de la qual són les posicions verticals de cada regió d'interès. Per la seva part, la fase d'extracció consisteix a calcular les millors coordenades de contorn de la regió utilitzant la informació de posició proporcionada per la fase de detecció. El nostre enfocament de detecció ens permet atacar tant regions d'alt nivell (paràgrafs, diagrames ...) com regions de nivell baix (línies de text principalment). En el cas de la detecció de línies de text, modelem el problema per a assegurar que la posició vertical estimada pel sistema s'aproximi a la línia fictícia que connecta la part inferior dels cossos dels grafemes en una línia de text, comunament coneguda com a línia base. Una de les principals aportacions d'aquesta tesi és que l'enfocament de modelització proposat ens permet incloure informació coneguda a priori sobre la disposició dels documents que s'estan processant. Això es realitza mitjançant un Model d'Estructura Vertical (MEV). Desenvolupem un marc de treball basat en els Models Ocults de Markov (MOM) per a abordar tant la detecció de regions com la seva classificació de forma integrada, així com per a estudiar el rendiment i la facilitat d'ús de l'enfocament proposat en nombrosos corpus. Així mateix, revisem la simplicitat del modelatge del nostre enfocament per a processar regions en diferents nivells d'informació: línies de text, paràgrafs, títols, etc. Finalment, estudiem l'impacte d'afegir informació i restriccions prèvies deterministes o probabilistes a través del MEV que el nostre mètode proporciona. Disposar d'un mètode independent que obté amb precisió la posició de cada regió detectada (línies base en el cas de les línies de text) simplifica enormement el problema que ha d'abordar-se durant la fase d'extracció. En aquesta tesi proposem utilitzar un mapa de distàncies que té en compte la informació d'escala de grisos de la imatge. Això ens permet obtenir fronteres d'extracció que són equidistants de les regions de text adjacents. Estudiem com el nostre enfocament augmenta la seva precisió de manera proporcional a la qualitat de la detecció i descobrim que dona resultats quasi perfectes quan se li proporcionen línies de base revisades per humans.Bosch Campos, V. (2020). Advances in Document Layout Analysis [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/138397TESI

Spoken command recognition for robotics

In this thesis, I investigate spoken command recognition technology for robotics. While high robustness is expected, the distant and noisy conditions in which the system has to operate make the task very challenging. Unlike commercial systems which all rely on a "wake-up" word to initiate the interaction, the pipeline proposed here directly detect and recognizes commands from the continuous audio stream. In order to keep the task manageable despite low-resource conditions, I propose to focus on a limited set of commands, thus trading off flexibility of the system against robustness. Domain and speaker adaptation strategies based on a multi-task regularization paradigm are first explored. More precisely, two different methods are proposed which rely on a tied loss function which penalizes the distance between the output of several networks. The first method considers each speaker or domain as a task. A canonical task-independent network is jointly trained with task-dependent models, allowing both types of networks to improve by learning from one another. While an improvement of 3.2% on the frame error rate (FER) of the task-independent network is obtained, this only partially carried over to the phone error rate (PER), with 1.5% of improvement. Similarly, a second method explored the parallel training of the canonical network with a privileged model having access to i-vectors. This method proved less effective with only 1.2% of improvement on the FER. In order to make the developed technology more accessible, I also investigated the use of a sequence-to-sequence (S2S) architecture for command classification. The use of an attention-based encoder-decoder model reduced the classification error by 40% relative to a strong convolutional neural network (CNN)-hidden Markov model (HMM) baseline, showing the relevance of S2S architectures in such context. In order to improve the flexibility of the trained system, I also explored strategies for few-shot learning, which allow to extend the set of commands with minimum requirements in terms of data. Retraining a model on the combination of original and new commands, I managed to achieve 40.5% of accuracy on the new commands with only 10 examples for each of them. This scores goes up to 81.5% of accuracy with a larger set of 100 examples per new command. An alternative strategy, based on model adaptation achieved even better scores, with 68.8% and 88.4% of accuracy with 10 and 100 examples respectively, while being faster to train. This high performance is obtained at the expense of the original categories though, on which the accuracy deteriorated. Those results are very promising as the methods allow to easily extend an existing S2S model with minimal resources. Finally, a full spoken command recognition system (named iCubrec) has been developed for the iCub platform. The pipeline relies on a voice activity detection (VAD) system to propose a fully hand-free experience. By segmenting only regions that are likely to contain commands, the VAD module also allows to reduce greatly the computational cost of the pipeline. Command candidates are then passed to the deep neural network (DNN)-HMM command recognition system for transcription. The VoCub dataset has been specifically gathered to train a DNN-based acoustic model for our task. Through multi-condition training with the CHiME4 dataset, an accuracy of 94.5% is reached on VoCub test set. A filler model, complemented by a rejection mechanism based on a confidence score, is finally added to the system to reject non-command speech in a live demonstration of the system

Mathematical Expression Recognition based on Probabilistic Grammars

[EN] Mathematical notation is well-known and used all over the world. Humankind has evolved from simple methods representing countings to current well-defined math notation able to account for complex problems. Furthermore, mathematical expressions constitute a universal language in scientific fields, and many information resources containing mathematics have been created during the last decades. However, in order to efficiently access all that information, scientific documents have to be digitized or produced directly in electronic formats. Although most people is able to understand and produce mathematical information, introducing math expressions into electronic devices requires learning specific notations or using editors. Automatic recognition of mathematical expressions aims at filling this gap between the knowledge of a person and the input accepted by computers. This way, printed documents containing math expressions could be automatically digitized, and handwriting could be used for direct input of math notation into electronic devices. This thesis is devoted to develop an approach for mathematical expression recognition. In this document we propose an approach for recognizing any type of mathematical expression (printed or handwritten) based on probabilistic grammars. In order to do so, we develop the formal statistical framework such that derives several probability distributions. Along the document, we deal with the definition and estimation of all these probabilistic sources of information. Finally, we define the parsing algorithm that globally computes the most probable mathematical expression for a given input according to the statistical framework. An important point in this study is to provide objective performance evaluation and report results using public data and standard metrics. We inspected the problems of automatic evaluation in this field and looked for the best solutions. We also report several experiments using public databases and we participated in several international competitions. Furthermore, we have released most of the software developed in this thesis as open source. We also explore some of the applications of mathematical expression recognition. In addition to the direct applications of transcription and digitization, we report two important proposals. First, we developed mucaptcha, a method to tell humans and computers apart by means of math handwriting input, which represents a novel application of math expression recognition. Second, we tackled the problem of layout analysis of structured documents using the statistical framework developed in this thesis, because both are two-dimensional problems that can be modeled with probabilistic grammars. The approach developed in this thesis for mathematical expression recognition has obtained good results at different levels. It has produced several scientific publications in international conferences and journals, and has been awarded in international competitions.[ES] La notación matemática es bien conocida y se utiliza en todo el mundo. La humanidad ha evolucionado desde simples métodos para representar cuentas hasta la notación formal actual capaz de modelar problemas complejos. Además, las expresiones matemáticas constituyen un idioma universal en el mundo científico, y se han creado muchos recursos que contienen matemáticas durante las últimas décadas. Sin embargo, para acceder de forma eficiente a toda esa información, los documentos científicos han de ser digitalizados o producidos directamente en formatos electrónicos. Aunque la mayoría de personas es capaz de entender y producir información matemática, introducir expresiones matemáticas en dispositivos electrónicos requiere aprender notaciones especiales o usar editores. El reconocimiento automático de expresiones matemáticas tiene como objetivo llenar ese espacio existente entre el conocimiento de una persona y la entrada que aceptan los ordenadores. De este modo, documentos impresos que contienen fórmulas podrían digitalizarse automáticamente, y la escritura se podría utilizar para introducir directamente notación matemática en dispositivos electrónicos. Esta tesis está centrada en desarrollar un método para reconocer expresiones matemáticas. En este documento proponemos un método para reconocer cualquier tipo de fórmula (impresa o manuscrita) basado en gramáticas probabilísticas. Para ello, desarrollamos el marco estadístico formal que deriva varias distribuciones de probabilidad. A lo largo del documento, abordamos la definición y estimación de todas estas fuentes de información probabilística. Finalmente, definimos el algoritmo que, dada cierta entrada, calcula globalmente la expresión matemática más probable de acuerdo al marco estadístico. Un aspecto importante de este trabajo es proporcionar una evaluación objetiva de los resultados y presentarlos usando datos públicos y medidas estándar. Por ello, estudiamos los problemas de la evaluación automática en este campo y buscamos las mejores soluciones. Asimismo, presentamos diversos experimentos usando bases de datos públicas y hemos participado en varias competiciones internacionales. Además, hemos publicado como código abierto la mayoría del software desarrollado en esta tesis. También hemos explorado algunas de las aplicaciones del reconocimiento de expresiones matemáticas. Además de las aplicaciones directas de transcripción y digitalización, presentamos dos propuestas importantes. En primer lugar, desarrollamos mucaptcha, un método para discriminar entre humanos y ordenadores mediante la escritura de expresiones matemáticas, el cual representa una novedosa aplicación del reconocimiento de fórmulas. En segundo lugar, abordamos el problema de detectar y segmentar la estructura de documentos utilizando el marco estadístico formal desarrollado en esta tesis, dado que ambos son problemas bidimensionales que pueden modelarse con gramáticas probabilísticas. El método desarrollado en esta tesis para reconocer expresiones matemáticas ha obtenido buenos resultados a diferentes niveles. Este trabajo ha producido varias publicaciones en conferencias internacionales y revistas, y ha sido premiado en competiciones internacionales.[CA] La notació matemàtica és ben coneguda i s'utilitza a tot el món. La humanitat ha evolucionat des de simples mètodes per representar comptes fins a la notació formal actual capaç de modelar problemes complexos. A més, les expressions matemàtiques constitueixen un idioma universal al món científic, i s'han creat molts recursos que contenen matemàtiques durant les últimes dècades. No obstant això, per accedir de forma eficient a tota aquesta informació, els documents científics han de ser digitalitzats o produïts directament en formats electrònics. Encara que la majoria de persones és capaç d'entendre i produir informació matemàtica, introduir expressions matemàtiques en dispositius electrònics requereix aprendre notacions especials o usar editors. El reconeixement automàtic d'expressions matemàtiques té per objectiu omplir aquest espai existent entre el coneixement d'una persona i l'entrada que accepten els ordinadors. D'aquesta manera, documents impresos que contenen fórmules podrien digitalitzar-se automàticament, i l'escriptura es podria utilitzar per introduir directament notació matemàtica en dispositius electrònics. Aquesta tesi està centrada en desenvolupar un mètode per reconèixer expressions matemàtiques. En aquest document proposem un mètode per reconèixer qualsevol tipus de fórmula (impresa o manuscrita) basat en gramàtiques probabilístiques. Amb aquesta finalitat, desenvolupem el marc estadístic formal que deriva diverses distribucions de probabilitat. Al llarg del document, abordem la definició i estimació de totes aquestes fonts d'informació probabilística. Finalment, definim l'algorisme que, donada certa entrada, calcula globalment l'expressió matemàtica més probable d'acord al marc estadístic. Un aspecte important d'aquest treball és proporcionar una avaluació objectiva dels resultats i presentar-los usant dades públiques i mesures estàndard. Per això, estudiem els problemes de l'avaluació automàtica en aquest camp i busquem les millors solucions. Així mateix, presentem diversos experiments usant bases de dades públiques i hem participat en diverses competicions internacionals. A més, hem publicat com a codi obert la majoria del software desenvolupat en aquesta tesi. També hem explorat algunes de les aplicacions del reconeixement d'expressions matemàtiques. A més de les aplicacions directes de transcripció i digitalització, presentem dues propostes importants. En primer lloc, desenvolupem mucaptcha, un mètode per discriminar entre humans i ordinadors mitjançant l'escriptura d'expressions matemàtiques, el qual representa una nova aplicació del reconeixement de fórmules. En segon lloc, abordem el problema de detectar i segmentar l'estructura de documents utilitzant el marc estadístic formal desenvolupat en aquesta tesi, donat que ambdós són problemes bidimensionals que poden modelar-se amb gramàtiques probabilístiques. El mètode desenvolupat en aquesta tesi per reconèixer expressions matemàtiques ha obtingut bons resultats a diferents nivells. Aquest treball ha produït diverses publicacions en conferències internacionals i revistes, i ha sigut premiat en competicions internacionals.Álvaro Muñoz, F. (2015). Mathematical Expression Recognition based on Probabilistic Grammars [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/51665TESI