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Jaume Gibert, Ernest Valveny and Horst Bunke. 2012. Graph Embedding in Vector Spaces by Node Attribute Statistics. PR, 45(9), 3072–3083.
Abstract: Graph-based representations are of broad use and applicability in pattern recognition. They exhibit, however, a major drawback with regards to the processing tools that are available in their domain. Graphembedding into vectorspaces is a growing field among the structural pattern recognition community which aims at providing a feature vector representation for every graph, and thus enables classical statistical learning machinery to be used on graph-based input patterns. In this work, we propose a novel embedding methodology for graphs with continuous nodeattributes and unattributed edges. The approach presented in this paper is based on statistics of the node labels and the edges between them, based on their similarity to a set of representatives. We specifically deal with an important issue of this methodology, namely, the selection of a suitable set of representatives. In an experimental evaluation, we empirically show the advantages of this novel approach in the context of different classification problems using several databases of graphs.
Keywords: Structural pattern recognition; Graph embedding; Data clustering; Graph classification
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Jon Almazan, Albert Gordo, Alicia Fornes and Ernest Valveny. 2012. Efficient Exemplar Word Spotting. 23rd British Machine Vision Conference.67.1–67.11.
Abstract: In this paper we propose an unsupervised segmentation-free method for word spotting in document images.
Documents are represented with a grid of HOG descriptors, and a sliding window approach is used to locate the document regions that are most similar to the query. We use the exemplar SVM framework to produce a better representation of the query in an unsupervised way. Finally, the document descriptors are precomputed and compressed with Product Quantization. This offers two advantages: first, a large number of documents can be kept in RAM memory at the same time. Second, the sliding window becomes significantly faster since distances between quantized HOG descriptors can be precomputed. Our results significantly outperform other segmentation-free methods in the literature, both in accuracy and in speed and memory usage.
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Jon Almazan, David Fernandez, Alicia Fornes, Josep Llados and Ernest Valveny. 2012. A Coarse-to-Fine Approach for Handwritten Word Spotting in Large Scale Historical Documents Collection. 13th International Conference on Frontiers in Handwriting Recognition.453–458.
Abstract: In this paper we propose an approach for word spotting in handwritten document images. We state the problem from a focused retrieval perspective, i.e. locating instances of a query word in a large scale dataset of digitized manuscripts. We combine two approaches, namely one based on word segmentation and another one segmentation-free. The first approach uses a hashing strategy to coarsely prune word images that are unlikely to be instances of the query word. This process is fast but has a low precision due to the errors introduced in the segmentation step. The regions containing candidate words are sent to the second process based on a state of the art technique from the visual object detection field. This discriminative model represents the appearance of the query word and computes a similarity score. In this way we propose a coarse-to-fine approach achieving a compromise between efficiency and accuracy. The validation of the model is shown using a collection of old handwritten manuscripts. We appreciate a substantial improvement in terms of precision regarding the previous proposed method with a low computational cost increase.
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Jon Almazan, Alicia Fornes and Ernest Valveny. 2012. A non-rigid appearance model for shape description and recognition. PR, 45(9), 3105–3113.
Abstract: In this paper we describe a framework to learn a model of shape variability in a set of patterns. The framework is based on the Active Appearance Model (AAM) and permits to combine shape deformations with appearance variability. We have used two modifications of the Blurred Shape Model (BSM) descriptor as basic shape and appearance features to learn the model. These modifications permit to overcome the rigidity of the original BSM, adapting it to the deformations of the shape to be represented. We have applied this framework to representation and classification of handwritten digits and symbols. We show that results of the proposed methodology outperform the original BSM approach.
Keywords: Shape recognition; Deformable models; Shape modeling; Hand-drawn recognition
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Marçal Rusiñol, R.Roset, Josep Llados and C.Montaner. 2011. Automatic Index Generation of Digitized Map Series by Coordinate Extraction and Interpretation. In Proceedings of the Sixth International Workshop on Digital Technologies in Cartographic Heritage.
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Jean-Marc Ogier, Wenyin Liu and Josep Llados, eds. 2010. Graphics Recognition: Achievements, Challenges, and Evolution. Springer Link. (LNCS.)
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Salvatore Tabbone, Oriol Ramos Terrades and S. Barrat. 2008. Histogram of radon transform. A useful descriptor for shape retrieval. 19th International Conference on Pattern Recognition.1–4.
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T.O. Nguyen, Salvatore Tabbone, Oriol Ramos Terrades and A.T. Thierry. 2008. Proposition d'un descripteur de formes et du modèle vectoriel pour la recherche de symboles. Colloque International Francophone sur l'Ecrit et le Document.79–84.
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H. Chouaib, Salvatore Tabbone, Oriol Ramos Terrades, F. Cloppet, N. Vincent and A.T. Thierry Paquet. 2008. Sélection de Caractéristiques à partir d'un algorithme génétique et d'une combinaison de classifieurs Adaboost. Colloque International Francophone sur l'Ecrit et le Document.181–186.
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T.O. Nguyen, Salvatore Tabbone and Oriol Ramos Terrades. 2008. Symbol Descriptor Based on Shape Context and Vector Model of Information Retrieval. Proceedings of the 8th IAPR International Workshop on Document Analysis Systems,.191–197.
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