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Josep Llados and Enric Marti. 1999. Graph-edit algorithms for hand-drawn graphical document recognition and their automatic introduction. Machine Graphics & Vision journal, special issue on Graph transformation.
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Josep Llados, Enric Marti and Jaime Lopez-Krahe. 1999. A Hough-based method for hatched pattern detection in maps and diagrams. Proceeding of the Fifth Int. Conf. Document Analysis and Recognition ICDAR ’99.479–482.
Abstract: A hatched area is characterized by a set of parallel straight lines placed at regular intervals. In this paper, a Hough-based schema is introduced to recognize hatched areas in technical documents from attributed graph structures representing the document once it has been vectorized. Defining a Hough-based transform from a graph instead of the raster image allows to drastically reduce the processing time and, second, to obtain more reliable results because straight lines have already been detected in the vectorization step. A second advantage of the proposed method is that no assumptions must be made a priori about the slope and frequency of hatching patterns, but they are computed in run time for each hatched area.
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Josep Llados and Enric Marti. 1999. A graph-edit algorithm for hand-drawn graphical document recognition and their automatic introduction into CAD systems. Machine Graphics & Vision, 8, 195–211.
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Josep Llados, Horst Bunke and Enric Marti. 1996. Structural Recognition of hand drawn floor plans. VI National Symposium on Pattern Recognition and Image Analysis. Cordoba.
Abstract: A system to recognize hand drawn architectural drawings in a CAD environment has been deve- loped. In this paper we focus on its high level interpretation module. To interpret a floor plan, the system must identify several building elements, whose description is stored in a library of pat- terns, as well as their spatial relationships. We propose a structural approach based on subgraph isomorphism techniques to obtain a high-level interpretation of the document. The vectorized input document and the patterns to be recognized are represented by attributed graphs. Discrete relaxation techniques (AC4 algorithm) have been applied to develop the matching algorithm. The process has been divided in three steps: node labeling, local consistency and global consistency verification. The hand drawn creation causes disturbed line drawings with several accuracy errors, which must be taken into account. Here we have identified them and the AC4 algorithm has been adapted to manage them.
Keywords: Rotational Symmetry; Reflectional Symmetry; String Matching.
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Josep Llados, Horst Bunke and Enric Marti. 1997. Using Cyclic String Matching to Find Rotational and Reflectional Symmetries in Shapes. Intelligent Robots: Sensing, Modeling and Planning. World Scientific Press, 164–179.
Abstract: Dagstuhl Workshop
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Josep Llados, Horst Bunke and Enric Marti. 1997. Finding rotational symmetries by cyclic string matching. PRL, 18(14), 1435–1442.
Abstract: Symmetry is an important shape feature. In this paper, a simple and fast method to detect perfect and distorted rotational symmetries of 2D objects is described. The boundary of a shape is polygonally approximated and represented as a string. Rotational symmetries are found by cyclic string matching between two identical copies of the shape string. The set of minimum cost edit sequences that transform the shape string to a cyclically shifted version of itself define the rotational symmetry and its order. Finally, a modification of the algorithm is proposed to detect reflectional symmetries. Some experimental results are presented to show the reliability of the proposed algorithm
Keywords: Rotational symmetry; Reflectional symmetry; String matching
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Josep Llados, Horst Bunke and Enric Marti. 1996. Using cyclic string matching to find rotational and reflectional symmetric shapes. In R.C. Bolles, H.B.H.N., ed. Dagstuhl Seminar on Modelling and Planning for Sensor–based Intelligent Robot Systems. Saarbrucken (Germany)., World Scientific.
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Dimosthenis Karatzas and Ch. Lioutas. 1998. Software Package Development for Electron Diffraction Image Analysis. Proceedings of the XIV Solid State Physics National Conference.
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Debora Gil, Jordi Gonzalez and Gemma Sanchez, eds. 2007. Computer Vision: Advances in Research and Development. Bellaterra (Spain), UAB. (2.)
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Miquel Ferrer, Dimosthenis Karatzas, Ernest Valveny, I. Bardaji and Horst Bunke. 2011. A Generic Framework for Median Graph Computation based on a Recursive Embedding Approach. CVIU, 115(7), 919–928.
Abstract: The median graph has been shown to be a good choice to obtain a represen- tative of a set of graphs. However, its computation is a complex problem. Recently, graph embedding into vector spaces has been proposed to obtain approximations of the median graph. The problem with such an approach is how to go from a point in the vector space back to a graph in the graph space. The main contribution of this paper is the generalization of this previ- ous method, proposing a generic recursive procedure that permits to recover the graph corresponding to a point in the vector space, introducing only the amount of approximation inherent to the use of graph matching algorithms. In order to evaluate the proposed method, we compare it with the set me- dian and with the other state-of-the-art embedding-based methods for the median graph computation. The experiments are carried out using four dif- ferent databases (one semi-artificial and three containing real-world data). Results show that with the proposed approach we can obtain better medi- ans, in terms of the sum of distances to the training graphs, than with the previous existing methods.
Keywords: Median Graph, Graph Embedding, Graph Matching, Structural Pattern Recognition
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