Arabic Printed Word Recognition Using Windowed Bernoulli HMMs

[EN] Hidden Markov Models (HMMs) are now widely used for off-line text recognition in many languages and, in particular, Arabic. In previous work, we proposed to directly use columns of raw, binary image pixels, which are directly fed into embedded Bernoulli (mixture) HMMs, that is, embedded HMMs in which the emission probabilities are modeled with Bernoulli mixtures. The idea was to by-pass feature extraction and to ensure that no discriminative information is filtered out during feature extraction, which in some sense is integrated into the recognition model. More recently, we extended the column bit vectors by means of a sliding window of adequate width to better capture image context at each horizontal position of the word image. However, these models might have limited capability to properly model vertical image distortions. In this paper, we have considered three methods of window repositioning after window extraction to overcome this limitation. Each sliding window is translated (repositioned) to align its center to the center of mass. Using this approach, state-of-art results are reported on the Arabic Printed Text Recognition (APTI) database.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement no 287755. Also supported by the Spanish Government (Plan E, iTrans2 TIN2009-14511 and AECID 2011/2012 grant).Alkhoury, I.; Giménez Pastor, A.; Juan Císcar, A.; Andrés Ferrer, J. (2013). Arabic Printed Word Recognition Using Windowed Bernoulli HMMs. Lecture Notes in Computer Science. 8156:330-339. https://doi.org/10.1007/978-3-642-41181-6_34S3303398156Dehghan, M., et al.: Handwritten Farsi (Arabic) word recognition: a holistic approach using discrete HMM. Pattern Recognition 34(5), 1057–1065 (2001), http://www.sciencedirect.com/science/article/pii/S0031320300000510Giménez, A., Juan, A.: Embedded Bernoulli Mixture HMMs for Handwritten Word Recognition. In: ICDAR 2009, Barcelona, Spain, pp. 896–900 (July 2009)Giménez, A., Khoury, I., Juan, A.: Windowed Bernoulli Mixture HMMs for Arabic Handwritten Word Recognition. In: ICFHR 2010, Kolkata, India, pp. 533–538 (November 2010)Grosicki, E., El Abed, H.: ICDAR 2009 Handwriting Recognition Competition. In: ICDAR 2009, Barcelona, Spain, pp. 1398–1402 (July 2009)Günter, S., et al.: HMM-based handwritten word recognition: on the optimization of the number of states, training iterations and Gaussian components. Pattern Recognition 37, 2069–2079 (2004)Märgner, V., El Abed, H.: ICDAR 2007 - Arabic Handwriting Recognition Competition. In: ICDAR 2007, Curitiba, Brazil, pp. 1274–1278 (September 2007)Märgner, V., El Abed, H.: ICDAR 2009 Arabic Handwriting Recognition Competition. In: ICDAR 2009, Barcelona, Spain, pp. 1383–1387 (July 2009)Pechwitz, M., et al.: IFN/ENIT - database of handwritten Arabic words. In: CIFED 2002, Hammamet, Tunis, pp. 21–23 (October 2002)Rabiner, L., Juang, B.: Fundamentals of speech recognition. Prentice-Hall (1993)Slimane, F., et al.: A new arabic printed text image database and evaluation protocols. In: ICDAR 2009, pp. 946–950 (July 2009)Slimane, F., et al.: ICDAR 2011 - arabic recognition competition: Multi-font multi-size digitally represented text. In: ICDAR 2011 - Arabic Recognition Competition, pp. 1449–1453. IEEE (September 2011)Young, S.: et al.: The HTK Book. Cambridge University Engineering Department (1995

Window repositioning for Printed Arabic Recognition

[EN] Bernoulli HMMs are conventional HMMs in which the emission probabilities are modeled with Bernoulli mixtures. They have recently been applied, with good results, in off-line text recognition in many languages, in particular, Arabic. A key idea that has proven to be very effective in this application of Bernoulli HMMs is the use of a sliding window of adequate width for feature extraction. This idea has allowed us to obtain very competitive results in the recognition of both Arabic handwriting and printed text. Indeed, a system based on it ranked first at the ICDAR 2011 Arabic recognition competition on the Arabic Printed Text Image (APTI) database. More recently, this idea has been refined by using repositioning techniques for extracted windows, leading to further improvements in Arabic handwriting recognition. In the case of printed text, this refinement led to an improved system which ranked second at the ICDAR 2013 second competition on APTI, only at a marginal distance from the best system. In this work, we describe the development of this improved system. Following evaluation protocols similar to those of the competitions on APTI, exhaustive experiments are detailed from which state-of-the-art results are obtained.The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/ICT-287755) under grant agreement no. 287755. The research is also supported by the Spanish Government (Plan E, iTrans2 TIN2009-14511 and AECID 2011/2012 grant).Alkhoury, I.; Giménez Pastor, A.; Juan, A.; Andrés Ferrer, J. (2015). Window repositioning for Printed Arabic Recognition. Pattern Recognition Letters. 51:86-93. https://doi.org/10.1016/j.patrec.2014.08.009S86935

Novel geometric features for off-line writer identification

Writer identification is an important field in forensic document examination. Typically, a writer identification system consists of two main steps: feature extraction and matching and the performance depends significantly on the feature extraction step. In this paper, we propose a set of novel geometrical features that are able to characterize different writers. These features include direction, curvature, and tortuosity. We also propose an improvement of the edge-based directional and chain code-based features. The proposed methods are applicable to Arabic and English handwriting. We have also studied several methods for computing the distance between feature vectors when comparing two writers. Evaluation of the methods is performed using both the IAM handwriting database and the QUWI database for each individual feature reaching Top1 identification rates of 82 and 87 % in those two datasets, respectively. The accuracies achieved by Kernel Discriminant Analysis (KDA) are significantly higher than those observed before feature-level writer identification was implemented. The results demonstrate the effectiveness of the improved versions of both chain-code features and edge-based directional features