Identification of the initial rule-base of a multi-stroke fuzzy-based character recognition method with meta-heuristic techniques

This paper summarizes the basic concept of the designed a fuzzy-based character recognition algorithm family and the results of the optimization of its rule-base with two various meta-heuristic methods, the Imperialist Competitive Algorithm and the bacterial evolutionary algorithm. The results are presented and compared with two other methods from literature after a short overview of the recognition algorithm

Reconnaissance de l'écriture manuscrite en-ligne par approche combinant systèmes à vastes marges et modèles de Markov cachés

Handwriting recognition is one of the leading applications of pattern recognition and machine learning. Despite having some limitations, handwriting recognition systems have been used as an input method of many electronic devices and helps in the automation of many manual tasks requiring processing of handwriting images. In general, a handwriting recognition system comprises three functional components; preprocessing, recognition and post-processing. There have been improvements made within each component in the system. However, to further open the avenues of expanding its applications, specific improvements need to be made in the recognition capability of the system. Hidden Markov Model (HMM) has been the dominant methods of recognition in handwriting recognition in offline and online systems. However, the use of Gaussian observation densities in HMM and representational model for word modeling often does not lead to good classification. Hybrid of Neural Network (NN) and HMM later improves word recognition by taking advantage of NN discriminative property and HMM representational capability. However, the use of NN does not optimize recognition capability as the use of Empirical Risk minimization (ERM) principle in its training leads to poor generalization. In this thesis, we focus on improving the recognition capability of a cursive online handwritten word recognition system by using an emerging method in machine learning, the support vector machine (SVM). We first evaluated SVM in isolated character recognition environment using IRONOFF and UNIPEN character databases. SVM, by its use of principle of structural risk minimization (SRM) have allowed simultaneous optimization of representational and discriminative capability of the character recognizer. We finally demonstrate the various practical issues in using SVM within a hybrid setting with HMM. In addition, we tested the hybrid system on the IRONOFF word database and obtained favourable results.Nos travaux concernent la reconnaissance de l'écriture manuscrite qui est l'un des domaines de prédilection pour la reconnaissance des formes et les algorithmes d'apprentissage. Dans le domaine de l'écriture en-ligne, les applications concernent tous les dispositifs de saisie permettant à un usager de communiquer de façon transparente avec les systèmes d'information. Dans ce cadre, nos travaux apportent une contribution pour proposer une nouvelle architecture de reconnaissance de mots manuscrits sans contrainte de style. Celle-ci se situe dans la famille des approches hybrides locale/globale où le paradigme de la segmentation/reconnaissance va se trouver résolu par la complémentarité d'un système de reconnaissance de type discriminant agissant au niveau caractère et d'un système par approche modèle pour superviser le niveau global. Nos choix se sont portés sur des Séparateurs à Vastes Marges (SVM) pour le classifieur de caractères et sur des algorithmes de programmation dynamique, issus d'une modélisation par Modèles de Markov Cachés (HMM). Cette combinaison SVM/HMM est unique dans le domaine de la reconnaissance de l'écriture manuscrite. Des expérimentations ont été menées, d'abord dans un cadre de reconnaissance de caractères isolés puis sur la base IRONOFF de mots cursifs. Elles ont montré la supériorité des approches SVM par rapport aux solutions à bases de réseaux de neurones à convolutions (Time Delay Neural Network) que nous avions développées précédemment, et leur bon comportement en situation de reconnaissance de mots

Visual pattern recognition using neural networks

Neural networks have been widely studied in a number of fields, such as neural architectures, neurobiology, statistics of neural network and pattern classification. In the field of pattern classification, neural network models are applied on numerous applications, for instance, character recognition, speech recognition, and object recognition. Among these, character recognition is commonly used to illustrate the feature and classification characteristics of neural networks. In this dissertation, the theoretical foundations of artificial neural networks are first reviewed and existing neural models are studied. The Adaptive Resonance Theory (ART) model is improved to achieve more reasonable classification results. Experiments in applying the improved model to image enhancement and printed character recognition are discussed and analyzed. We also study the theoretical foundation of Neocognitron in terms of feature extraction, convergence in training, and shift invariance. We investigate the use of multilayered perceptrons with recurrent connections as the general purpose modules for image operations in parallel architectures. The networks are trained to carry out classification rules in image transformation. The training patterns can be derived from user-defmed transformations or from loading the pair of a sample image and its target image when the prior knowledge of transformations is unknown. Applications of our model include image smoothing, enhancement, edge detection, noise removal, morphological operations, image filtering, etc. With a number of stages stacked up together we are able to apply a series of operations on the image. That is, by providing various sets of training patterns the system can adapt itself to the concatenated transformation. We also discuss and experiment in applying existing neural models, such as multilayered perceptron, to realize morphological operations and other commonly used imaging operations. Some new neural architectures and training algorithms for the implementation of morphological operations are designed and analyzed. The algorithms are proven correct and efficient. The proposed morphological neural architectures are applied to construct the feature extraction module of a personal handwritten character recognition system. The system was trained and tested with scanned image of handwritten characters. The feasibility and efficiency are discussed along with the experimental results

Recognition of handwritten Arabic characters

The subject of handwritten character recognition has been receiving considerable attention in recent years due to the increased dependence on computers. Several methods for recognizing Latin, Chinese as well as Kanji characters have been proposed. However, work on recognition of Arabic characters has been relatively sparse. Techniques developed for recognizing characters in other languages can not be used for Arabic since the nature of Arabic characters is different. The shape of a character is a function of its location within a word where each character can have two to four different forms. Most of the techniques proposed to date for recognizing Arabic characters have relied on structural and topographic approaches. This thesis introduces a decision-theoretic approach to solve the problem. The proposed method involves, as a first step, digitization of the segmented character. The secondary part of the character (dots and zigzags) are then isolated and identified separately thereby reducing the recognition issue to a 20 class problem or less for each of the character forms. The moments of the horizontal and vertical projections of the remaining primary characters are calculated and normalized with respect to the zero order moment. Simple measures of shape are obtained from the normalized moments and incorporated into a feature vector. Classification is accomplished using quadratic discriminant functions. The approach was evaluated using isolated, handwritten characters from a data base established for this purpose. The classification rates varied from 97.5% to 100% depending on the form of the characters. These results indicate that the technique offers significantly better classification rates in comparison with existing methods

Adaptive combinations of classifiers with application to on-line handwritten character recognition

Classifier combining is an effective way of improving classification performance. User adaptation is clearly another valid approach for improving performance in a user-dependent system, and even though adaptation is usually performed on the classifier level, also adaptive committees can be very effective. Adaptive committees have the distinct ability of performing adaptation without detailed knowledge of the classifiers. Adaptation can therefore be used even with classification systems that intrinsically are not suited for adaptation, whether that be due to lack of access to the workings of the classifier or simply a classification scheme not suitable for continuous learning. This thesis proposes methods for adaptive combination of classifiers in the setting of on-line handwritten character recognition. The focal part of the work introduces adaptive classifier combination schemes, of which the two most prominent ones are the Dynamically Expanding Context (DEC) committee and the Class-Confidence Critic Combining (CCCC) committee. Both have been shown to be capable of successful adaptation to the user in the task of on-line handwritten character recognition. Particularly the highly modular CCCC framework has shown impressive performance also in a doubly-adaptive setting of combining adaptive classifiers by using an adaptive committee. In support of this main topic of the thesis, some discussion on a methodology for deducing correct character labeling from user actions is presented. Proper labeling is paramount for effective adaptation, and deducing the labels from the user's actions is necessary to perform adaptation transparently to the user. In that way, the user does not need to give explicit feedback on the correctness of the recognition results. Also, an overview is presented of adaptive classification methods for single-classifier adaptation in handwritten character recognition developed at the Laboratory of Computer and Information Science of the Helsinki University of Technology, CIS-HCR. Classifiers based on the CIS-HCR system have been used in the adaptive committee experiments as both member classifiers and to provide a reference level. Finally, two distinct approaches for improving the performance of committee classifiers further are discussed. Firstly, methods for committee rejection are presented and evaluated. Secondly, measures of classifier diversity for classifier selection, based on the concept of diversity of errors, are presented and evaluated. The topic of this thesis hence covers three important aspects of pattern recognition: on-line adaptation, combining classifiers, and a practical evaluation setting of handwritten character recognition. A novel approach combining these three core ideas has been developed and is presented in the introductory text and the included publications. To reiterate, the main contributions of this thesis are: 1) introduction of novel adaptive committee classification methods, 2) introduction of novel methods for measuring classifier diversity, 3) presentation of some methods for implementing committee rejection, 4) discussion and introduction of a method for effective label deduction from on-line user actions, and as a side-product, 5) an overview of the CIS-HCR adaptive on-line handwritten character recognition system.Luokittimien yhdistäminen komitealuokittimella on tehokas keino luokitustarkkuuden parantamiseen. Laskentatehon jatkuva kasvu tekee myös useiden luokittimien yhtäaikaisesta käytöstä yhä varteenotettavamman vaihtoehdon. Järjestelmän adaptoituminen (mukautuminen) käyttäjään on toinen hyvä keino käyttäjäriippumattoman järjestelmän tarkkuuden parantantamiseksi. Vaikka adaptaatio yleensä toteutetaan luokittimen tasolla, myös adaptiiviset komitealuokittimet voivat olla hyvin tehokkaita. Adaptiiviset komiteat voivat adaptoitua ilman yksityiskohtaista tietoa jäsenluokittimista. Adaptaatiota voidaan näin käyttää myös luokittelujärjestelmissä, jotka eivät ole itsessään sopivia adaptaatioon. Adaptaatioon sopimattomuus voi johtua esimerkiksi siitä, että luokittimen totetutusta ei voida muuttaa, tai siitä, että käytetään luokittelumenetelmää, joka ei sovellu jatkuvaan oppimiseen. Tämä väitöskirja käsittelee menetelmiä luokittimien adaptiiviseen yhdistämiseen käyttäen sovelluskohteena käsinkirjoitettujen merkkien on-line-tunnistusta. Keskeisin osa työtä esittelee uusia adaptiivisia luokittimien yhdistämismenetelmiä, joista kaksi huomattavinta ovat Dynamically Expanding Context (DEC) -komitea sekä Class-Confidence Critic Combining (CCCC) -komitea. Molemmat näistä ovat osoittautuneet kykeneviksi tehokkaaseen käyttäjä-adaptaatioon käsinkirjoitettujen merkkien on-line-tunnistuksessa. Erityisesti hyvin modulaarisella CCCC järjestelmällä on saatu hyviä tuloksia myös kaksinkertaisesti adaptiivisessa asetelmassa, jossa yhdistetään adaptiivisia jäsenluokittimia adaptiivisen komitean avulla. Väitöskirjan pääteeman tukena esitetään myös malli ja käytännön esimerkki siitä, miten käyttäjän toimista merkeille voidaan päätellä oikeat luokat. Merkkien todellisen luokan onnistunut päättely on elintärkeää tehokkaalle adaptaatiolle. Jotta adaptaatio voitaisiin suorittaa käyttäjälle läpinäkyvästi, merkkien todelliset luokat on kyettävä päättelemään käyttäjän toimista. Tällä tavalla käyttäjän ei tarvitse antaa suoraa palautetta tunnistustuloksen oikeellisuudesta. Työssä esitetään myös yleiskatsaus Teknillisen korkeakoulun Informaatiotekniikan laboratoriossa kehitettyyn adaptiiviseen käsinkirjoitettujen merkkien tunnistusjärjestelmään. Tähän järjestelmään perustuvia luokittimia on käytetty adaptiivisten komitealuokittimien kokeissa sekä jäsenluokittimina että vertailutasona. Lopuksi esitellään kaksi erillistä menetelmää komitealuokittimen tarkkuuden edelleen parantamiseksi. Näistä ensimmäinen on joukko menetelmiä komitealuokittimen rejektion (hylkäyksen) toteuttamiseksi. Toinen esiteltävä menetelmä on käyttää luokittimien erilaisuuden mittoja jäsenluokittimien valintaa varten. Ehdotetut uudet erilaisuusmitat perustuvat käsitteeseen, jota kutsumme virheiden erilaisuudeksi. Väitöskirjan aihe kattaa kolme hahmontunnistuksen tärkeää osa-aluetta: online-adaptaation, luokittimien yhdistämisen ja käytännön sovellusalana käsinkirjoitettujen merkkien tunnistuksen. Näistä kolmesta lähtökohdasta on kehitetty uudenlainen synteesi, joka esitetään johdantotekstissä sekä liitteenä olevissa julkaisuissa. Tämän väitöskirjan oleellisimmat kontribuutiot ovat siten: 1) uusien adaptiivisten komitealuokittimien esittely, 2) uudenlaisten menetelmien esittely luokittimien erilaisuuden mittaamiseksi, 3) joidenkin komitearejektiomenetelmien esittely, 4) pohdinnan ja erään toteutustavan esittely syötettyjen merkkien todellisen luokan päättelemiseksi käyttäjän toimista, sekä sivutuotteena 5) kattava yleiskatsaus CIS-HCR adaptiiviseen on-line käsinkirjoitettujen merkkien tunnistusjärjestelmään.reviewe

Advances in Character Recognition

This book presents advances in character recognition, and it consists of 12 chapters that cover wide range of topics on different aspects of character recognition. Hopefully, this book will serve as a reference source for academic research, for professionals working in the character recognition field and for all interested in the subject

Incorporation of relational information in feature representation for online handwriting recognition of Arabic characters

Interest in online handwriting recognition is increasing due to market demand for both improved performance and for extended supporting scripts for digital devices. Robust handwriting recognition of complex patterns of arbitrary scale, orientation and location is elusive to date because reaching a target recognition rate is not trivial for most of the applications in this field. Cursive scripts such as Arabic and Persian with complex character shapes make the recognition task even more difficult. Challenges in the discrimination capability of handwriting recognition systems depend heavily on the effectiveness of the features used to represent the data, the types of classifiers deployed and inclusive databases used for learning and recognition which cover variations in writing styles that introduce natural deformations in character shapes. This thesis aims to improve the efficiency of online recognition systems for Persian and Arabic characters by presenting new formal feature representations, algorithms, and a comprehensive database for online Arabic characters. The thesis contains the development of the first public collection of online handwritten data for the Arabic complete-shape character set. New ideas for incorporating relational information in a feature representation for this type of data are presented. The proposed techniques are computationally efficient and provide compact, yet representative, feature vectors. For the first time, a hybrid classifier is used for recognition of online Arabic complete-shape characters based on the idea of decomposing the input data into variables representing factors of the complete-shape characters and the combined use of the Bayesian network inference and support vector machines. We advocate the usefulness and practicality of the features and recognition methods with respect to the recognition of conventional metrics, such as accuracy and timeliness, as well as unconventional metrics. In particular, we evaluate a feature representation for different character class instances by its level of separation in the feature space. Our evaluation results for the available databases and for our own database of the characters' main shapes confirm a higher efficiency than previously reported techniques with respect to all metrics analyzed. For the complete-shape characters, our techniques resulted in a unique recognition efficiency comparable with the state-of-the-art results for main shape characters

Automated recognition of handwritten mathematics

Most software programs that deal with mathematical objects require input expressions to be linearized using somewhat awkward and unfamiliar string-based syntax. It is natural to desire a method for inputting mathematics using the same two-dimensional syntax employed with pen and paper, and the increasing prevalence of pen- and touch-based interfaces causes this topic to be of practical as well as theoretical interest. Accurately recognizing two-dimensional mathematical notation is a difficult problem that requires not only theoretical advancement over the traditional theories of string-based languages, but also careful consideration of runtime efficiency, data organization, and other practical concerns that arise during system construction. This thesis describes the math recognizer used in the MathBrush pen-math system. At a high level, the two-dimensional syntax of mathematical writing is formalized using a relational grammar. Rather than reporting a single recognition result, all recognizable interpretations of the input are simultaneously represented in a data structure called a parse forest. Individual interpretations may be extracted from the forest and reported one by one as the user requests them. These parsing techniques necessitate robust tree scoring functions, which themselves rely on several lower-level recognition processes for stroke grouping, symbol recognition, and spatial relation classification. The thesis covers the recognition, parsing, and scoring aspects of the MathBrush recognizer, as well as the algorithms and assumptions necessary to combine those systems and formalisms together into a useful and efficient software system. The effectiveness of the resulting system is measured through two accuracy evaluations. One evaluation uses a novel metric based on user effort, while the other replicates the evaluation process of an international accuracy competition. The evaluations show that not only is the performance of the MathBrush recognizer improving over time, but it is also significantly more accurate than other academic recognition systems

Text detection and recognition in natural images using computer vision techniques

El reconocimiento de texto en imágenes reales ha centrado la atención de muchos investigadores en todo el mundo en los últimos años. El motivo es el incremento de productos de bajo coste como teléfonos móviles o Tablet PCs que incorporan dispositivos de captura de imágenes y altas capacidades de procesamiento. Con estos antecedentes, esta tesis presenta un método robusto para detectar, localizar y reconocer texto horizontal en imágenes diurnas tomadas en escenarios reales. El reto es complejo dada la enorme variabilidad de los textos existentes y de las condiciones de captura en entornos reales. Inicialmente se presenta una revisión de los principales trabajos de los últimos años en el campo del reconocimiento de texto en imágenes naturales. Seguidamente, se lleva a cabo un estudio de las características más adecuadas para describir texto respecto de objetos no correspondientes con texto. Típicamente, un sistema de reconocimiento de texto en imágenes está formado por dos grandes etapas. La primera consiste en detectar si existe texto en la imagen y de localizarlo con la mayor precisión posible, minimizando la cantidad de texto no detectado así como el número de falsos positivos. La segunda etapa consiste en reconocer el texto extraído. El método de detección aquí propuesto está basado en análisis de componentes conexos tras aplicar una segmentación que combina un método global como MSER con un método local, de forma que se mejoran las propuestas del estado del arte al segmentar texto incluso en situaciones complejas como imágenes borrosas o de muy baja resolución. El proceso de análisis de los componentes conexos extraídos se optimiza mediante algoritmos genéticos. Al contrario que otros sistemas, nosotros proponemos un método recursivo que permite restaurar aquellos objetos correspondientes con texto y que inicialmente son erróneamente descartados. De esta forma, se consigue mejorar en gran medida la fiabilidad de la detección. Aunque el método propuesto está basado en análisis de componentes conexos, en esta tesis se utiliza también la idea de los métodos basados en texturas para validar las áreas de texto detectadas. Por otro lado, nuestro método para reconocer texto se basa en identificar cada caracter y aplicar posteriormente un modelo de lenguaje para corregir las palabras mal reconocidas, al restringir la solución a un diccionario que contiene el conjunto de posibles términos. Se propone una nueva característica para reconocer los caracteres, a la que hemos dado el nombre de Direction Histogram (DH). Se basa en calcular el histograma de las direcciones del gradiente en los pixeles de borde. Esta característica se compara con otras del estado del arte y los resultados experimentales obtenidos sobre una base de datos compleja muestran que nuestra propuesta es adecuada ya que supera otros trabajos del estado del arte. Presentamos también un método de clasificación borrosa de letras basado en KNN, el cual permite separar caracteres erróneamente conectados durante la etapa de segmentación. El método de reconocimiento de texto propuesto no es solo capaz de reconocer palabras, sino también números y signos de puntuación. El reconocimiento de palabras se lleva a cabo mediante un modelo de lenguaje basado en inferencia probabilística y el British National Corpus, un completo diccionario del inglés británico moderno, si bien el algoritmo puede ser fácilmente adaptado para ser usado con cualquier otro diccionario. El modelo de lenguaje utiliza una modificación del algoritmo forward usando en Modelos Ocultos de Markov. Para comprobar el rendimiento del sistema propuesto, se han obtenido resultados experimentales con distintas bases de datos, las cuales incluyen imágenes en diferentes escenarios y situaciones. Estas bases de datos han sido usadas como banco de pruebas en la última década por la mayoría de investigadores en el área de reconocimiento de texto en imágenes naturales. Los resultados muestran que el sistema propuesto logra un rendimiento similar al del estado del arte en términos de localización, mientras que lo supera en términos de reconocimiento. Con objeto de mostrar la aplicabilidad del método propuesto en esta tesis, se presenta también un sistema de detección y reconocimiento de la información contenida en paneles de tráfico basado en el algoritmo desarrollado. El objetivo de esta aplicación es la creación automática de inventarios de paneles de tráfico de países o regiones que faciliten el mantenimiento de la señalización vertical de las carreteras, usando imágenes disponibles en el servicio Street View de Google. Se ha creado una base de datos para esta aplicación. Proponemos modelar los paneles de tráfico usando apariencia visual en lugar de las clásicas soluciones que utilizan bordes o características geométricas, con objeto de detectar aquellas imágenes en las que existen paneles de tráfico. Los resultados experimentales muestran la viabilidad del sistema propuesto