Pagrindinis darbo tikslas yra pritaikant dirbtinio intelekto algoritmus sukurti ranka rašyto teksto atpažinimo įrankį. Siekiant šio tikslo buvo apžvelgti dirbtinio intelekto atpažinimo metodai, atlikta teksto atpažinimo algoritmų analizė. Remiantis analizės rezultatais, sukurta ranka rašyto teksto atpažinimo programa, kurioje teksto segmentavimo operacija atliekama „lašelio aptikimo“ algoritmu. Teksto atpažinimo operacijai atlikti naudojamas bitų masyvų analizės algoritmas. / The aim of this work is to create an application for handwritten text recognition using artificial intelligence algorithms. For this purpose a number of recognition methods based on artificial intelligence were reviewed. Based on the review information an application was created for the purpose of recognizing handwritten text. The text segmentation was implemented using a blob detection algorithm. Text recognition was performed using bit array analysis algorithm. During the implementation and testing stage the main problem areas of such application were identified.

Made available in DSpace on 2014-06-12T15:58:13Z (GMT). No. of bitstreams: 2 arquivo3310_1.pdf: 8155353 bytes, checksum: 2f4dcd5adb2b0b1a23c40bf343b36b34 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Faculdade de Amparo à Ciência e Tecnologia do Estado de Pernambuco / Ensemble of Classifiers (EoC) é uma nova alternative para alcançar altas taxas de reconhecimento em sistemas de reconhecimento de padrões. O uso de ensemble é motivado pelo fato de que classificadores diferentes conseguem reconhecer padrões diferentes, portanto, eles são complementares. Neste trabalho, as metodologias de EoC são exploradas com o intuito de melhorar a taxa de reconhecimento em diferentes problemas. Primeiramente o problema do reconhecimento de caracteres é abordado. Este trabalho propõe uma nova metodologia que utiliza múltiplas técnicas de extração de características, cada uma utilizando uma abordagem diferente (bordas, gradiente, projeções). Cada técnica é vista como um sub-problema possuindo seu próprio classificador. As saídas deste classificador são utilizadas como entrada para um novo classificador que é treinado para fazer a combinação (fusão) dos resultados. Experimentos realizados demonstram que a proposta apresentou o melhor resultado na literatura pra problemas tanto de reconhecimento de dígitos como para o reconhecimento de letras. A segunda parte da dissertação trata da seleção dinâmica de classificadores (DCS). Esta estratégia é motivada pelo fato que nem todo classificador pertencente ao ensemble é um especialista para todo padrão de teste. A seleção dinâmica tenta selecionar apenas os classificadores que possuem melhor desempenho em uma dada região próxima ao padrão de entrada para classificar o padrão de entrada. É feito um estudo sobre o comportamento das técnicas de DCS demonstrando que elas são limitadas pela qualidade da região em volta do padrão de entrada. Baseada nesta análise, duas técnicas para seleção dinâmica de classificadores são propostas. A primeira utiliza filtros para redução de ruídos próximos do padrão de testes. A segunda é uma nova proposta que visa extrair diferentes tipos de informação, a partir do comportamento dos classificadores, e utiliza estas informações para decidir se um classificador deve ser selecionado ou não. Experimentos conduzidos em diversos problemas de reconhecimento de padrões demonstram que as técnicas propostas apresentam um aumento de performance significante

The handwritten recognition system is a process of learning a pattern from a given image of text. The recognition process usually combines a computer vision task with sequence learning techniques. Transcribing texts from the scanned image remains a challenging problem, especially when the documents are highly degraded, or have excessive dusty noises. Nowadays, there are several handwritten recognition systems both commercially and in free versions, especially for Latin based languages. However, there is no prior study that has been built for Ge’ez handwritten ancient manuscript documents. In contrast, the language has many mysteries of the past, in human history of science, architecture, medicine and astronomy. In this thesis, we present two separate recognition systems. (1) A character-level recognition system which combines computer vision for character segmentation from ancient books and a vanilla Convolutional Neural Network (CNN) to recognize characters. (2) An end- to- end segmentation free handwritten recognition system using CNN, Multi-Dimensional Recurrent Neural Network (MDRNN) with Connectionist Temporal Classification (CTC) for the Ethiopic (Ge’ez) manuscript documents. The proposed character label recognition model outperforms 97.78% accuracy. In contrast, the second model provides an encouraging result which indicates to further study the language properties for better recognition of all the ancient books. / Det handskrivna igenkännings systemet är en process för att lära sig ett mönster från en viss bild av text. Erkännande Processen kombinerar vanligtvis en datorvisionsuppgift med sekvens inlärningstekniker. Transkribering av texter från den skannade bilden är fortfarande ett utmanande problem, särskilt när dokumenten är mycket försämrad eller har för omåttlig dammiga buller. Nuförtiden finns det flera handskrivna igenkänningar system både kommersiellt och i gratisversionen, särskilt för latin baserade språk. Det finns dock ingen tidigare studie som har byggts för Ge’ez handskrivna gamla manuskript dokument. I motsats till detta språk har många mysterier från det förflutna, i vetenskapens mänskliga historia, arkitektur, medicin och astronomi. I denna avhandling presenterar vi två separata igenkänningssystem. (1) Ett karaktärs nivå igenkänningssystem som kombinerar bildigenkänning för karaktär segmentering från forntida böcker och ett vanilj Convolutional Neural Network (CNN) för att erkänna karaktärer. (2) Ett änd-till-slut-segmentering fritt handskrivet igenkänningssystem som använder CNN, Multi-Dimensional Recurrent Neural Network (MDRNN) med Connectionist Temporal Classification (CTC) för etiopiska (Ge’ez) manuskript dokument. Den föreslagna karaktär igenkännings modellen överträffar 97,78% noggrannhet. Däremot ger den andra modellen ett uppmuntrande resultat som indikerar att ytterligare studera språk egenskaperna för bättre igenkänning av alla antika böcker.

In this thesis, we address some of the challenges involved in developing a robust writer-independent, lexicon-free system to recognize online Tamil words. Tamil, being a Dravidian language, is morphologically rich and also agglutinative and thus does not have a finite lexicon. For example, a single verb root can easily lead to hundreds of words after morphological changes and agglutination. Further, adoption of a lexicon-free recognition approach can be applied to form-filling applications, wherein the lexicon can become cumbersome (if not impossible) to capture all possible names. Under such circumstances, one must necessarily explore the possibility of segmenting a Tamil word to its individual symbols. Modern day Tamil alphabet comprises 23 consonants and 11 vowels forming a total combination of 313 characters/aksharas. A minimal set of 155 distinct symbols have been derived to recognize these characters. A corpus of isolated Tamil symbols (IWFHR database) is used for deriving the various statistics proposed in this work. To address the challenges of segmentation and recognition (the primary focus of the thesis), Tamil words are collected using a custom application running on a tablet PC. A set of 10000 words (comprising 53246 symbols) have been collected from high school students and used for the experiments in this thesis. We refer to this database as the ‘MILE word database’. In the first part of the work, a feedback based word segmentation mechanism has been proposed. Initially, the Tamil word is segmented based on a bounding box overlap criterion. This dominant overlap criterion segmentation (DOCS) generates a set of candidate stroke groups. Thereafter, attention is paid to certain attributes from the resulting stroke groups for detecting any possible splits or under-segmentations. By relying on feedbacks provided by a priori knowledge of attributes such as number of dominant points and inter-stroke displacements the recognition label and likelihood of the primary SVM classifier linguistic knowledge on the detected stroke groups, a decision is taken to correct it or not. Accordingly, we call the proposed segmentation as ‘attention feedback segmentation’ (AFS). Across the words in the MILE word database, a segmentation rate of 99.7% is achieved at symbol level with AFS. The high segmentation rate (with feedback) in turn improves the symbol recognition rate of the primary SVM classifier from 83.9% (with DOCS alone) to 88.4%. For addressing the problem of segmentation, the SVM classifier fed with the x-y trace of the normalized and resampled online stroke groups is quite effective. However, the performance of the classifier is not robust to effectively distinguish between many sets of similar looking symbols. In order to improve the symbol recognition performance, we explore two approaches, namely reevaluation strategies and language models. The reevaluation techniques, in particular, resolve the ambiguities in base consonants, pure consonants and vowel modifiers to a considerable extent. For the frequently confused sets (derived from the confusion matrix), a dynamic time warping (DTW) approach is proposed to automatically extract their discriminative regions. Dedicated to each confusion set, novel localized cues are derived from the discriminative region for their disambiguation. The proposed features are quite promising in improving the symbol recognition performance of the confusion sets. Comparative experimental analysis of these features with x-y coordinates are performed for judging their discriminative power. The resolving of confusions is accomplished with expert networks, comprising discriminative region extractor, feature extractor and SVM. The proposed techniques improve the symbol recognition rate by 3.5% (from 88.4% to 91.9%) on the MILE word database over the primary SVM classifier. In the final part of the thesis, we integrate linguistic knowledge (derived from a text corpus) in the primary recognition system. The biclass, bigram and unigram language models at symbol level are compared in terms of recognition performance. Amongst the three models, the bigram model is shown to give the highest recognition accuracy. A class reduction approach for recognition is adopted by incorporating the language bigram model at the akshara level. Lastly, a judicious combination of reevaluation techniques with language models is proposed in this work. Overall, an improvement of up to 4.7% (from 88.4% to 93.1%) in symbol level accuracy is achieved. The writer-independent and lexicon-free segmentation-recognition approach developed in this thesis for online handwritten Tamil word recognition is promising. The best performance of 93.1% (achieved at symbol level) is comparable to the highest reported accuracy in the literature for Tamil symbols. However, the latter one is on a database of isolated symbols (IWFHR competition test dataset), whereas our accuracy is on a database of 10000 words and thus, a product of segmentation and classifier accuracies. The recognition performance obtained may be enhanced further by experimenting on and choosing the best set of features and classifiers. Also, the word recognition performance can be very significantly improved by using a lexicon. However, these are not the issues addressed by the thesis. We hope that the lexicon-free experiments reported in this work will serve as a benchmark for future efforts.