With the advent research of Document Image Analysis and Recognition (DIAR), an important line of research is explored on indexing and retrieval of graphics rich docu- ments. It aims at nding relevant documents relying on segmentation and recognition of text and graphics components underlying in non-standard layout where commercial OCRs can not be applied due to complexity. This thesis is focused towards text infor- mation extraction approaches in graphical documents and retrieval of such documents using text information. Automatic text recognition in graphical documents (map, engineering drawing, etc.) involves many challenges because text characters are usually printed in multi- oriented and multi-scale way along with di erent graphical objects. Text characters are used to annotate the graphical curve lines and hence, many times they follow curvi-linear paths too. For OCR of such documents, individual text lines and their corresponding words/characters need to be extracted. For recognition of multi-font, multi-scale and multi-oriented characters, we have proposed a feature descriptor for character shape using angular information from con- tour pixels to take care of the invariance nature. To improve the e ciency of OCR, an approach towards the segmentation of multi-oriented touching strings into individual characters is also discussed. Convex hull based background information is used to segment a touching string into possible primitive segments and later these primitive segments are merged to get optimum segmentation using dynamic programming. To overcome the touching/overlapping problem of text with graphical lines, a character spotting approach using SIFT and skeleton information is included. Afterwards, we propose a novel method to extract individual curvi-linear text lines using the fore- ground and background information of the characters of the text and a water reservoir concept is used to utilize the background information. We have also formulated the methodologies for graphical document retrieval ap- plications using query words and seals. The retrieval approaches are performed using recognition results of individual components in the document. Given a query text, the system extracts positional knowledge from the query word and uses the same to generate hypothetical locations in the document. Indexing of documents is also per- formed based on automatic detection of seals from documents containing cluttered background. A seal is characterized by scale and rotation invariant spatial feature descriptors computed from labelled text characters and a concept based on the Generalized Hough Transform is used to locate the seal in documents. Keywords: Document Image Analysis, Graphics Recognition, Dynamic Pro- gramming, Generalized Hough Transform, Character Recognition, Touching Charac- ter Segmentation, Text/Graphics Separation, Curve-Line Separation, Word Retrieval, Seal Detection and Recognition.

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Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-03-15T14:22:48Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese - Alberto Lopes_FINAL.pdf: 3638051 bytes, checksum: eaabca9285409b7fd175305c73677557 (MD5) / Made available in DSpace on 2016-03-15T14:22:48Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese - Alberto Lopes_FINAL.pdf: 3638051 bytes, checksum: eaabca9285409b7fd175305c73677557 (MD5) Previous issue date: 2015-02-26 / Dentre os problemas e desafios que permeiam o processo de digitalização de documentos e todos os passos subsequentes até a transposição da informação para o meio digital, dois pontos específicos são focados: o texto partido ou degradado e texto escrito em tamanha proximidade que geram sobreposições dos traços. Assim, métodos para solucionar tais problemas, foram pesquisados e desenvolvidos. Baseamos nossa abordagem na emulação de forças físicas de inércia e centrípeta pois entendemos que estas podem ser bem utilizadas para o processamento de imagens de caracteres manuscritos. Para o problema de dígitos partidos, foi desenvolvida uma solução para a restauração de dígitos isolados quebrados e de cadeias de dígitos quebrados através da emulação das forças centrípeta e de inércia. Esta solução tem como princípio gerar uma reconstrução da quebra de modo que se assemelhe à escrita do dígito em questão. Também é abordado a sobreposição de pares de dígitos, problema para o qual foi proposta uma solução de segmentação. Esta solução de segmentação se baseia no conceito de uma bola deformável que tem seus movimentos regidos pela emulação da força de inércia e pela deformação que lhe é permitida receber. Ainda, para desenvolvimento e experimentação dos métodos, foram formadas bases de imagens pertinentes a cada aplicação. Os resultados obtidos mostram desempenhos promissores. Ao aplicar a reconstrução, obtivemos um ganho de aproximadamente seis pontos percentuais em taxa de reconhecimento em relação ao reconhecimento dos dígitos partidos. Já a segmentação provou que supera outros dois métodos de segmentação quando aplicamos o reconhecimento aos dígitos segmentados. Também deve-se ressaltar a questão do custo computacional, especificamente a solução voltada para a segmentação de dígitos sobrepostos, onde seu custo se apresenta mais baixo em relação aos métodos similares pesquisados e testados. Assim, mostramos que os métodos propostos atingem seus objetivos, aliando bons desempenhos com custos computacionais baixos. / Among the problems and challenges that surround the process of document digitization and all subsequent steps until the conversion of the information to a digital medium, two specific steps are focused: broken text and text written in such proximity that cause overlapping of strokes. Methods to solve these problems were researched and developed. We base our approach on the emulation of physical forces of inertia and centripetal force, since it is our understanding that the emulation of such forces can be used for the processing of images of handwritten characters and digits. For the problem of broken digits, a solution for the restoration of isolated broken digits and chains of broken digits through the emulations of inertia and centripetal force was developed. This solution has as principle to generate a reconstruction of the break in such a way that it resembles closely the writing style of the digit in question. We also tackle overlapping pairs of digits, problem for which we propose a segmentation solution. This segmentation is based on the concept of a deformable ball that has its movements governed by the emulation of inertia and the degree of deformation the ball is allowed to have. For development and experimentation of the created methods, image databases pertinent to each application were formed. The obtained results show promising performance. When applying the reconstruction, we obtained a gain of approximately six percentage points in recognition rates when compared to rates obtained for broken digits. In regards to segmentation, it proved to outperform two other methods when recognition is applied to the output segmented digits. The computational cost of the methods should also be pointed out, specifically regarding the solution created for the segmentation of overlapped digits, which is lower when compared to other similar methods that were researched and tested. Therefore, we show that the proposed methods reach their goals, coupling performance with low computational costs.