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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Correção do efeito Show-Through baseada em técnicas de separação cega de fontes

Castillo, Renato Martín De La Rosa January 2015 (has links)
Orientador: Prof. Dr. Ricardo Suyama / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia da Informação, 2015. / No processo de digitalização de documentos impressos ou manuscritos que apresentam informação em ambos os lados da folha (frente e verso), é comum encontrar uma distorção na imagem digitalizada conhecida como Efeito Show-Through, na qual a imagem digitalizada de um dos lados do documento sofre a interferência da imagem presente no outro lado da folha. O problema de remoção dessa interferência pode ser visto como uma instância do problema geral de Separação Cega de Fontes (BSS ¿ Blind Source Separation), para o qual diferentes técnicas foram propostas, baseadas nas características das fontes e no processo de mistura. No presente trabalho avaliamos diferentes técnicas para a solução do problema de Show-through que utilizam os conceitos relacionados ao problema de Separação Cega de Fontes, buscando identificar vantagens e desvantagens dos diferentes métodos. As técnicas avaliadas, baseadas em três diferentes abordagens em termos do critério de adaptação dos parâmetros, foram testadas com diferentes tipos de documentos (textos antigos ,manuscritos,jornal,etc) digitalizados, considerando misturas sintéticas e misturas reais, obtidas com a digitalização de documentos impressos. Os resultados obtidos revelam pontos fortes e fracos das técnicas avaliadas, e poderão servir como referência para o desenvolvimento de novas técnicas para a correção do efeito Show-Through. / In the digitalization process of printed documents or manuscripts that contain information on both through sides of the paper (front and back), it is common to observe the so-called Show-Thorugh Effet, in which the image in the back of the document interferes in the digitized image of the front side. Removing this kind of interference can be seen as an instance of the general Blind Source Separation Problem (BSS), for which several different techniques have been proposed in the literature, considering specific characteristics of the sources and of the mixing process. The objective of the present work is to evaluate different methods for the mitigation of the Show-Through effect, based in concepts related to the BSS problem. The evaluated tools, based on three different approaches for parameter adaptation, were tested with different kinds of documents (old texts, manuscripts, newspaper), considering synthetic and real mixtures. The results reveal strong and weak points of the studied methods, which can serve as a valuable reference in the development of new techniques for the Show-Through effect mitigation.
2

Evaluating Methods for Show-through or Bleed-through Cancellation

Martin Welin, Erik, Åström, Andreas January 2021 (has links)
The theme of this paper is show-through andbleed-through cancellation of degraded images or manuscripts.Show-through and bleed-through is when the reverse side of amanuscripts shows/bleeds through to the front side. This canseverely impact readability. Four different cancellation algorithmswas chosen for evaluation. The methods considered areThresholding, ICA and two other methods, herewithin referredto as ’Dubojs’ and ’ISJ4’. ICA is a blind source separationmethod. Dubojs is a more sophisticated thresholding method,while ISJ4 uses statistical methods for estimating parameters ofa show-through model. In this paper, the different algorithms areevaluated on different types of common text degradations. Theauthors found that the most useful methods were ISJ4, Dubojsand ICA, with ISJ4 being the most flexible. Thresholding wasfound to be too simple. Dubojs needs improved segmentationto work properly, but was useful in a particular case of strongbleed-through. ICA was easy to use, but required linear mixturesto work properly. / Temat för detta arbete är borttagning av’show-through’ och ’bleed-through’ som påverkat läsbarhetenhos skannade, eller handskrivna dokument negativt. Dessafenomen uppstår på dubbelsidiga dokument och leder till attdelar av baksidan dyker upp på framsidan och vice versa.Fyra olika algoritmer som tar bort de oönskade bidragen harutvärderats. Dessa är Thresholding, ICA och två andra metodersom kommit att kallas ’Dubojs’ och ’ISJ4’. Dubojs är enmer sofistikerad Thresholding-algoritm medan ISJ4 använderstatistiksa metoder för att skatta paremterar i en show-throughmodell.Algoritmerna testades och utvärderades på dokumentsom påverkats av show/bleed-through i olika utsträckning.Författarna fann att de mest användbara metoderna var ISJ4,Dubojs och ICA, där ISJ4 var mest flexibel. Thresholding varför simpel för att vara riktigt användbar. Dubojs skulle behövaförbättrad klassificering, men var användbar i ett speciellt fallav bleed-through. ICA var lätt att använda, men krävde linjärablandningar för att fungera på ett önskvärt sätt. / Kandidatexjobb i elektroteknik 2021, KTH, Stockholm

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