Dimosthenis Karatzas



Text Segmentation in Web Images Using Colour Perception and Topological Features

D. Karatzas

PhD Thesis, University of Liverpool, 2003


The research presented in this thesis addresses the problem of Text Segmentation in Web images. Text is routinely created in image form (headers, banners etc.) on Web pages, as an attempt to overcome the stylistic limitations of HTML. This text however, has a potentially high semantic value in terms of indexing and searching for the corresponding Web pages. As current search engine technology does not allow for text extraction and recognition in images, the text in image form is ignored. Moreover, it is desirable to obtain a uniform representation of all visible text of a Web page (for applications such as voice browsing or automated content analysis). This thesis presents two methods for text segmentation in Web images using colour perception and topological features.

The nature of Web images and the implicit problems to text segmentation are described, and a study is performed to assess the magnitude of the problem and establish the need for automated text segmentation methods.

Two segmentation methods are subsequently presented: the Split-and-Merge segmentation method and the Fuzzy segmentation method. Although approached in a distinctly different way in each method, the safe assumption that a human being should be able to read the text in any given Web Image is the foundation of both methodsí reasoning. This anthropocentric character of the methods along with the use of topological features of connected components, comprise the underlying working principles of the methods.

An approach for classifying the connected components resulting from the segmentation methods as either characters or parts of the background is also presented.

Full Thesis



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