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| Author(s): |
Otávio Augusto Bizetto Penatti
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Computação |
| Defense date: | 2009-03-13 |
| Examining board members: |
Ricardo da Silva Torres;
João Marcos Bastos Cavalcanti;
Alexandre Xavier Falcão
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| Advisor: | Ricardo da Silva Torres |
| Abstract | |
The growth in size of image collections and the worldwide availability of these collections has increased the demand for image retrieval systems. A promising approach to address this demand is to retrieve images based on image content (Content-Based Image Retrieval). This approach considers the image visual properties, like color, texture and shape of objects, for indexing and retrieval. The main component of a content-based image retrieval system is the image descriptor. The image descriptor is responsible for encoding image properties into feature vectors. Given two feature vectors, the descriptor compares them and computes a distance value. This value quantifies the difference between the images represented by their vectors. In a content-based image retrieval system, these distance values are used to rank database images with respect to their distance to a given query image. This dissertation presents a comparative study of image descriptors considering the Web as the environment of use. This environment presents a huge amount of images with heterogeneous content. The comparative study was conducted by taking into account two approaches. The first approach considers the asymptotic complexity of feature vectors extraction algorithms and distance functions, the size of the feature vectors generated by the descriptors and the environment where each descriptor was validated. The second approach compares the descriptors in practical experiments using four different image databases. The evaluation considers the time required for features extraction, the time for computing distance values, the storage requirements and the effectiveness of each descriptor. Color, texture, and shape descriptors were compared. The experiments were performed with each kind of descriptor independently and, based on these results, a set of descriptors was evaluated in an image database containing more than 230 thousand heterogeneous images, reflecting the content existent in the Web. The evaluation of descriptors effectiveness in the heterogeneous database was made by experiments using real users. This dissertation also presents a tool for executing experiments aiming to evaluate image descriptors. (AU) | |