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I-Search Project Project Members
IntroductionVisual information retrieval is a new subject of research in information technology. Its purpose is to retrieval from a database, images or image sequences that are relevant to a query. It is an extension of traditional information retrieval designed to include visual media. The variety of knowledge required in visual information retrieval is large. Different research fields, which have involved separately, provide valuable contributions to this new research subject. Information retrieval, visual data modeling and representation, image/video analysis and processing, pattern recognition and computer vision, multimedia database organization, multidimensional indexing, psychological modeling of user behavior, man-machine interaction and data visualization, are the most important research fields that contribute to visual information retrieval. New-generation visual information retrieval systems support full retrieval by visual content. Access to visual information is not only performed at a conceptual level, using keywords as in the textual domain, but also at a perceptual level, using objective measurements of visual content and appropriate similarity models. The contents include:
In typical content-based image retrieval systems (Figure 1), the visual
contents of the images in the database are extracted and described by
multi-dimensional feature vectors. The
Following are the problems to be solved in a CBIR system:
MethodsSIMBAWe have developed a demo image retrieval system-SIMBA(Search IMages By Appearance). Our approach is based on invariant features, i.e. features that do not vary if the image is transformed by some transformation group (we will consider translation and rotation here). Schulz-Mirbach introduced an algorithm for the construction of invariant features [Schulz-Mirbach:1995] which is very suitable because of its robustness to slight topological deformations and even to independent motion of objects within the image. The major advantage is that it does not require the extraction of objects (segmentation), or distinct points (key-points) from the image, but can be applied directly to the original image data. However, in order to improve the algorithm's robustness in an image retrieval application - especially for supporting partial matches - we had to modify it, so that more local information is preserved in the final features. Thus we constructed feature histograms [Siggelkow, Burkhardt:1998], which are very similar to the well known color histograms but consider features drawn from a local neighborhood of each pixel instead of just using the color value of each pixel only. Thus we incorporate also textural information. Recently the method was further enhanced by a fast estimation of the features instead of a tedious calculation. Thus the extracted features will have a small error which, however, can be well estimated [Siggelkow, Schael:1999]. Enhancement during I-SearchThe I-Search project aims at the construction of a content-based image retrieval system, which is successfully implemented. Our contribution is the development and enhancement of image representation and image similarity algorithms. We developed a broad band feature extraction library capable to help solving content-based image queries. Hence, we can significantly improve the quality of our chair's local invariant texture features [4][7]. Further, we could develop a new method, based on inter-structural information [6][10]. A further module of our algorithmic palette specifies image features based on the JPEG2000 image-standard [9]. Moreover we implemented a feature selection method, which finds 'the best' features out of many for an arbitrary image query, leading to better results [8]. The choice of different feature methods is concluded by an inter-active algorithm, which is known in the literature as Relevance Feedback. Relevance Feedback enables through a distinct selection of images by the user an iterative enhancement of the image retrieval results. Where, the selected images should be similar to the query image. The inter-active enhancement of the results is obtained by a Support Vector Machine, which learns the user's image selection [5]. Thus, one can improve the original results by several iterations. In the scope of I-Search we develop several algorithms for content-based image retrieval tasks. The methods might be of help for different image query problems. We would like to stress, that there is no single best algorithm, it is much more the smart choice or proper combination of different methods, leading to a satisfactory result.References
Links of related projects
Publications
Demos and ToolsSIMBA (Search IMages By Appearance)This page is maintained by Lin Mei(mei@informatik.uni-freiburg.de) & Gerd Brunner(gbrunner@informatik.uni-freiburg.de) |