In this paper we describe a new system for storing annotated images in a large database and querying by means of a dynamical retrieval of images through use of metadata. It is based on a three-tier architecture suitable for building a common gateway for accessing heterogeneous data. Based on XML schema of documents, the extraction of metadata is used for successive querying. We give an example on a database of astronomical and geographical images, but the method is quite general and can be applied to more general case of large heterogeneous databases.
In this paper we present a novel digital watermarking technique for still image authentication. A model of the Human Visual System is exploited not only to enhance the visual quality of the watermarked images, but also to enhance the receiver’s probability of extracting the watermark correctly. Our goal is to jointly optimize rate, robustness and visibility, so that detailed features can be embedded, content-preserving manipulations are tolerated and the authenticated image is not distorted too severely by the embedding process. The algorithm performance has been assessed through numerical simulations and comparisons with the current state of the art. Results prove significant improvements in robustness against perceptually lossless modifications (such as mild JPEG and JPEG2000 compression).
In this work we study a combination between wavelet transform and a model of the human visual system both from the mathematical and the computational point of view. We will combine the two procedures in such a way that the computational complexity of the whole procedure is reduced for the maximum possible amount. The gaol is to improve the quality compression, by modelling the human visual system in the compression-decompression tasks. As a result, new filters for image compression are provided for any given multiresolution analysis, independently of the coding method adopted. The proposed algorithm has been applied to grey level images and compared to more traditional approaches which do not comprehend a modelization of the human visual system.
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