Abstract
The objective of this thesis is to acquire abstract image features through statistical modelling in the wavelet domain and then based on the extracted image features, develop an effective content-based image retreival (CBIR) system and a fragile watermarking scheme. In this thesis, we first present a statistical modelling of images in the wavelet domain through a Gaussian mixture model (GMM) and a generalized Gaussian mixture model (GGMM). An Expectation Maximization (EM) algorithm is developed to help estimate the model parameters. A novel similarity measure based on the Kullback-Leibler divergence is also developed to calculate the distance of two distinct model distributions. We then apply the statistical modelling to two application areas: image retrieval and fragile watermarking. In image retrieval, the model parameters are employed as image features to compose the indexing feature space, while the feature distance of two compared images is computed using the novel similarity measure. The new image retrieval method has a better retrieval performance than most conventional methods. In fragile watermarking, the model parameters are utilized for the watermark embedding. The new watermarking scheme achieves a virtually imperceptible embedding of watermarks because it modifies only a few image data and embeds watermarks at image texture edges. A multiscale embedding of fragile watermarks is given to enhance the embeddability rate and on the other hand, to constitute a semi-fragile approach.
Highlights
1.1 M otivation and O b jectivesMany image applications require an accurate modelling of images to have a better under standing and utilization of image contents
In C hapter 3, we develop a statistical modelling of images in the wavelet domain through Gaussian mixture model (GMM) and generalized Gaussian mixture model (GGMM)
Many image applications are based on the image characteristics obtained from image mod elling
Summary
Many image applications require an accurate modelling of images to have a better under standing and utilization of image contents. Our interest lies in the derivation of some new feature extraction methods based on the developed statistical modelling to have a compact indexing feature space. It is desired th a t the 2 extracted image features can reflect some characteristics of human perception and have a sound image retrieval performance. Most traditional fragile watermarking methods inevitably need to modify a large amount of image data for watermark embedding in order to protect the whole image area. We aim at developing a new fragile watermarking method th at modifies a few image data for watermark embedding, while keeping sensitive to any image tampering.
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