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New contributions on image fusion and compression based on space-frequency representations

Otros títulosNuevas contribuciones en fusión y compresión de imágenes basadas en representaciones espacio-frecuenciales
AutorRedondo, Rafael
DirectorCristóbal Pérez, Gabriel; Ledesma, María Jesús
Palabras claveImage analysis
Wigner Distribution
Gabor representation
Chain code
Fecha de publicación20-abr-2007
ResumenJoint representations have experimented a significant height in signal processing during the last decades, to such an extent that there is no topic they have not been utilized for. Within a sea of joint representations existent in the literature, one of them concerns the present work: the log-Gabor multiresolution transform proposed in [70, 68]. Its low spectral overlapping, high selectivity in orientation and scalability, shift-invariance, self-invertibility and complex definition confers efficiency, versatility and robustness against noise and a low presence of artifacts. Further on, the tight similarity of overcomplete log-Gabor filters to the cortical area V1, together with the modeling of inhibitory/ facilitatory neuronal behaviors and sparse coding algorithms allow to achieve an approximation of the image based on the extraction of those salient features normally coincident with contours. This type of image representation based on multiscale contours traces new routes to solve image processing tasks, in particular in the areas of image compression and fusion. A recent compression paradigm postulates higher efficiency from coding separately features present in images, such as luminance, contours or textures [19, 145, 240]. Following that paradigm, in this thesis a new compression method is proposed based on coding those multiscale contours extracted from the sparse log-Gabor transformation. In account of the nature of such features, a chain coding algorithm has been specially tailored to the stochastic and morphological peculiarities of multiscale contours. Thus, different predictive techniques as well as preffix and arithmetic coding have been combined according to each alphabet. Moreover, the proposed algorithm offers a complete compression scheme including low-pass coding as well as header bitstream allocation. Such coding rest on a model of the primary visual cortex in order to mitigate typical compression distortions usually produced by compression standards such as JPEG and JPEG2000. Multiresolution decompositions have proven their superiority against other traditional image fusion techniques. Nevertheless it does not exist any evident hegemony, often due to the lack of a reference image. In this thesis, several types of wavelets were compared to log-Gabor filters, which succeeded remarkably, but they were never used before on account of its traditional lack of exact reconstruction. Further, a general algorithm for multiresolution schemes named multisize windows is proposed. It adapts the size of the averaging window according to the local features in the image and exploits the advantages of both small, i.e. precise, and big, i.e. robust, windows showing significant reduction on errors in decision maps in contrast to traditional fixed window approaches. Finally, a novel contour-based fusion method is also proposed by integrating the multiscale contours to multiresolution fusion. This feature-based algorithm reduces the sensitivity to noise, blurring effects and misregistration artifacts.
DescripciónTesis doctoral de la Escuela Técnica Superior de Ingenieros de Telecomunicación de la Universidad Politécnica de Madrid (ETSIT-UPM) y del Instituto de Óptica "Daza de Valdés" del Consejo Superior de Investigaciones Científicas (IO-CSIC).-- 181 págs.
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