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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Asservissement visuel direct utilisant les décompositions en shearlets et en ondelettes de l'image / Direct visual servoingusing shearlet and wavelet transforms of the image

Duflot, Lesley-Ann 13 July 2018 (has links)
L'asservissement visuel est un procédé consistant à utiliser l'information visuelle obtenue par un capteur afin de commander un système robotique. Ces informations, appelées primitives visuelles peuvent être d'ordre 2D ou 3D. Le travail présenté ici porte sur une nouvelle approche 2D utilisant des primitives directes : les décompositions de l'image en ondelettes ou en shearlets. Ces représentations présentent en effet l'avantage de décrire l'image sous différentes formes, mettant l'accent soit sur les basses fréquences de l'image, soit sur les hautes fréquences selon plusieurs directions. Les zones de l'image contenant beaucoup d'information, comme les contours ou les points singuliers, possèdent alors de forts coefficients dans la transformée en ondelettes ou en shearlets de l'image, tandis que les zones uniformes possèdent des coefficients proches de zéro. Les travaux de cette thèse montrent la précision et la robustesse de l'approche utilisant la décomposition en shearlets dans le cadre de l'imagerie échographique. Néanmoins, sa contribution majeure est l'élaboration d'une commande permettant d'utiliser au choix les ondelettes ou les shearlets ainsi que la validation de cette méthode sur caméra monoculaire et sur capteur de type tomographie par cohérence optique dans différentes conditions d'utilisation. Cette méthode présente des performances significatives en termes de précision et de robustesse et ouvre la porte vers une utilisation couplée de l'asservissement visuel et de l'acquisition comprimée. / A visual servoing scheme consists of a closed-loop control approach which uses visual information feedback to control the movement of a robotic system. This data, called visual features, can be 2D or 3D. This thesis deals with the development of a new generation of 2D direct visual servoing methods in which the signal control inputs are the coefficients of a multiscale image representation. Specially, we consider the use of multiscale image representations that are based on discrete wavelet and shearlet transformations. This kind of representations allows us to obtain several descriptions of the image based on either low or high frequencies levels. Indeed, high coefficients in the wavelet or in the shearlet transformation of the image correspond to image singularities. This thesis has begun with the development of a shearlet-based visual servoing for ultrasound imaging that has performed well in precision and robustness for this medical application. Nevertheless, the main contribution is a framework allowing us to use several multi-scale representations of the image. It was then tested with conventional white light camera and with an optical coherence tomography imaging system with nominal and unfavorable conditions. Then, the wavelet and the shearlet based methods showed their accuracy and their robustness in several conditions and led to the use of both visual servoing and compressed sensing as the main perspective of this work.
2

Komprese obrazu pomocí vlnkové transformace / Image Compression Using the Wavelet Transform

Kaše, David January 2015 (has links)
This thesis deals with image compression using wavelet, contourlet and shearlet transformation. It starts with quick look at image compression problem a quality measurement. Next are presented basic concepts of wavelets, multiresolution analysis and scaling function and detailed look at each transform. Representatives of algorithms for coeficients coding are EZW, SPIHT and marginally EBCOT. In second part is described design and implementation of constructed library. Last part compare result of transforms with format JPEG 2000. Comparison resulted in determining type of image in which implemented contourlet and shearlet transform were more effective than wavelet. Format JPEG 2000 was not exceeded.

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