Gray Scale and Color Medical Image Compression by Lifting Wavelet; Bandelet and Quincunx Wavelets Transforms : A Comparison Study

The Quincunx wavelet , the lifting Scheme wavelet and the Second generation bandelet transform are a new method to offer an optimal representation for image geometric; we use this transform to study medical image compressed using the Quincunx transform coupled by SPIHT coder. We are interested in compressed medical image, In order to develop the compressed algorithm we compared our results with those obtained by this transforms application in medical image field. We concluded that the results obtained are very satisfactory for medical image domain. Our algorithm provides very important PSNR and MSSIM values for medical images compression

Rate scalable image compression in the wavelet domain

This thesis explores image compression in the wavelet transform domain. This the- sis considers progressive compression based on bit plane coding. The rst part of the thesis investigates the scalar quantisation technique for multidimensional images such as colour and multispectral image. Embedded coders such as SPIHT and SPECK are known to be very simple and e cient algorithms for compression in the wavelet do- main. However, these algorithms require the use of lists to keep track of partitioning processes, and such lists involve high memory requirement during the encoding process. A listless approach has been proposed for multispectral image compression in order to reduce the working memory required. The earlier listless coders are extended into three dimensional coder so that redundancy in the spectral domain can be exploited. Listless implementation requires a xed memory of 4 bits per pixel to represent the state of each transformed coe cient. The state is updated during coding based on test of sig- ni cance. Spectral redundancies are exploited to improve the performance of the coder by modifying its scanning rules and the initial marker/state. For colour images, this is done by conducting a joint the signi cant test for the chrominance planes. In this way, the similarities between the chrominance planes can be exploited during the cod- ing process. Fixed memory listless methods that exploit spectral redundancies enable e cient coding while maintaining rate scalability and progressive transmission. The second part of the thesis addresses image compression using directional filters in the wavelet domain. A directional lter is expected to improve the retention of edge and curve information during compression. Current implementations of hybrid wavelet and directional (HWD) lters improve the contour representation of compressed images, but su er from the pseudo-Gibbs phenomenon in the smooth regions of the images. A di erent approach to directional lters in the wavelet transforms is proposed to remove such artifacts while maintaining the ability to preserve contours and texture. Imple- mentation with grayscale images shows improvements in terms of distortion rates and the structural similarity, especially in images with contours. The proposed transform manages to preserve the directional capability without pseudo-Gibbs artifacts and at the same time reduces the complexity of wavelet transform with directional lter. Fur-ther investigation to colour images shows the transform able to preserve texture and curve.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Progressive Meshes in an Operational Rate-Distortion Sense with Application to Terrain Data

This paper presents an efficient simplification method for regular meshes obtained with a binary subdivision scheme. Our mesh connectivity is constrained with a quadtree data structure. We propose a quadtree built especially for this class of meshes having a constant-time traversal property. We introduce a rate-distortion (RD) framework to decimate the mesh and build a progressive representation for the model. We propose to achieve the RD-optimal solutions for our quadtree-restricted setting: to obtain the optimal solutions, we show how to find the vertex in the quadtree yielding the best RD trade-off and then perform optimizations at variable rate, where the rate is given by a cost function (for example the number of triangles). All previous methods are restricted to constant rate optimization only. We compare the optimal approach to its greedy counterpart. We give computationally optimal formulations for all our algorithms on the quadtree. We apply our technique to a large dataset of terrains and give extensive experimental results

Multiskalenmethoden zur Kompression und interaktiven Verarbeitung großer Datenmengen

Die vorliegende Arbeit beschaeftigt sich mit der Entwicklung von Verfahren zur interaktiven graphischen Darstellung (Visualisierung) grosser Datenmengen. Insbesondere betrifft dies adaptiv hierarchische Verfahren zur Darstellung von Oberflaechen und Isolinien, sowie zur Schnittbildung, Isoflaechen- Extraktion und Volumendarstellung. Zum einen wird die Berechnung von Fehlerindikatoren und Fehlerschranken zur Steuerung der adaptiven Verfeinerung, insbesondere Saturierungstechniken zur Vermeidung haengender Knoten und Berechnung von minmax-Schranken, zur Fokussierung, sowie zur Topologie-Erhaltung und kontrollierten Topologie- Vereinfachung betrachtet. Weiterhin werden Kompressionsverfahren basierend auf Wavelets mit Hilfe des lifting Schemas, sowie raumfuellenden Kurven und relativen Sprungzeigern fuer hierarchische Triangulierungen entwickelt. Schliesslich wird die Beschleunigung der Visualisierungsalgorithmen durch Parallelisierung am Beispiel der Isoflaechen-Extraktion, sowie durch hierarchische Sortierung bei der Darstellung mehrerer transparenter Isoflaechen untersucht. Die Anwendungsgebiete der Verfahren liegen dabei in den Bereichen GIS, Meteorologie, Bildkompression, medizinische Bildverarbeitung und Chemie.This work is concerned with the development of methods for the interactive visualization of large data sets. Of special concern are adaptive hierarchical methods for the respresentation of surfaces, isolines, slicing, isosurface extraction and volume rendering. One major focus is the computation of error indicators and error bounds to guide the adaptive refinement. This especially concerns saturation techniques for the preventon of hanging nodes, for the computation of minmax bounds, for focussing, and for topology preservation and controlled topology simplification. The second emphasis are compression methods based on wavelets using the lifting scheme as well as space-filling curves and relative branch pointers for hierarchical triangulations. Furthermore, the acceleration of the visualization algorithms by parallelization for example in isosurface extraction and hierarchical sorting for the rendering of multiple transparent isosurfaces is considered. The application areas of the presented methods are geographical information systems, meteorology, image compression, medical imaging, and chemistry