Progressive transmission of pseudo-color images. Appendix 1: Item 4

The transmission of digital images can require considerable channel bandwidth. The cost of obtaining such a channel can be prohibitive, or the channel might simply not be available. In this case, progressive transmission (PT) can be useful. PT presents the user with a coarse initial image approximation, and then proceeds to refine it. In this way, the user tends to receive information about the content of the image sooner than if a sequential transmission method is used. PT finds application in image data base browsing, teleconferencing, medical and other applications. A PT scheme is developed for use with a particular type of image data, the pseudo-color or color mapped image. Such images consist of a table of colors called a colormap, plus a 2-D array of index values which indicate which colormap entry is to be used to display a given pixel. This type of image presents some unique problems for a PT coder, and techniques for overcoming these problems are developed. A computer simulation of the color mapped PT scheme is developed to evaluate its performance. Results of simulation using several test images are presented

Some new developments in image compression

This study is divided into two parts. The first part involves an investigation of near-lossless compression of digitized images using the entropy-coded DPCM method with a large number of quantization levels. Through the investigation, a new scheme that combines both lossy and lossless DPCM methods into a common framework is developed. This new scheme uses known results on the design of predictors and quantizers that incorporate properties of human visual perception. In order to enhance the compression performance of the scheme, an adaptively generated source model with multiple contexts is employed for the coding of the quantized prediction errors, rather than a memoryless model as in the conventional DPCM method. Experiments show that the scheme can provide compression in the range from 4 to 11 with a peak SNR of about 50 dB for 8-bit medical images. Also, the use of multiple contexts is found to improve compression performance by about 25% to 35%;The second part of the study is devoted to the problem of lossy image compression using tree-structured vector quantization. As a result of the study, a new design method for codebook generation is developed together with four different implementation algorithms. In the new method, an unbalanced tree-structured vector codebook is designed in a greedy fashion under the constraint of rate-distortion trade-off which can then be used to implement a variable-rate compression system. From experiments, it is found that the new method can achieve a very good rate-distortion performance while being computationally efficient. Also, due to the tree-structure of the codebook, the new method is amenable to progressive transmission applications

Progressive transmission of digital recurrent video.

by Wai-Wa Wilson Chan.Thesis (M.Sc.)--Chinese University of Hong Kong, 1992.Includes bibliographical references (leaves 79-80).Chapter 1. --- Introduction --- p.1Chapter 1.1 --- Problem under study and scope --- p.4Chapter 1.2 --- Review of relevant research --- p.6Chapter 1.3 --- Objectives --- p.11Chapter 2. --- Theory --- p.12Chapter 2.1 --- Multi-resolution representation of digital video --- p.13Chapter 2.2 --- Performance measure of progressive algorithm --- p.15Chapter 2.3 --- Introduction to depth pyramid --- p.35Chapter 2.4 --- Introduction to spatial pyramid --- p.37Chapter 2.5 --- Introduction to temporal pyramid --- p.42Chapter 2.6 --- Proposed algorithm for progressive transmission using depth-spatial-temporal pyramid --- p.46Chapter 3. --- Experiment --- p.55Chapter 3.1 --- Simulation on depth pyramid --- p.59Chapter 3.2 --- Simulation on spatial pyramid --- p.60Chapter 3.3 --- Simulation on temporal pyramid --- p.62Chapter 3.4 --- Simulation on algorithm for progressive transmission using depth-spatial-temporal pyramid --- p.64Chapter 4. --- Conclusions and discussions --- p.74Chapter 5. --- Reference and Appendix --- p.7

Bedarfsgesteuerte Bildübertragung mit Regions of Interest und Levels of Detail für mobile Umgebungen

Die hier entwickelten Konzepte der bedarfsgesteuerten Bildübertragung erlauben es, für wählbare Bildregionen die benötigte Detaillierungsstufe festzulegen und Bildbereiche redundanzfrei zu verfeinern. Dadurch kann die Übertragung großer Bilder an beschränkte Ressourcen in mobilen Umgebungen angepasst werden. Ein allgemeines waveletbasiertes Kodier- und Übertragungsverfahren und ein spezielles progressives Kodierverfahren für Farbtabellenbilder werden entworfen. Zur effizienten Ausnutzung von Bildschirmfläche und Bitrate wird die interaktive Technik des Rechteckigen Fisheye-View entwickelt.The proposed concept of demand-driven image transmission allows to define the required level of detail for arbitrary image regions and to refine image areas without the need for redundant data transmissions. By this mechanism the image transmission can be better adapted to the limited resources in mobile environments. A general wavelet-based method for image encoding and transmission and a specific encoding method for palettized images are designed. For the efficient use of screen area and transmission bit rate the interactive technique of the Rectangular Fish Eye View is developed