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Still image compression by nonseparable wavelets on the quincunx lattice

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Andrews, RJ (2002) Still image compression by nonseparable wavelets on the quincunx lattice. PhD thesis, University of Tasmania.

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Abstract

The recent unification of wavelet and subband theories has allowed the creation
of a new field of investigation for the efficient compression of digital images:
wavelet compression. It has seen remarkable improvements in compression results
over the previous generation of DCT-based image compression schemes. The focus
of research in this field has, however, been almost exclusively in the separable
domain, which uses one-dimensional transforms.
The use of truly nonseparable wavelet transforms on two-dimensional image
signals has been largely ignored. The purpose of this Thesis is to investigate more
thoroughly this largely untouched field of wavelet-based image compression.
In this Thesis we discuss in depth the techniques for using multidimensional
wavelet transforms and subband coding for image compression and provide results
for extending existing compression techniques to the quincunx domain. Various
results covering a number of coding methodolgies are presented using the quincunx
wavelet transform to demonstrate its advantages and disadvantages when
compared to the separable decomposition method. Novel techniques are developed
for the representation and storage of quincunx sampled images allowing
in-place wavelet transforms to be performed in real-time. A novel extension to
the Shapiro zero-tree compression method is developed which predicts and exploits,
during coding, visually unimportant areas without the need for transmitting
side-information. Results are presented which show that this process leads to
significantly higher perceived image quality without increasing the bit-rate.
Several advantageous psychovisual properties of the quincunx resampling lattice
are exploited in the creation of various extensions to simple compression methods.
Results isolating the effects of utilizing these properties are presented.
We find that in general separable wavelet transforms perform better than their
quincunx counterparts for bit-rate versus perceived quality of reconstruction, despite
the quincunx resampling structure possessing inherent advantages over rectangular
resampling. This is mainly attributed to the state of non-separable subband
theory and filter design which has not progressed to a state where it is possible
to achieve the same quality of filter design as exists in the one dimensional
case.

Item Type: Thesis (PhD)
Keywords: Image processing, Image compression, Lattice theory, Wavelets (Mathematics)
Copyright Holders: The Author
Copyright Information:

Copyright 2002 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2002. Includes bibliographical references

Date Deposited: 25 Nov 2014 00:51
Last Modified: 23 Aug 2017 07:19
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