DAT ENCRYPTION TECHNIC

1. A New Secure Image Transmission Technique via
Secret-fragment-visible Mosaic Images by integer-
to-integer wavelet transform
Reversible integer-to-integer (ITI) wavelet transforms are
studied in the context of image coding. Considered are matters
such as transform frameworks, transform design techniques, the
utility of transforms for image coding, and numerous practical
issues related to transforms. The generalized reversible ITI
transform (GRITIT) framework, a single unified framework for
reversible ITI wavelet/block transforms, is proposed. This new
framework is then used to study several previously proposed
frame-works and their interrelationships. For example, the
framework based on the overlapping rounding transform is
shown to be a special case of the lifting framework with only
trivial extensions. The applicability of the GRITIT framework
for block transforms is also demonstrated. Throughout all of this
work, particularly close attention is paid to rounding operators
and their characteristics. Strategies for handling the
transformation of arbitrary-length signals in a nonexpansive
manner are considered (e.g., symmetric extension, per-displace-
step extension). Two families of symmetry-preserving
transforms (which are compatible with symmetric extension) are
introduced and studied. We characterize transforms belonging to
these families. Some new reversible ITI structures that are useful
for constructing symmetry-preserving transforms are also
proposed. A simple search-based design technique is explored as

2. means for finding effective low-complexity transforms in the
above-mentioned families. In the context of image coding, a
number of reversible ITI wavelet transforms are compared on
the basis of their lossy compression performance, lossless
compression performance, and computational complexity. Of
the transforms considered, several were found to perform
particularly well, with the best choice for a given application
depending on
the relative importance of the preceding criteria. Reversible ITI
versions of numerous transforms are also compared
to their conventional (i.e., non-reversible real-to-real)
counterparts for lossy compression. At low bit rates, reversible
ITI and conventional versions of transforms were found to often
yield results of comparable quality. Factors affecting
the compression performance of reversible ITI wavelet
transforms are also presented, supported by both experimental
data and theoretical arguments.
In addition to this work, the JPEG-2000 image compression
standard is discussed. In particular, the JPEG-2000
Part-1 codec is described, analyzed, and evaluated.