Published in IET Image Processing
Received on 5th June 2012
Revised on 29th March 2013
Accepted on 21st April 2013
doi: 10.1049/iet-ipr.2013.0085
ISSN 1751-9659
Construction method of three-channel non-separable
symmetric wavelets with arbitrary dilation matrices
and its applications in multispectral image fusion
Bin Liu
1
, Kai Li
1
, Weijie Liu
2
, Fei Liu
1
1
School of Mathematics and Computer Science, Hubei University, Wuhan 430062, People’s Republic of China
2
Computer School, Wuhan University, Wuhan 430072, People’s Republic of China
E-mail: liub@hubu.edu.cn
Abstract: Image fusion method based on separable discrete wavelet transform has block effect and the spatial resolution is lower
in the fusion result images. The design method of filter bank relies on the form of the dilation matrices in the image fusion method
based on three-channel non-separable wavelet. To resolve these problems, a new construction method of the filter banks based on
three-channel non-separable symmetric wavelet with arbitrary dilation matrices is presented. A new multispectral image fusion
method based on this kind of wavelet filter bank is proposed. An example of the filter bank with those properties is constructed
and applied to the fusion of multispectral image and panchromatic image. The experiment results show that this method has good
visual effect. The fusion performance of the proposed method is better than that of the other methods in terms of several
frequently used and the latest metrics.
1 Introduction
In a variety of remote sensing and mapping application, the
fusion of multispectral and panchromatic images, with
complementary spectral and spatial characteristics, is an
important issue. An effective fusion technique provides a
single high-resolution multispectral image with high spatial
and spectral resolution simultaneously. These well-fused
images can be a useful tool for feature detection, change
monitoring, urban analysis and land cover classification [1, 2].
To date, many techniques and software tools for fusing
images have been developed. The well-known methods
include the Brovey method, the intensity-hue-saturation
(IHS) colour model [3], principal component analysis
(PCA) [4], amelioration de la resolution spatiale par
injection de structures (ARSIS), the wavelet-based method
and other multiresolution analyses in cluding separable
discrete wavelet transform (DWT) [ 5], ridgelet [6], curvelet
[7] and contourlet [8]. The most widely used procedure in
panchromatic and multispectral images fusion are the IHS
transform method and the DWT mergers based on Mallat
algorithm. However, the two methods have their
insufficiencies. The method of IHS transform can get high
spatial resolution image, but the fused image may seriously
lose the spectral information of the original MS image. A
fused image with good spectral information can be created
by the separable wavelet based on Mallat algorithm, but it
is low in spatial resolution and there is block effect in the
fused image because the subsampling is done when images
are decomposed and reconstructed. To overcome the
disadvantages of the IHS fusion technique and those of the
wavelet fusion technique, and to explore their potential for
further improvement, Zhang and Hong proposed a fusion
method combining IHS transform and DWT, which
improved the fusion quality to some extent [9]. However,
this algorithm is not shift-invariant which is caused by the
decimation process. Without shift-invariance, slight shifts in
the input images will produce variation in the wavelet
coefficients that might introduce artefacts in the
reconstructed image. Furthermore, the standard DWT
involved in this method is poor in representation of features
with orientations that are not horizontal or vertical, wh ich is
a result of separate filtering in these directions, there are
block effect in fused image [9]. To resolve these problems,
we present a unified construction method of three-channel
non-separable symmetric wavelet filter banks. The filter
banks are isotropic and symmetric and can preserve features
at all orientation better. When the undecimated
non-separable wavelet transform with this kind of filter
bank is applied to image fusion, it is shift-invariant and
would not cause phase distortion in the fused images.
Our group has studied the multispectral image fusion
methods based on three-channel non-separable wavelets
[10, 11]. These methods have good fusion effect. However,
the filter banks constructed in literature [10]haveno
symmetry. The filter banks constructed in [11] have
symmetry, but construction method relies on some special
matrix such as [2, −1; 1, 1]. In this paper, a general
construction method of three-channel non-separable
symmetric wavelet filter bank with arbitrary dilation
matrices has been proposed and the filter banks are applied
to the fusion of multispectral and panchromatic images.
www.ietdl.org
IET Image Process., 2013, Vol. 7, Iss. 7, pp. 679–685
doi: 10.1049/iet-ipr.2013.0085
679
© The Institution of Engineering and Technology 2013