FEATURE-BASED DIGITAL WATERMARKING FOR REMOTE SENSING IMAGES
P.-H. Hsu“ * and C -C. Chen *
* Dept. of Civil Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Rd., Taipei City 10617, Taiwan —
(hsuph, d98521018)@ntu.edu.tw
Commission III, ICWG III/VII
KEY WORDS: Watermarking, Feature, Extraction, Transformation, Quality, Robustness
ABSTRACT:
With the rapid development of information and communication technology, people can acquire and distribute many kinds of digital
data more conveniently than before. The consequence is that the "copyright protection" which prevents digital data from been
duplicated illegally should be paid much more attention. Digital watermarking is the process of embedding visible or invisible
information into a digital signal which may be used to verify its authenticity or the identity of its owners. In the past, digital
watermarking technology has been successfully applied to the “copyright protection" of multimedia data, however the researches and
applications of applying digital watermarking to geo-information data are still very inadequate. In this study, a novel digital
watermarking algorithm based on the scale-space feature points is applied to the remote sensing images, and the robustness of the
embedded digital watermark and the impact on satellite image quality are evaluated and analysed. This kind of feature points are
commonly invariant to Image rotation, scaling and translation, therefore they naturally fit into the requirement of geometrically
robust image watermarking. The experiment results show almost all extracted watermarks have high values of normal correlation and
can be recognized clearly after the processing of image compression, brightness adjustment and contrast adjustment. In addition,
most of the extracted watermarks are identified after the geometric attacks. Furthermore, the unsupervised image classification is
implemented on the watermarked images to evaluate the image quality reduction and the results show that classification accuracy is
affected slightly after embedding watermarks into the satellite images.
1. INTRODUCTION
With the rapid development of information technology (IT) and
communication technology (CT), people can acquire and
distribute different kind of digital data more convenient than
before. The consequence is that the "copyright protection"
which prevent digital data from been duplicated illegally should
be paid much more attention. Digital watermarking, which is a
kind of information hiding technologies, is the process of
embedding visible or invisible information into a digital signal
which may be used to verify its authenticity or the identity of its
owners. In the past, digital watermarking technology has been
successfully applied to the "copyright protection" of various
kinds of digital multimedia data, however the researches and
applications of applying digital watermarking to geo-
information data are still very inadequate. In this study, the
digital watermarking technology is applied to the remote
sensing images, and the robustness of the embedded digital
watermark and the impact on satellite image quality are
evaluated and analysed.
A digital watermark is called robust if it could be detectable
completely even when the watermarked data is subject to
unintentional or intentional data modifications (or attacks). In
addition to the robustness of watermark, the quality of original
data after embedding the digital watermark also should be
preserved. In order to satisfy these two basic requirements
simultaneously, the digital watermarking algorithm should be
developed according to the characteristics of the geospatial data
and their applications. Hsu and Chen (2011) have proposed a
novel algorithm that the digital watermark was embedded into
the photogrammetric images, and the robustness of the
* Corresponding author..
embedded digital ^ watermark and the impact on
photogrammetric image quality are evaluated. In this study, this
algorithm has been improved for the applications of satellite
images. Firstly, the embedding and extracting algorithms of
digital watermark should be robust to resist the geometric
attacks such as image rotation, scaling, and translation (RST).
Secondly, the digital watermark techniques should not result in
the geometric deformation or radiometric distortion on the
original image data. For satellite images, the geometric or
radiometric distortion not only reduces the human's visual
sensation but also affects the image processing results, such as
the image matching, image classification and image
measurements.
The robust image watermarking algorithm proposed in this
study is based on the scale-space feature points to fulfill the two
above-mentioned requirements. This kind of feature points are
commonly invariant to rotation, scaling and translation,
therefore they naturally fit into the requirement of geometrically
robust image watermarking. For this reason, the scale-invariant
feature transform (SIFT) is used to detect the scale-space feature
points, than some non-overlapped circular regions surrounding
the feature points are selected to embed the watermark.
Furthermore, the watermark is adjusting the watermark intensity
in accordance with the texture sensitive values of the wavelet
packet transform of the circular regions to avoid the reduction
of the satellite image quality. :
In the experiments of this study, two data set from WorldView-
2 and Formosat-2 satellites are used to test the performance of
our proposed watermarking method. In the test of the watermark
robustness, almost all extracted watermarks have high values of
normal correlation and can be recognized clearly after the
processing X
contrast adji
extracted Wi
most of thi
geometric a
translation
classificatior
evaluate the
classificatior
watermarks |
2. DIGI
Digital wat
embedding
imagery wh
identity of i
trademark, s
generated fr
and major
images are c
2.1 Review
Barni et al.
algorithm u
wavelet trar
adjusted to
an unsuperv
Ziegeler e!
watermarkir
be directly «
analytic inte
primary im
watermarkii
impact of
performanc
proposed a
on DWT, tt
attacks. Ch:
algorithm |
transform,
satellite in
resist image
and compre
22 Majoi
The study
focus on th
1. The
of th
valid
matc]
2. Geon
the
relati
geog
pixel
robu:
attac
of w:
