Kim, and Huang (2008), the watermark is embedded in an affine
invariant domain by using Fourier–Mellin transform, generalized
Radon transform, pseudo-Zernike moments, geometric moments,
and histogram shape respectively. In Zhang, Cheng, Qiu, and
Cheng (2008), an algorithm of leveled watermarking is proposed.
This algorithm is based on the curvelet transform and does not
involve the original image at the detector end or exhaustive direc-
tion search. Watermark bits with different robustness are embed-
ded in each scale and one bit is carried by one wedge. The
coefficients selection for watermarking is based on the conception
that the coefficient energy is proportional to its directional sensi-
tivity. Tai, Yeh, and Chang (2009) presented a reversible data hid-
ing scheme based on histogram modification. They exploit a
binary tree structure to solve the problem of communicating pairs
of peak points. Distribution of pixel differences is used to achieve
large hiding capacity while keeping the distortion low. They also
adopt a histogram shifting technique to prevent overflow and
underflow. Despite that they are robust against global affine
transformations, those techniques involving invariant domain
suffer from implementation issues and are vulnerable to mixed
attacks.
Template insertion: Another solution to cope with geometric
distortions is to identify the transformation by retrieving artifi-
cially embedded references. Liu, Zheng, and Zhao (2007) presents
an image rectification scheme that can be used by any image
watermarking algorithm to provide robustness against rotation,
scaling and translation (RST). In the watermarking, a small block
is cut from the log-polar mapping (LPM) domain as a matching
template, and a new filtering method is proposed to compute
the cross-correlation between this template and the magnitude
of the LPM of the image having undergone RST transformations
to detect the rotation and scaling parameters. Zhang, Li, and
Wang (2008) designs look-up table (LUT) according to the distor-
tion of LUT embedding. A new practical reduced-distortion LUT
design method is developed for robust data hiding. A Gaussian
mixture model and a related expectation-maximization algorithm
based method are employed to model the statistical distribution
of the host image. The statistical model is used to select signifi-
cant wavelet coefficients of the host image for data hiding. Boato
and Conotter (2009) present an innovative and flexible tool suit-
able to assess the robustness of digital watermarking techniques,
by introducing a novel metric based on the perceptual quality
evaluation for unmarked images. Genetic algorithms (GA) per-
form the search of optimal parameters to be assigned to each im-
age processing operator, as well as the order they need to be
applied in, to remove the watermark from the content while
keeping the perceptual quality of the resulting image as high as
possible. However, this kind of approach can be tampered with
by the malicious attack. As for random bending attacks, the tem-
plate-based methods will be incompetent to estimate the attack
parameters.
Feature-based: The last category is based on media features. Its
basic idea is that, by binding the watermark with the geometri-
cally invariant image features (Local Feature Region, LFR), the
watermark detection can be done without synchronization error.
Lee, Lee, and Lee (2007) propose a geometrically invariant water-
marking method that uses circular Hough transform for water-
mark synchronization. Through circular Hough transform, the
circular features are extracted that are invariant to geometric dis-
tortions. Based on Harris–Laplace detector and scale-space the-
ory, Wang, Wu, and Niu (2007) propose a feature-based digital
image watermarking scheme in DFT domain. In Li and Guo
(2009), present a novel robust image watermarking scheme for
resisting geometric distortions. Watermark synchronization is
first achieved by local invariant regions which can be generated
using scale normalization and image feature points. The water-
mark is embedded into all the local regions repeatedly in spatial
domain. Deng, Gao, Li, and Tao (2009) give a content-based
watermarking scheme that combines the invariant feature extrac-
tion with watermark embedding by using Tchebichef moments.
Pham, Miyaki, Yamaski, and Aizama (2008) present a robust ob-
ject-based watermarking algorithm using the local image feature
in conjunction with a data embedding method based on DCT, and
the digital watermark is embedded in the DCT domain of ran-
domly generated blocks in the selected object region. Gao, Deng,
and Li (2010) propose a new image watermarking scheme by
incorporating the advantages of the affine invariant point detec-
tor and the orientation alignment seamlessly. The affine invariant
point detector is adopted to extract Affine Covariant Regions
(ACRs). The graph theoretical clustering algorithm is then em-
ployed to select a set of nonoverlapped ACRs for watermark
embedding. Singhal, Lee, and Kim (2009) propose a robust image
watermarking algorithm using local Zernike moments, which are
computed over circular patches around feature points. The pro-
posed algorithm locally computes Zernike moments and modifies
them to embed watermarks, achieving robustness against crop-
ping and local geometric attacks. Moreover, to deal with scaling
attacks, the proposed algorithm extracts salient region parame-
ters, which consist of an invariant centroid and a salient scale,
and transmits them to the decoder. The parameters are used at
the decoder to normalize a suspect image and detect watermarks.
In Li, Guo, and Pan (2010), a new robust image watermarking
scheme is presented by combining scale-space feature point
based watermark synchronization and NSCT based watermark
embedding. Watermark synchronization is achieved based on
the local circular regions, which can be generated using the
scale-invariant feature transform (SIFT). In the encoder, the
watermark is embedded into the NSCT coefficients in a con-
tent-based and rotation-invariant manner by odd–even quantiza-
tion. In the decoder, the watermark can be extracted directly
from the local regions using the proposed coefficient property
detector (CPD). It is not difficult to see that the feature-based ap-
proaches are better than others in terms of robustness. However,
some drawbacks indwelled in current feature-based schemes re-
strict the performance of watermarking system. First, the feature
point extraction is sensitive to image modification. Second, the
computational complexity in calculating the features of an image
before watermark detection is added. Third, the volume of water-
mark data is lesser.
Generally speaking, the above-mentioned research efforts con-
centrated on developing the watermarking schemes for gray
images, and the watermarking schemes for color images are very
few. While, in ubiquitous multimedia applications, color images
are basic components of multimedia systems, such as video sys-
tems based on current video compression standards, MPEG-1,
MPEG-2, MPEG-4, and further MPEGs. Hence, it is crucial to first
develop effective watermarking techniques for color images. In
Peng and Liu (2008), a new semi-fragile watermarking scheme
for color image authentication is proposed based on spatiotempo-
ral chaos and singular value decomposition (SVD). The watermark
is embedded into the singular values of the blocks within wavelet
subband. In order to enhance the security, spatiotemporal chaos is
employed to select the embedding positions for each watermark
bit as well as for watermark encryption. Tsui, Zhang, and Androut-
sos (2008) encodes the L
*
a
*
b
*
components of color images and
watermarks are embedded as vectors by modifying the Spatiochro-
matic Discrete Fourier Transform (SCDFT) coefficients and using
the Quaternion Fourier Transform (QFT). However, it was found
that even very small geometric distortions, such as RST attacks,
could reduce the detector’s ability of detecting watermarks. Arash
and Shohreh (2008) proposed a novel method to utilize the Princi-
pal Component Analysis (PCA) in the neighborhoods of an image in
2082 P.-P. Niu et al. / Expert Systems with Applications 38 (2011) 2081–2098