Multidim Syst Sign Process
ably corrupted by noise during acquisition and transmission. In the last decades, a large
number of methods have been proposed for removing noise, thus leading to improvements
in denoising performance.
Several color-image-denoising techniques, which can remove noise by a point wise-
varying local mask, have been proposed in the spatial domain (Tschumperle and Deriche
2005). Takeda et al. (2007) constructed a local model of an image with a polynomial func-
tion. The filtered image is obtained by modifying coefficients that are calculated by weighted
least squares regression. Another denoising framework can remove noise by computing the
differences in spatial values among neighboring pixels (Coifman and Meer 2002; Buades et
al. 2006). The image-denoising algorithm based on partial differential equation was proposed
by Perona and Malik (1990).
The challenge faced by any image-denoising algorithm is the removal of noise while
producing a sharp image without information loss. Awate and Whitaker (2006), Baudes et
al. (2005) proposed a new bilateral filter based on patches. Non-local techniques obtain the
denoised image by minimizing the penalty term on the average weighted distance between
an image patch and all other patches (Kervrann and Boulanger 2006, 2008). Elad and
Aharon (2006) proposed kernel singular value decomposition (KSVD), which is a signif-
icant denoising method. A new denoising algorithm was proposed in Chatterjee and Milan-
far (2009) by combining dictionary-based methods with regression-based methods. Dabov
et al. (2007) proposed color-block matching and 3D filtering (CBM3D), which can group
similar patches and perform filtering in the transform domain. This dictionary-based algo-
rithm provides implicit modeling for natural images. Other color-image-denoising meth-
ods based on explicit models have been proposed in Liu et al. (2008), Muresan and Parks
(2003), Zhang et al. (2010). Then the patch-based locally optimal Wiener (PLOW) filter-
ing to exploit the patch redundancy of an image was proposed by Chatterjee and Milanfar
(2012).
Another class of image-denoising techniques is based on the transform domain. The noisy
image is first transformed into the frequency domain. Smaller coefficients usually correspond
to higher frequency components of the image signal, which are dominated by noise. There-
after, transformed coefficientscan be processed by using the maximum a posteriori probability
estimation technique. Typical transform domain methods for image denoising include wavelet
(Rajpoot and Butt 2012; Vo et al. 2011; Hsia et al. 2012), Bayes least square–Gaussian scale
mixture (BLS–GSM) method (Portilla et al. 2003), and contourlet (Sheng and Zhen 2009;
Haji and Bui 2012). The state-of-the-art image-denoising method in the transform domain is
a high-order SVD (HOSVD) (Rajwade and Rangarajan 2013).
Existing denoising methods first remove the noise in color images by separating the
image into R, G, and B channels before using the denoising algorithm on each channel.
The denoised image loses large amounts of information because of the inherent relation-
ships among the three components of the color image (i.e., R, G, and B). The proposed
algorithm in this paper can process the color image as a whole instead of separating it into
components. A good trade-off can be achieved between the denoising effect and information
preservation.
The rest of this paper is organized as follows. Section 2 reviews the theory of
reduced quaternion (RQ) matrix (RQM). Section 3 provides the details of the proposed
RQM singular value decomposition (RQMSVD). Section 4 presents the new color-image-
denoising method based on RQMSVD. Section 5 shows the experimental validation of
the proposed algorithm and compares the proposed algorithm with several recently pro-
posed denoising algorithms in terms of visual quality. Finally, the conclusion is given in
Sect. 6.
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