www.seipub.org/ijc
International Journal on Communications (IJC) Volume 3, 2014
A Robust Color Image Watermarking Based on SVD and DWT Li ZHANG*, Jia Wei XIAO, Jing Yun LUO Institute of Information Engineering, Shenzhen University, Shenzhen Guangdong 518060, China *
wzhangli@szu.edu.cn; jiaweixiao@szu.edu.cn; jingyunluo@szu.edu.cn
Abstract A robust color image watermarking based on DWT – SVD (Singular value decomposition) is proposed. Firstly, color image is transformed to YUV from RGB spatial domain. Luminance component Y is performed DWT and then singular value decomposition is applied to obtain singular values. Arnold transform and DWT are performed for the gray watermarks. Watermark is embedded into singular values, which are all from frequency bands of the last two layers. Watermark can be extracted from all attack images in the stirmark benchmark. The robustness can be reflected by experimental results in this algorithm. Keywords Digital Watermarking; SVD; DWT
Introduction Electronic products are more and more important in modern society. Dissemination and replication of digital products are getting easier. More and more people infringe electronic products in order to resist different kinds of infringements and protect the electronic products. Digital watermarking technology emerges as the times requiring. Digital watermark is a kind of copyright protection information and owners can read it out while unauthorized users can not easily remove it. Invisibility and robustness should be considered in valid watermarking algorithm. Compromises between invisibility and robustness are needed to get better results in embedding process. Feng Shi split low-frequency part of the original image into 4×4 data blocks, decomposed the singular value of each piece and calculated the largest singular value of each block. Low frequency information of watermark was embedded into these singular values. But it is not very robust to rotation attack according to experimental results. Kapre Bhagyashri S selected full band frequency to hide watermark in the three channel of YUV color space. In each level of decomposition, image was decomposed into four bands of frequencies and SVD was performed. Watermark was hidden in the singular values. Then
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ISVD and IDWT were applied to get watermarked image. However, watermark can not be extracted when strength of noise attack is higher. In this paper, a new watermarking algorithm that embeds a gray watermark into the color image is proposed based on SVD and DWT. Watermark is embedded in luminance component Y. All frequency coefficients of watermark are embedded into singular values of frequency bands, which are all from last two layers of Y. Experimental results demonstrate that the proposed watermarking has good robustness against attacks produced by stirmark benchmark. This paper is organized as follows: In section 2 the YUV color model is introduced. In section 3 digital watermark embedding and extracting algorithm are presented in detail. Experimental results of stirmark benchmark are described in section 4. Finally, in section 5 the conclusion is given. Background Color space is a three-dimensional coordinate system whose each color is indicated by a dot. Color image is transformed to YUV from RGB spatial domain. Conversions between RGB and YUV are as follows:
Y 0.299 R 0.587G 0.114 B U 0.16874 R 0.33126G 0.5B 128 V 0.5R 0.41869G 0.08131B 128
(1)
R Y 1.402(V 128) G Y 0.34414(U 128) 0.71414(V 128) B Y 1.772(U 128)
(2)
Where, Y represents luminance component. U and V mean that chrominance signal. Proposed Watermarking Algorithm In this section, the proposed watermarking algorithm including embedding and extracting process will be described in detail.