An Efficient Image Watermarking Scheme

based on DWT-DFRNT Dual Transform Method

for Digital Content Protection

M. Kim1 , D. Li2, , S. Hong

1

1 Department of Computer and Information Sciences, Towson University,

Towson, Maryland, USA 2 Department of Computer Science, University of Yanbian,

Yanji, China

leader1223@ybu.edu.cn

Abstract. With the rise of digital contents, their copyright protection has

emerged as a serious issue and digital watermarking can be introduced as an

effective method for solving the issue. In this paper, we propose a new digital

image watermarking algorithm based on the dual transform method, discrete

wavelet transform (DWT) and discrete fractional random transform (DFRNT).

We generate a watermark through a two-dimensional (2D) barcode and the

block code encoder, and the generated watermark image is embedded into

DWT-DFRNT using quantization technique in order to ensure robustness and

security of the algorithm. Experimental results present that our proposed

method has improved the extraction performance of watermark and ensured the

imperceptibility, security, and robustness of the watermark against image signal

processing attacks such as compression and noise adding by increasing the

hidden computational complexity of information and combining DWT and

DFRNT transforms.

Keywords: Watermarking, Discrete Wavelet Transform (DWT), Discrete

Fractional Random Transform (DFRNT), 2D-barcode, Quantization

1 Introduction

The number of digital media contents has continued to increase rapidly due to

advances in network and multimedia technologies. As a result, copyright infringement

of digital content is also increasing and it is now recognized as a serious problem.

Digital watermarking [1, 2] may be used as an effective method for identifying the

copyright ownership of digital content from unauthorized use and distribution. In

digital watermarking, a watermark which contains the copyright information is

embedded into the digital media content such as images, audio, and video, and may be

extracted when the copyright ownership of the digital content needs to be verified [2,

3]. In the previous researches, many digital watermarking methods have been

Corresponding author

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proposed. There are discrete cosine transform (DCT) [4, 5], DWT [6, 7], singular

value decomposition (SVD) [8], and DFRNT [9] single domain based watermarking

techniques. To complement single transform based watermarking, dual transform

domain based watermarking techniques such as DWT-DCT [10] and DWT-SVD [11]

have also been proposed.

In this paper, we propose an efficient digital image watermarking algorithm based

on the dual transform method which combines DWT and DFRNT domains using 2D

barcode in order to the imperceptibility, security, and robustness of the watermark

against image signal processing and various attack.

2 Proposed Algorithm

2.1 Techniques in Proposed System

In watermark generation process, we use 2D barcodes which have various

information capacities and the self-error correction function and the block code

pattern for encoding a 2D barcode. The process increases the hidden computational

complexity of information. The transform method used in the proposed system

consists of a combination of DWT and DFRNT [12] dual domain in order to ensure

the imperceptibility, security, and robustness of the watermark due to the frequency

decomposition ability of DWT that extracts robust coefficients and the unpredictable

random characteristic of DFRNT.

2.2 Watermarking Process

Fig. 1. Watermark embedding process

The watermark embedding process is summarized as follows: First, we generate the

watermark image through the 2D barcode and block code encoding. Next, the original

host image signal is decomposed into three sub-bands, H, V, and D, through the two-

level 2D-DWT, and DFRNT is performed on the sub-band coefficients. And then, we

embed the watermark image into the sub-band coefficient value using quantization

technique. Finally, we performed the inverse DFRNT (IDFRNT) and inverse DWT

(IDWT) and obtain the watermarked image. Fig. 1 shows steps in the watermark

embedding process. The watermark extraction process is performed in such a way that

the embedding process is inversely applied to the watermarked image signal.

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346

3 Experimental results

In order to evaluate the performance of our proposed algorithm, we have performed

the experiments with respect to the imperceptibility and robustness of the watermark

in various conditions including compression and noise adding attacks.

We used a 512512 standard gray level image of size as the sample host image and

a 2121 cell QR code, and 22 block code encoder. While 2D-DWT is performed, the

image signal is scanned in 88 block unit. In order to evaluate the imperceptibility

and robustness, we compute the peak signal to noise ratio (PSNR) and Bit Error Rate

(BER). BER value is calculated as follows:

(1)

(a) Original image (b) Watermarked image

Fig. 2. Image signals before and after embedding watermark.

The comparison of the original image with the watermarked image without being

attacked is shown in Fig. 2. The value of the quantization coefficient Q value was set

to 25 and the acquired PSNR is 40.01 dB.

Table 1. Experimental results by various attacks.

Attack type Compression Gaussian noise

Watermark

BER=7.48% BER=17.6%

QR Code

BER=0.09% BER=1.84%

We performed the experiments by carrying out compression and noise adding attacks,

and the extracted watermarked image and restored QR code after being attacked are

shown in Table 1. In the case of compression attack, JPEG Quality Factor (QF) was

set to 65. In the case of Gaussian noise attack, mean was set to 0 and variance was set

An Efficient Image Watermarking Scheme based on DWT-DFRNT Dual Transform Method for Digital Content Protection

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to 0.001. The experimental results verify that the proposed algorithm ensures the

imperceptibility and robustness of the watermark.

4 Conclusions

In this paper, we have proposed an efficient image watermarking scheme based on

DWT-DFRNT dual transform method for Digital Content Protection. We used a 2D

barcode which contains watermark information and the block code encoder to

generate watermarks. We performed various experiments to evaluate the performance

of the proposed algorithm. The experimental results presented that the proposed

algorithm has good imperceptibility and ensure robustness of watermark against

image compression and Gaussian noise attacks.

Acknowledgments. This research project was supported by the National Natural

Science Foundation of China (Grant No. 61262090).

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