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The rapid development in information science and technology has brought great changes to the whole society. It becomes more and more intelligent, especially when the mobile smart devices appear, which expands the range of applications of the Internet greatly. However, for the portability considerations, the input of mobile smart devices is limited. The input is extremely inconvenient when using a mobile device to access the Internet via wireless networks. The Quick Response Code (QR Code) makes the quick access of information, such as the URL, possible. The intelligent mobile devices can conveniently access the information through scanning and decoding the QR Code, which breaks the input limitations. Visually, the QR Code is a two-dimensional binary image of black and white pixels. However, it is not random but follows some certain coding rules. As an extension of the one-dimensional bar codes, the QR Code is intended to increase the shortage the bar code to achieve more applications. The QR Code has a higher capacity, a stronger error correction capability and a higher reliability in encoding and decoding compared with the one-dimensional bar code.
Digital watermarking technology can protect the digital media and realize the copyright authentication by embedding additional information into the digital media. It can be sorted according to different criteria. Based on the visibility, they are invisible watermarks (Alattar, 2004; Chang, Lin, & Fan, 2008; Hu & Jeon, 2006; H.-C. Huang, Chang, & Fang, 2011; Kim, Lee, Lee, & Lee, 2009; Ni, Shi, Ansari, & Su, 2006; Tai, Yeh, & Chang, 2009; Tian, 2003; P. Tsai, Hu, & Yeh, 2009; Yang & Tsai, 2010; Zhao, Luo, Lu, & Pan, 2011), and visible watermarks (B.-B. Huang & Tang, 2006; Liu & Tsai, 2010; H.-M. Tsai & Chang, 2010). Based on the reversibility, they are reversible watermarks and irreversible watermarks. Based on the ability of resisting attacks, they are robust watermarks, fragile watermarks, etc.
The QR Code as visible watermark damages original image in some degree, which limits the application scenario of QR Code. There are scenarios that require absolute precision of original image, such as the military images, the medical images, and so on. Therefore, reversible recovery of original image is very important. This paper presents a reversible visible watermarking scheme, which embeds the QR Code as the visible watermark. The QR Code is embedded as the visible watermark into the image through an adaptive MSB (Most Significant Bit) substitution method, which considers the features in the coding and decoding process of QR Code. Then all the changes caused by the visible watermark are recorded and invisibly embedded into the watermarked image by a reversibly data hiding scheme. The proposed scheme can realize all the applications combining with QR Code. Besides, the QR Code can be removed and the original image can be recovered reversibly. Due to the adaptive visible watermarking and the reversible data hiding with high capacity, the proposed scheme achieves better results compared with existing schemes.