An Effective Reversible Watermarking for 2D CAD Engineering Graphics Based on Improved QIM

Quantization index modulation (QIM) is widely used in watermarking, but QIM cannot be applied to reversible watermarking directly due to its inherent limitations. In this paper, an improvement is made to QIM to make it suitable for reversible watermarking. Based on the improved QIM (IQIM), a reversible watermarking scheme for 2D CAD engineering graphics is proposed. The relative amplitudes and the relative phases of entity vertices are used as hosts to carry the watermark, respectively, and the data recovery is controlled by a secret key. Experimental results indicate that the proposed scheme can strike a good balance between capacity, imperceptibility, robustness, security and complexity. was firstly introduced by Honsinger et al. (1999), many works have been done on this topic. Currently, researches on reversible watermarking are mainly focused on raster images, while little work has been done on vector graphics watermarking. Vector graphics are widely used in geographical information systems (GIS), computer aided design (CAD) and animation. 2D CAD engineering graphics is a typical kind of vector graphics, and has been intensively applied in construction, mechanism and costume design. In most application cases, high precision of the graphics is one of the most important requirements; therefore if watermarking is to be used for authentication DOI: 10.4018/jdcf.2011010104 54 International Journal of Digital Crime and Forensics, 3(1), 53-69, January-March 2011 Copyright © 2011, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. purpose, reversibility of the original graphics after watermark extraction is desirable. Chen and Wornell (1998, 2000, 2007) proposed a few watermarking algorithms based on QIM. They have proved that QIM based embedding can strike a good balance between capacity, invisibility and robustness. However, these schemes are not reversible, which limits its application in 2D CAD engineering graphics. In this work, we propose an improved version of QIM IQIM and use it to construct a reversible watermarking scheme for 2D CAD engineering graphics.