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

Introduction

Recently, reversible watermarking has attracted much attention from the researchers working in the field of multimedia security. Because it allows perfect recovery of the original content of the host media after the watermark is extracted, it has found potential applications in the area of medicine, justice and military, where integrity and authenticity is of paramount importance. Since the conception of reversible watermarking 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 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.