Reversible Watermarking of SVG Graphics

Reversible watermarking is suitable for hiding data in 2D vector graphics, especially in scalable vector graphics (SVG) medical images, because it can remove the distortions induced by watermark embedding after extracting the hidden bits. This paper proposes a novel reversible watermarking scheme based on the difference expansion and difference shifting. Since the ´path data´ in SVG files includes a sequence of line segments and Bezier segments, we embed the watermark into the vertex coordinates of ´path data´ by modifying the differences between the adjacent vertex coordinates. The scheme can keep the Bezier segments C⁰ continuous by unchanging their start points and end points, and need record neither the location map nor the original least significant bit (LSB) of difference. Our experiment results show that the proposed scheme achieves good performance of the imperceptibility and high-capacity data embedding.