Reversible watermarking of 2D-vector data

This paper presents a reversible watermarking scheme for the 2D-vector data (point coordinates) which are popularly used in geographical information related applications. This reversible watermarking scheme exploits the high correlation among points in the same polygon in a map and achieves the reversibility of the whole scheme by an 8-point integer DCT, which ensures that the original 2D-vector data can be watermarked during the watermark embedding process and then perfectly restored during the watermark extraction process, with the watermark accurately extracted at the same time.In our scheme, we use an efficient highest frequency coefficient modification technique in the integer DCT domain to modulate the watermark bit "0" or "1", which can be determined during extraction without any additional information to indicate.To alleviate the visual distortion in the watermarked map caused by the coefficient modification, we propose an improved reversible watermarking scheme based on the original coefficient modification technique. Combined with this improved scheme, the embedding capacity can be greatly increased while the watermarking distortion is otherwise deduced compared to the original coefficient modification scheme.To control the distortion between the watermarked 2D-vector data and its original version, we design an error estimation method to prevent those data which are able to cause large distortions in the coefficient modification process from being watermarked. This distortion limitation scheme can fine adjust the watermarking distortion and capacity for the proposed coefficient modification based reversible watermarking scheme according to different practical requirements.