A map data watermarking using the generalized square mask

This paper presents an algorithm of watermark insertion and extraction on a vector image such as map data. Most parts of the vector image such as map data consists of an array of coordinate values. At first, the image is partitioned into blocks with the same area and every vertex coordinate value within a block is changed to a new coordinate value whose origin is at the south-west vertex of the mask belongs to the associated block. According to the value of the watermark, the insertion area is different. Unlike the work by Sakamoto et al (2000), the authors may be able to use an arbitrary size of the square mask. The mask of the Sakamoto et al.´s work is specific since the length of the mask is 2^R-1 where R=1, 2, …, n. The authors also show that their method is superior to the previous work against noise attack