US 11,983,789 B1
Generation method, detection method, generation device, and detection device of zero watermarking for trajectory data, and storage medium
Na Ren, Nanjing (CN); Changqing Zhu, Nanjing (CN); Yuchen Hu, Nanjing (CN); Qianwen Zhou, Huai'an (CN); and Heyan Wang, Baoding (CN)
Assigned to NANJING NORMAL UNIVERSITY, Nanjing (CN)
Filed by Nanjing Normal University, Nanjing (CN)
Filed on Jan. 13, 2024, as Appl. No. 18/412,497.
Claims priority of application No. 202311041918.6 (CN), filed on Aug. 18, 2023.
Int. Cl. G06T 1/00 (2006.01); G06F 21/16 (2013.01); G06F 21/60 (2013.01)
CPC G06T 1/0064 (2013.01) [G06F 21/16 (2013.01); G06F 21/602 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A generation method of zero watermarking for trajectory data, comprising:
generating copyright information;
compressing a trajectory T composed of trajectory data, thereby obtaining a compressed trajectory Tdp and a compressed trajectory Ttdtr, wherein a Euclidean distance threshold and a maximum synchronous Euclidean distance threshold are keys for compressing the trajectory T;
deleting starting points in the compressed trajectory Tdp and the compressed trajectory Ttdtr, and taking an intersection of the compressed trajectory Tdp and the compressed trajectory Ttdtr after deleting the starting points to obtain a trajectory T′;
calculating a minimum area bounding rectangle of the trajectory T′, and taking midpoints of four sides of the minimum area bounding rectangle to divide the trajectory T′ into four equal parts;
counting the number of trajectory feature points in each of the four equal parts, selecting a vertex of the minimum area bounding rectangle in one of the four equal parts with the highest number of trajectory feature points as an origin, taking a longer side of the minimum area bounding rectangle connected to the vertex as an X-axis, taking a shorter side of the minimum area bounding rectangle connected to the vertex as a Y-axis, thereby constructing a rectangular coordinate system;
taking ω as a key and dividing the trajectory T′ into ω×ω child trajectories based on the rectangular coordinate system, wherein each of the child trajectories has a child trajectory index (childx, childy);
taking ε as a key and dividing each of the child trajectories into ε×ε child blocks, traversing each of the child blocks, assigning a value of 1 to each of the child blocks containing at least one of the trajectory feature points, assigning a value of 0 to each of the child blocks without any one of the trajectory feature points, and obtaining a binary image PB having ε×ε pixels of each of the child trajectories based on assignment results of the child blocks;
acquiring a row index xi and a column index yi of each of pixels assigned with the value of 1 in the binary image PB, taking the row index xi and the column index yi as variables to calculate a linear invariant moment, thereby obtaining seven moment invariants I(I1, I2, I3, I4, I5, I6, I7);
quantifying the four moment invariants I1, I2, I3, and I4 to 0 or 1, and then splicing the quantified moment invariants to obtain a binary sequence M with a length of 4;
calculating an average value subx of row indexes and an average value suby of column indexes of the pixels assigned with the value of 1 in the binary image PB; sequentially splicing the average value subx and the average value suby with the child trajectory index (childx, childy) and a corresponding trajectory number id in that order, and using a hash function to calculate a watermark index Windex;
mapping the binary sequence M to positions [1, N] based on the watermark index Windex, selecting and combining each bit on the mapped binary sequence to form a combined binary sequence, and then combining watermark bits of the combined binary sequence to define a zero watermarking sequence Watermarkbit with a length of N; and
obtaining copyright watermark information CopyrightInfor based on the zero watermarking sequence Watermarkbit and the copyright information.