Research On The Lossless Watermarking Algorithm For STL Model

With the rapid development of computer-aided design and 3D printing technology,as a new type of digital media,3D model has being widely used and its commercial value is tremendous.It is predictably that STL model used as the collaboration between design software and 3D printers will become one of the most common digital goods.Thus,how to effectively protect copyrights and content security of STL models has aroused the common attention from the academia and industry.Digital watermarking for copyright protection and integrity authentication of digital media is an effective technology,and they have broad application prospects for the content protection of STL models.This thesis first introduced the theoretical knowledge of digital watermarking,including its basic concepts,classification and performance evaluation criteria,etc.Then,the watermark characteristics of the mesh model are summarized and the research status of reversible watermarking and entity rearranging techniques are described in detail.Based on the data storage characteristics of STL model and the precision demand in the applications,this thesis mainly research on the lossless watermarking of STL model and the research results were obtained as follows:(1)A lossless watermarking algorithm based on entity rearrangement is proposed.Firstly,the data preprocessing is done to the model by principal component analysis(PCA)method and the reference sequence of triangles in the model is obtained.After that,the triangles and vertices of STL model are reordered by the reference sequence and average coding tree to embed watermark information.Experimental results and analysis show that the proposed algorithm can obtain a large capacity,good fidelity performance,and it is robust against translation,rotation,and even scaling.(2)A lossless watermarking algorithm with high capacity based on the bit mapping and entity rearrangement is put forward.Firstly,the data preprocessing is done to the model by PCA method and the reference sequence of triangles in the model is obtained.Then,in order to improve capacity of the entity rearrangement method,a bit mapping operation is constructed to realize reversible information hiding of bits or decrease the value represented by the successive bits of the hiding data.The capacity of the algorithm exceeds optimal capacity of the standard entity rearrangementmethod and the performance of the fidelity and capacity is very good.In addition,the algorithm has a good time performance,and it is robust against translation,rotation,and even scaling.(3)A lossless watermarking system for STL model is designed and implemented,and it verified the effectiveness of the proposed two lossless watermarking algorithm.The main contribution of this paper is the applications of entity rearrangement technology in STL model,and two lossless watermarking algorithms with high capacity for STL model are proposed.These algorithms have potential application in secret communications,copyright protection and integrity authentication for mesh model.