Research On Application Of Digital Watermark In Variable Data Printing

Digital watermark technology, developed in recent years, is one of the effective means to implement copyright protection and information security. This paper combines variable data printing with digital watermark technology research, studies the application of the digital watermark in variable data printing. On the one hand, digital watermark is applied to actual, on the other hand, it uses the digital watermark technology enables variable data document with security information, which not only can effectively protect users'interests, also can prove file of authenticity sex, and meet the needs of the users.The main research contents of paper come up with an optimization digital watermark anti-counterfeiting algorithm based on wavelet transform, and apply it to variable data printing. Variable data document contains variable image and variable text. This article using software module extracts the text from the variable data document, and puts the text as the watermark information, then embeds it to variable image, makes the variable data document contain a digital watermark information, so as to achieve the purpose of security.This paper solves the two key problems:one is to study the variable data document structure and tags, ensure the images which are embedded watermark can be properly invoked. Two is to optimize the watermark embedding and extracting algorithms, strengthen the robustness of watermark, and ensure that the watermark can be extracted after the output and scanning process. While embedding, the wavelet coefficients ared separated into low frequency coefficients, intermediate frequency coefficients and high frequency coefficients, the watermark information is embedded repeatedly. And while extracting, the scanning images first pass the pretreatment, and then to be extracted. Experiments show that the process of repeatedly embedding and pretreatment can greatly increase the effectiveness of watermark extraction. Meanwhile, the proposed watermark algorithm has a good invisibility and can be extracted in some images with a variety of contents, and has good robustness to noise attack, shear attack and compression attacks.This paper has the following innovation points:①For the first time, it combines variable data document and digital watermark techniques, writes the software modules, which can extracted variable text as watermark information to embed it in variable image.②While embedding, the wavelet coefficients are categorized into low frequency coefficients, intermediate frequency coefficients and high frequency coefficients, according to the different eyes'sensitivity to the three sorts of coefficients, embedded different intensity of watermark, ensure watermark has a good invisibility, and the same time increase the intensity.③While extracting, the scan image go through the process of pretreatment, decrease image distortion caused by printing scanning the degree, greatly improved to the correctness of the extracted watermark.At present, the application of variable data printing embodies in some securities, invoice and personalized product, so this paper research can help the variable data products add security information, make its have anti-counterfeiting function, so as to protect the lawful rights and interests of the owners. Therefore, this research results have certain application value.