Tickets are tickets for watching the Olympics, concerts, and attending advanced conferences. With the development of high-quality image input and output devices, especially the emergence of color inkjets, laser printers and high-precision color copiers with an accuracy of more than 1,200 dpi, the forgery of tickets has become easier. Therefore, people urgently need an effective ticket anti-counterfeiting and detection technology. The traditional anti-counterfeiting technology basically adopts material anti-counterfeiting and belongs to common anti-counterfeiting. If it is counterfeited, the consequences are unimaginable, and there are also shortcomings such as high cost. The digital watermarking technology belongs to the personalized anti-counterfeiting technology. It combines with the personality characteristics, does not change the mature printing process, does not change the printing materials and equipment, does not increase the printing cost, and is currently a good anti-counterfeiting technology.
1 Anti-counterfeiting detection system overviewAnti-counterfeiting system overview
A watermark is an operational behavior in which information is not intentionally embedded in a work. Digital watermarking is a mark (watermark) with a specific meaning, which is hidden in digital products such as digital images, sounds, documents, books, videos, etc. by means of digital embedding to prove the creator's ownership of his works, and at the same time through the watermark The detection and analysis guarantees the complete reliability of digital information. Digital watermarking is an emerging and effective digital product copyright protection and data security maintenance technology. The use of digital watermarking technology in the imitation of printed matter is a new direction of research in recent years.
The digital watermark ticket anti-counterfeiting system consists of two parts: a digital watermark embedding subsystem and a digital watermark recognition subsystem. Each subsystem is composed of hardware and software. The user can insert the digital watermark key in the printed matter of the ticket that cannot be perceived by the naked eye and does not affect the original visual sensory image of the protected printed matter, and the digital watermark is read by a unique detecting device, a machine-readable device. In order to identify the authenticity of the printed matter, so as to achieve the purpose of anti-counterfeiting.
This paper introduces the embedding of digital watermarks in tickets, and describes the hardware and software in the watermark identification system in detail. The hardware consists of a camera, an ARM, a liquid crystal panel, and the like.
The entire system flow is shown in Figure 1.
1.2 digital watermark embeddingAs far as the current ticket usage is concerned, it is mainly for printing (or printing) scanning (or photography) operations, so we are looking for an anti-printing scanning digital watermarking algorithm. The algorithms that can be used for imitation of printed matter are mostly implemented in the transform domain, and the ideas are mostly based on the cooperative communication algorithm proposed by J. Coxdeng et al.
This paper will use the DCT (Discrete Cosine Transform) algorithm to embed watermarks. The discrete cosine transform belongs to one of the orthogonal transform image coding methods. For a typical image, after conversion, most of the DCT energy in the image will be concentrated in the DC coefficient and the low frequency AC coefficient. Many AC and high frequency AC coefficients are close to each other, and removing them will not significantly affect the reconstructed image. the quality of. This paper completes the watermark embedding by DCT transforming the ticket image, combining the human visual characteristics and appropriately changing the value of a certain intermediate frequency coefficient. When the watermark is extracted, it is only necessary to judge the positive and negative of the corresponding intermediate frequency coefficient to recover the watermark image. Experiments show that the algorithm is simple and effective against print scanning.
The pictures before and after the watermark embedding and the embedded information are shown in Figures 2 to 4.
The authenticity detection of the ticket embedded in the watermark needs to be discerned by a special machine-readable device. The device is mainly composed of three parts: operating system customization, image acquisition and image digital watermark detection. The core chip of the system uses the S3C2410 embedded microprocessor produced by SAMSUNG Semiconductor. The software environment uses the Microsoft Windows CE.NET operating system. The system first collects the static picture of the ticket through the USB camera, and then performs digital watermark detection and extraction. By comparing the extracted digital watermark with the originally embedded watermark, the authenticity of the ticket is judged.
2.1 Customization of the operating systemEmbedded system refers to application-centric, computer-based technology, software and hardware can be tailored, adapt to the specific application system for functional, reliability, cost, size, power consumption and other strict requirements of the embedded system with real-time Characteristics such as sex, its application prospects are very broad.
The system hardware platform uses the embedded development platform UP_NETARM2410_S of Borch Technology. The platform uses the S3C2410X microprocessor. The processor was developed using the ARM920T core, a 0.18μm process CMOS standard macrocell, and a memory compiler. Its low power consumption and excellent all-static design are ideal for cost and power sensitive applications. The platform is also equipped with an LCD screen for easy observation of watermark results.
Windows CE is an embedded operating system with preemptive multitasking capabilities and powerful communication capabilities. It is also a new operating system designed by Microsoft for non-PC fields such as mobile devices and consumer electronics and embedded applications. Advanced modularity, good real-time performance, powerful communication capabilities, support for multiple CPUs and more. Windows CE uses a user-friendly interface that looks a lot like the popular Windows NT interface, greatly reducing the difficulty for users. At the same time, its modular design allows system developers and application developers to customize it for a wide variety of products. Windows CE modules and components can be selected, combined and configured to create a user-defined operating system.
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