The Research Of Engineering Drawing Digital Watermark

2D engineering drawing is one of the most important carriers of design information. Its copyright protection problem draws many people's attention. This paper studies the digital watermark technology for the 2D engineering drawings graphic files and proposes embedding algorithm, extracting algorithm and printing algorithm of the 2D CAD files in order to offer an effective measure for the engineering drawing copyright protection.According to the characteristic 2D engineering drawing graphic data, this paper proposes a technique which gains redundant information through the random perturbation of the engineering entities. In order to enable randomness to have good statistical property, this paper also quotes a pseudo-random number generator. Then this paper separately introduces the watermark embedding methods of line, circle and polyline which are most commonly used in the 2D engineering drawing .That is gaining redundant information through stochastic perturbation of these entities .And then the digital watermark intensity factor and watermark sequence were operated on redundant information by linearity or non-linear way. We can obtain the good transparency and robustness watermark through the adjustment of intensity factor and the function way.This paper's digital watermark extracting algorithm make use of the digital watermark the non-blind extracting algorithm. It needs the inputs of two 2D engineering drawings one of which has embedded the watermark ,and the other has not. It extracts the watermark sequence from the engineering drawings which has embedded the watermark through the comparison of the entities of these two engineering drawings. In the extracting algorithm, this paper proposes effective methods which resist the entity deletion and increase attack .Finally the random number is used to produce watermark sequence to determine the biggest threshold value in order to obtain the determination threshold value .The existence of the watermark is judged through the determination threshold value.According to the Windows2000 the printer driver system structure and the printing flow, this paper proposes a watermark printing algorithm which embeds the watermark background using the printer driver. Firstly, extract the watermark sequence which has embedded in the engineering drawing using the extracting algorithm above. Then using the inverse function which can generate the watermark sequence, the watermark sequence is reverted to the enterprise information, and then the printing device is initialized. After the initialization, it can append the enterprise information to the engineering drawings as watermark background. This technique can play the warning and stating copyright information role and have good versatility and usability.Under Visual C++6.0 development environment, this paper realizes the embedding algorithm and the extracting algorithm of the 2D engineering drawings using OpenDWG Toolkit. The experimental result indicates that these two techniques have good robustness for the geometry attack, such as translation, revolve, scale, deletion and increase .And determine the determination threshold value of the embedding algorithm and the extracting algorithm. Also under Visual C++6.0 development environment, realize the printing algorithm of the 2D engineering drawings using the Windows DDK. The example proves that this technique has the good effect.The research on the digital watermark technology of the 2D engineering drawing is just at the very beginning. The robustness of this technology needs to be strengthened. Moreover, the union of the digital watermark technology and the encryption technology will be a better solution for enterprise information security problem.