The Design And Implementation Of Digital Watermarking System For Print-and-scan Process

In this thesis, the digital watermarking algorithms for print-and-scan process are studied and effectively applied in the anti-counterfeiting, identification and tracking of the hard-copy images. Through the analysis of these algorithms are reviewed, a more complete system on digital watermarking which can resist to the print-and-scan attacks is designed and implemented.This thesis focuses on analysis of the impact of digital watermarking through the print-and-scan process. The luminance transformation and contrast stretching transfor-mation are applied to adjust the pixel distortion and the Radon transformation is used to adjust the geometric distortion. The experiment results indicated that these methods can remarkablely improve the success rate of the watermark detection.According to the character that symbol of parts of images' DCT coefficient are not changed after the print-and-scan process, a DCT-based system on digital watermarking for the print-and-scan process is designed and implemented in this thesis. The system's input are the original image, watermark image, and the extracted watermark image as the output; What's more, the pre-process module for the image which undergoes the print-and-scan attacks is added to this system in order to adjust the pixel and geometric distortion.The experiment results demonstrated that this system can better resist to the print-and-scan attacks and also had a certain degree of robustness to other common at-tacks.