Digital Watermarking Algorithm For Halftone Image

Since its emergence ten years ago, digital watermarking has been widely used in areas such as copyright protection, piracy tracing, copy control and image authentication, and more and more researchers have paid their interests in it. In this thesis, we mainly focus on watermarking into halftone images research.According to the current situation of the information hiding in printed materials, the affect in printing and scanning to image are discussed in the first, the possible lose and distort of information in the print and scan processing are analyzed; based that, two information hiding methods which are both based DCT in printed materials are showed in the second, use the algorithm of scrambling(As the basic means for hiding huge image information, the scrambling of digital image makes the old image to a new disorderly image with a reversible transform), the watermark signal are imbedded to a grey image, after printed with a high resolution ratio, the carrier image is scanned in the same resolution ratio. We use Photoshop to make the scanned image geometic rotation and recovery the original size, then the watermark image is extracted; The experiment show that, the image which extracted in the two methods are better, the experiment indicates that the two information hiding methods in this paper can be used in printed materials copyright protection.