Research On Anti-print And Scan Watermarking Algorithm For Halftone Images

With the rapid development of technology, high precision laser printersand scanners were used widely. The copy of prints become very easy. Thecopyright protection appears particularly important. So the study of theprotection of prints which can contrast print and scan attacks enjoys a veryhigh practical significance.The work principles of printer and scanner were introduced in the paper,and analyses the influence of printer and scanner to the copy of image. Afterfurther research of digital watermark, halftoning and the edge detection, a kindof digital halftone image watermarking algorithm to resist print and scanattacks is proposed, which is based on the edge detection and improved errordiffusion.Watermark is pretreated with Arnold before embedding to improve thesafety of watermark. In order to improve the invisibility of watermark, firstly, theedge of gray image is gotten using canny detection, and the edge of thegray-scale image can be approximately regarded as the edge of the halftoneimage. Secondly, using the noise visibility function to selects the complextexture edge points as the location of the embedded watermark. Thirdly, theerror diffusion algorithm was improved when the gray image halftoning.Experiment results show that the algorithm is good resistance to print and scanattacks, while resistance to shearing, noise and JPEG compression attacks,and has good robustness.