Research On Revisable Watermark And Multi-Watermark

Digital watermarking technology has a huge rang of application in the field of digital multimedia security. Focusing on the analysis of digital watermark's application in the copyright pretection and the content authentication of digital images, this paper researches both digital reversible watermark and multi-watermark.Based on the existing Pixel Value Mapping Algorithm (PVMA), an improved visible and reversible watermark algorithm for the images' copyright pretection has been proposed in this paper. And the experimental results prove that, with the advantage of controllable visibility, the algorithm overcomes the "noise effect" effectively in the watermarked image; and the watermark and the original image can also be completely erased and restored by the reversible algorithm respectively. Then, based on the existing Extended Difference Expansion Algorithm (EDEA), this paper proposes an invisible reversible watermark algorithm for the images' content authenticationl. Its related experimental results show that, the algorithm not only performs better both in terms of invisibility and embedding capability, but also extracts the watermark successfully by means of revisible algorithm, so that the original image can be restored without distortion.Meanwhile, this paper also does some researches on the multi-watermarks technology which combines the different types of watermark together, including the visible-reversible watermark with the invisible-reversible watermark, and the robust watermark with the visible watermark. And useful conclusion can be reached that, multi-watermarks have complementary functions, which can protects copyright at multi-layers both subjectively and objectively.