Research Of Color Image Watermarking Algorithm Based On Discrete Cosine Transformation

With the advancement of the multimedia technology and rapidly development of the computer network, the digital media has been used more and more widely. Then the problems of information security, intellectual property protection and certification are becoming seriously. Digital watermarking is an effective method to protect digital works'copyright and information security, to embed some digital labels or signatures into multimedia in such a way that it causes no noticeable perceptual distortion to the original data.Although much has been done on digital watermarking in the past few years, many problems remain to be resolved. In this thesis, we research the color digital watermarking algorithm based on discrete cosine transformation to solve the problem of copyright protection of static color images. The main research contents as follows:(1) Base on the frequency sensitivity, brightness sensitivity and contrast masking of human visual system, controlling the embedding strength of digital watermark for each coefficient by JND (Just Noticeable Difference) model. In this way the quality of original image can be avoid more destroying.(2) Embedding watermarking into low, middle and high frequency coefficients of discrete cosine transformation respectively. Experimental results show that the algorithm is hard to keeping imperceptions and robustness while embedding into low and high frequency coefficients. When embedding into middle frequency coefficients, it is imperceptible and robust that can resist many image attacks such as JPEG compression.(3) Embedding watermarking into red, green, blue channel of color image respectively. Experimental results show that watermarking of green channel is more robust with JPEG compression.(4) An algorithm is proposed for color image digital watermarking based on DCT transformation. The original binary watermark image was firstly encrypted through Arnold scrambling technique, and then embedded into DCT middle frequency coefficients of host image green channel. The experiments show that this algorithm is imperceptible and robust.(5) Designed Experimental program under Matlab environment, select different host images to prove imperceptible and robust of the algorithm. The results show that the...