Research Of Digital Watermarking Technique In Transform Domain

With the rapid development of computers and networks, digital media products to work and life, while convenient, it also brings security, and other copyright issues. Digital watermarking is an effective method for copyright protection of digital information, received extensive attention:Based on the analysis of the existing digital watermarking technique based on the proposed two digital image watermarking algorithm:(1)Digital watermarking Algorithm Based on SVD in DCT domain. Firstly, Original image was divided into blocks and their entropy and standard deviation were calculated. According to HVS characteristics, selected some blocks with larger entropy and smaller standard deviation to embed watermark. Selected blocks are transformed into DCT domain and then operating SVD. The binary watermark image was embedded into the S component of those SVD decomposition after encrypted by chaotic encryption. Due to the watermark was embedded three times, the amount of embedded information is increased. Watermark obtained by selecting best one from three watermarks extracted from watermarked image. The experiment results show the algorithm has good invisibility and robustness to JPEG compression, image add noise, median filtering, cropping and other image processing operations.(2)Zero-watermark Algorithm Based on Image Normalization. A new zero-watermark algorithm is proposed, combining with image normalization techniques. Firstly, the image normalization techniques are used in the original image to extract a significant-region and transform it by using DWT(Discrete Wavelet Transform), then select its low frequency sub bands to block DCT(Discrete Cosine Transform). Matrix composed by direct current component coefficients of each block extracted by determining the average relationship of low-frequency coefficients and the matrix of each block. Finally, combining with the copyright watermark to produce zero-watermark. Experimental results show that algorithm had good robustness to common image processing and resist geometric transformation.