Research On The Technology Of Digital Watermarking Based On Halftone Image

Digital watermarking is a very convenient and effective method for anti-counterfeiting of digital products.It has good imperceptibility and robustness and is widely used in digital media information copyright authentintication.With the development of media technologies,halftone images are transmitted in large amounts in the Internet.Howver,the digital watermarking technology for halftone images cannot fully meet the requirements of copright protection.Therefore,it is necessary to propose a digital watermarking technology based on halftone images.Through the comprehensive analysis of the application of digital watermarking technology in the field of continuous and halftone images,the w atermark is embedded and extracted in the space domain.Combined with the human visual model theory,the problem of poor visual quality of the image after embedding the watermark information in the halftone image is improved,and the watermark is embedded and extracted using similar pixel block replacement.The human eye visual characteristic matrix is convoluted with the original pixel block matrix and the alternative pixel block matrix respectively.The Euclidean distance is used to calculate the minimum distance between the alternative pixel blocks with the original pixel block,and establish a lookup table.The halftone image with watermark by this method has good visual quality,PSNR is above 48.0000,and watermark concealment is strong.The results show that a reversible watermarking algorithm is implemented in the way of similar pixel block flipping,which can not only be used for copyright certification but also restore carrier information for content protection.Since the lookup table is also embedded in the carrier image,the watermark can be extracted blindly.The watermarking method is programmed in Matlab software and the watermark recognition degree is evaluated by normalized correlation coefficient NC.Attacks on images by cutting,modifying and the salt and pepper noise:When the attack is weak,the watermark NC value is larger,above 0.80,the recognition degree is high;when the attack is strong,the NC value can reach above 0.65,with certain The degree of recognition.The watermarking method has good robustness and can also be used for anti-counterfeiting and copyright protection of halftone images.