| With the increasing popularity of the Internet,more and more multimedia data has been shared through the network.People can use the network to easily achieve information transmission,but also through the network to find the information they want.While the Internet brings convenience to people,a serious problem has been generated.Some criminals steal or tamper with the multimedia data shared on the network for their own interests.The copyright protection problem of digital multimedia is becoming increasingly prominent.Aiming at the infringement problem of color images in complex network environment,a new method of information hiding,digital watermarking technology,was born.Based on the mathematical theory of Hadamard transform,this thesis discusses,designs,and implements a variety of digital watermarking algorithms to improve the performance of the algorithms step by step by taking color digital images as the research object.The main research contents of this thesis are as follows:(1)Analyze the specific process of Hadamard transform,explore the relationship between the coefficients of transform domain,achieve watermark embedding by fine-tuning the high correlation coefficient of transform domain,and then determine the watermark information according to the size relationship between the coefficient pairs containing watermark.In this algorithm,color digital watermark image,which presents the copyright information,can be embedded into the color host image.The watermark information is large and the watermark capacity is high.(2)Observe the distribution law of transformation domain coefficients,find multiple pairs of high correlation coefficients,design and implement the minority obedience to the majority voting system,achieve multiple embedding and extraction of watermark,so that the algorithm has a certain fault tolerance rate to improve the robustness.In addition,the algorithm combined with the variable step size of the color channel,which can ensure the invisibility of the watermark.(3)Make full use of the energy aggregation characteristics of the multistage Hadamard transform,concentrate the energy of the image block twice,get the maximum energy coefficient in the upper left corner,and combine the quantization index modulation technology to complete the watermark embedding.Then,according to the threshold range of the watermark coefficient,blind extraction can be realized.This algorithm only changes one transform domain coefficient,and the value of this coefficient is large,which increases the threshold range and fault tolerance rate,and further improves the invisibility and robustness.(4)According to the rule of matrix multiplication,the calculation of the special transform-domain coefficient in spatial domain are concluded,and the watermark embedding process of transform domain is simulated in spatial domain,so as to avoid complex matrix transformation and reduce the running time to a great extent.Meanwhile,the asymmetric encryption of parameters and keys is realized by combining elliptic curve cryptography to make the algorithm have higher security.Based on the above research,this thesis analyses and designs the dual-color digital image blind watermarking algorithm for color host image and color watermark image by parallel research methods of theory and experiment,and gradually forms a new digital watermarking algorithm with good visual effect,strong robustness and high efficiency and high security by constantly improving embedding and extraction strategies as well as various pre-processing and post-processing processes.It solves the problems of poor security,long running time and difficult to balance the performance of the existing digital watermarking algorithm,and provides an effective method for protecting the image copyright,which has certain academic value and application value. |
