Halftone Reversible Watermarking For Color Images

In recent years,people's awareness of safety has been continuously improved,and digital watermarking technology has been increasingly applied to multimedia security applications.So far,a variety of digital watermarking algorithms have been proposed,which have received much attention in many fields.In recent years,the application of digital multimedia technology has become more and more extensive,and the combination of mature halftone technology and reversible watermarking technology has become a new research hotspot.In the reversible watermarking technique,people can use this technique to extract watermark information from the carrier image,and can recover the carrier image completely.After literature review and experimental exploration,we found the following problems in existing reversible watermarking algorithms:(1)Many algorithms use grayscale images as the original carrier image,but less reversible watermarking algorithms are designed for color images;(2)In existing algorithms,the amount of information that can be embedded is low.After expounding the related research background of halftone and digital watermarking technology,this thesis introduces the existing halftone reversible watermarking algorithms and analyzes the defects of the halftone reversible watermarking algorithms.Next,for the first problem,we use the color halftone image as the original carrier image and propose a color halftone reversible watermarking algorithm.The color halftone reversible watermarking algorithm divides a color halftone image into three channels.Watermark information is embedded in each of the three channels.At the receiving end,watermark extraction is also performed for each channel.The algorithm can not only extract the hidden information completely,but also recover the original carrier image without distortion.For the second problem,we separately calculate the redundant information in the three components of the color halftone image,and select the pattern block that conforms to the standard as the candidate pattern block according to the characteristics of the redundant information.Because the same pattern block may appear in each component,the pattern blocks that appear repeatedly when the look-up table is constructed need only to be selected once.Thus,the redundant information in the three components of the color halftone is statistically generated to generate a look-up table.When the look-up table is embedded into the carrier image,the number of occupied pixel position is reduced,and the amount of embeddable information of the color halftone image is also increased.Finally,in order to verify the algorithm,the experiments of embedding payload and look-up table testing are carried out.It is concluded from the experimental results that,using the proposed color halftone reversible watermarking algorithm,the payload is improved under the fidelity constraint.