A New Gray-scale Watermarking Scheme Based On Irregular LDPC Codes With Unequal Error Protection

In recent years,the rapid development of Internet technology not only brought convenience to people's lives,but also brought a lot of issues such as copyright disputes,piracy and other issues.With the emergence of these problems,digital watermarking technology for these problems emerges as the times require.The main problem of the digital watermarking technology is how to resist various malicious attacks and to achieve the tradeoff between invisibility and robustness.In view of the above problems,we focused on the invisibility of the watermark embedded into carrier and the robustness of the watermark.We mainly study the digital watermarking method based on the irregular low-density parity-check(LDPC)codes with unequal error protection(UEP)in this paper.For the invisibility of watermark,we combine the discrete wavelet transform(DWT)with singular value decomposition(SVD)to embed digital watermark.Discrete wavelet transform is part of the transform domain decomposition,the carrier is decomposed into the original multi-bands.It is able to adapt to the visual characteristics of the human eyes while allowing the multiple-level embedding.It has both advantages of Time-space method and discrete cosine transform method.Singular value decomposition has considerable stability,while the singular value reflects the inherent characteristics of the original carrier,the change of singular value can not cause large visual changes.It will improve the imperceptibility of the digital watermarking.This combination of the both methods enhanced digital watermarking invisibility.For low robustness of digital watermarking,we encode digital watermarking with irregular LDPC codes with inherent UEP property to enhance the ability to resist malicious attacks.We can take the digital watermarking system as a digital communication system,error correction coding for digital watermarking can improve the reliability of the watermark transmission in channel.We take gray-scale image as the original digital watermarking,decompose the gray-scale image into bit planes,so there exists the most significant bit plane,the second important plane and the least bit planes.Absolutely,it is unreasonable to treat all the bit planes equally.Therefore,in this paper,we present a new watermark method based on irregular LDPC with inherent UEP features.The most significant bits protect the most important bit planes,the less important bits protect sub significant bit planes,thus the robustness of digital watermarking can be enhanced significantly.In this paper,we do detailed experiments for the proposed algorithm,and compare the extracted watermarking images.The PSNR of loaded carrier is 40.2dB in the digital watermarking scheme proposed in this paper,it shows that the digital watermarking in the proposed scheme has good imperceptibility.The PSNR of extracted watermarking reaches 40 dB under the Gaussian noise attack with variance of 0.7,0.8 and 0.9,it shows that the proposed watermarking scheme has strong robustness.