空间域与频率域相结合的抗图像处理全息水印

Holographic watermarking for anti-image processing based on spatial and frequency domains

为了解决数字全息水印技术无法抵抗图像处理攻击的问题,采用共轭对称延拓生成低噪声加密全息水印图像,嵌入水印时采用频率域的离散余弦变换(DCT)与空间域的拉普拉斯金字塔变换方法相结合。首先,对水印图像进行傅立叶共轭对称延拓生成低噪声的双随机加密全息水印,对宿主图像进行拉普拉斯金字塔分解,提取拉普拉斯金字塔第1层残差图像;然后,通过DCT,将加密水印替换其中高频域后逆DCT;最后,嵌入水印信息后的第1层拉普拉斯残差图像与其他残差图像重构成含水印图像。实验结果表明,含水印图像的峰值信噪比(PSNR)值达到35.7dB,细节损失少,提取水印图像人眼可清晰分辨水印内容,且在满足不可见性的同时可以抵抗常见的图像处理攻击,保证了水印信息鲁棒性与安全性的要求,能够应用于实际生产中。

In order to solve the problem that the technology of digital holographic watermarking can not resist the attack of image processing,the low-noise holographic watermark image which is encrypted by the conjugate symmetry extension,and the watermark is by combining discrete cosine transform（DCT）in frequency domain with the Laplacian Pyramid transform in the spatial domain.Firstly,handle the watermark image by Fourier conjugate symmetry extension in order to generate the low-noise double random encryption holographic watermark.Then,decompose the host image by Laplacian pyramid,and extract the first layer residual image of Laplacian pyramid.Next,embed the watermark which is encrypted into the high frequency domain of host image by DCT transform.Finally,restructure the first layer Laplacian residual image that is embedded with the watermark image and other residual images to get the image containing watermark.The experimental results show that not only the PSNRvalue of the watermark image can reach 35.7dB,but also the human′s eye can clearly distinguish the watermark content.It can satisfy the imperceptibility very well,at the same time,can resist common attacks about image processing,and ensure the robustness and security,so it can be used in the practical production very well.