摘要
为了提高水印的鲁棒性和计算效率,提出了一种基于共轭对称列率复数哈达玛变换的图像水印算法.该算法首先对载体图像分块并进行筛选,找到适合嵌入水印的块;在嵌入之前,根据方差将这些块分成纹理简单和纹理复杂2类,不同类的块使用不同的量化步长,以此来增强水印的鲁棒性;然后,利用量化的方法将经过置乱和扩频的二值水印嵌入到上述块的系数相位中.为了抵抗图像的去同步攻击,提出了一种根据图像变换前后几何矩之间的关系来判断仿射变换的策略,并在此基础上计算变换参数,恢复图像的同步信息.实验结果表明,在满足不可见性的前提下,经历各种攻击之后所提取出的水印仍然清晰可辨,说明该算法具有较好的鲁棒性.同时,所提出的判断策略也能准确地判定载体图像是否经历了去同步攻击以及何种方式攻击.
To improve the robustness and computation efficiency of watermark,a watermarking algorithm based on conjugate symmetric sequency-ordered complex hadamard transform（CS-SCHT） is proposed.In this algorithm,the host image is decomposed into blocks which are selected to find suitable blocks for watermark.Before embedding,the selected blocks are classified into two classes,flat or textured,corresponding to different quantization step for better robustness.Finally,the binary meaningful watermark is embedded into the phases of the blocks by quantization and spread spectrum technique.In order to resist de-synchronization attacks,a strategy to judge affine transformation by relying on the relationship between geometric moments before and after attacks is put forward.The transformation parameters can be computed and then applied to restore the synchronization of the host image.Experimental results show that the extracting watermark suffered attacks is still legible,indicating that the new algorithm has good robustness when transparence is satisfied.Meanwhile,whether the host image suffers de-synchronization attacks existence and what the attacks are can be exactly judged.
出处
《东南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2011年第2期312-316,共5页
Journal of Southeast University：Natural Science Edition
基金
国家自然科学基金资助项目(60873048)
江苏省自然科学基金资助项目(BK2008279)
关键词
共轭对称列率复数哈达玛变换
共轭对称
去同步攻击
仿射变换
检测阈值
conjugate symmetric sequency-ordered complex hadamard transform（CS-SCHT）
conjugate symmetric
de-synchronization attack
affine transformation
detection threshold
