一种基于分块DCT的混沌半脆弱图像水印技术*

提出了一种用于数字图像内容认证的半脆弱水印方案。将图像进行分块，图像块的归一化标准差经量化操作后映射为混沌系统初值，经混沌映射生成水印比特。用量化系数技术将水印比特嵌入块DCT直流系数。利用混沌对初值极端敏感性的特点,能够定位检测对加入水印图像的窜改,并且水印提取不需要原始图像。实验结果表明，嵌入水印后图像的视觉质量好；算法具有对图像内容局部窜改检测的有效性、敏感性以及良好的窜改定位能力，并具有更好的抗JPEG压缩、加性高斯噪声和中值滤波的鲁棒性。

Chaotic Semi Fragile Image Watermarking Based on Block DCT

A new chaotic semi-fragile watermarking scheme for image content authentication is presented.An image is splitted into many non-overlapping blocks,and DCT is performed in a block.The normalized standard variances of the block through quantization processing,and map the initial values of the chaotic mapping.The warermark obtained by iterating several times of the chaotic mapping,is embedded into the DCT DC coefficient with quantization technique.The proposed scheme is exploiting the high sensitivity on initial value of chaotic map,can localize the tampers on the watermarked image.Moreover,no host image is needed in watermark detection.The simulation results show that,the watermarked image has high quality,the proposed scheme has effectiveness,sensitivity and localization of tamper-proofing,but more robust to JPEG compression,some degree AWGN and mean filter.