DCT域半易损水印技术

该文提出了一种DCT域半易损水印技术用于图像内容认证．水印嵌入算法基于DCT域的JPEG压缩不变特性，对一定质量的JPEG压缩是稳健的．水印比特包括认证比特和恢复比特．认证比特是块自嵌入的。可以对不可接受的图像篡改进行准确的检测和定位，而恢复比特则可以对篡改的图像进行一定程度的恢复．该文还分析了DCT变换过程中取整误差的影响，从理论上证明了水印嵌入算法中迭代过程的收敛性．实验结果证明了该半易损水印可以容许一定程度的JPEG压缩和AWGN噪声，对局部发生的篡改可以有效地检测、精确定位并进行内容恢复．

DCT Based Semi-Fragile Watermarking Technique

This paper introduces a DCT based semi-fragile watermarking for image content authentication. The embedding algorithm is based on some invariant properties in JPEG compression to get robustness against JPEG compression. The watermark includes authentication bits and recover bits. The authentication bits are block self-embedded and have the ability of detecting and localizing unacceptable tamper in image, while the recover bits are used to reconstruct the tampered area approximately. The impact of integer rounding error is analyzed,and the convergence of iteration process is demonstrated. The experimental results demonstrates that the proposed algorithm can tolerate the distortion under certain JPEG compression and AWGN, and can effectively detect, localize and restore the tampered area.