一种双重变换域图像半脆弱水印算法

Semi-fragile watermarking algorithm in dual transform domains

提出了一种DCT域和DWT域相结合的双重变换域半脆弱图像数字水印算法。充分利用了DWT变换提取图像特征方面的优势和DCT变换与JPEG压缩过程结合紧密的特点,使用自行设计的篡改估计函数,有效地实现了篡改检测和篡改定位,而且检测时不需要原始图像。使用密钥控制生成的混沌序列对水印进行加密处理,保证了系统的安全性。实验结果表明,该算法对于JPEG压缩等常规图像处理具有较强的鲁棒性,对于恶意篡改具有高度的敏感性,并且能够准确定位篡改发生的位置。

A semi-fragile image watermarking algorithm is introduced combination of Discrete Cosine Transform（DCT） and Discrete Wavelet Transform（DWT） domains.The algorithm takes advantage of the predominance of extracting image features in DWT and the characteristic that DCT is integration in the procedure of JPEG lossy compression.Tamper detection and tamper localization are realized effectively because of a tamper assessment function is designed and no host image is needed in watermarking extraction.The security of the system is ensured because of a logistic chaos sequence is used for encryptlng the watermarking. Experimental results show that the proposed scheme is robust against normal image operations such as JPEG lossy compression and is high sensitive against intentional tampering.Moreover,it can locate the tampered area exactly.