Proposes a blind robust image watermarking algorithm based on DWT and DCT. Firstly, the binary meaningful watermark image is preprocessed by Arnold scrambling and logistic chaotic encryption. Secondly, after decomposing the gray cover image into the secondary layer, four bands ( LL2, HL2, LH2, and HH2) are selected to embed watermark. Apply block DCT to each band and employ an improved approach to embed watermark by switching a pair of middle frequency coefficients. The embedding intensity varies with different sub-bands in order to enhance the robustness and realize blind detection. Finally, experimental results show that the algorithm has strong robustness to image adding noise, filtering, cutting, sharpening, JPEG compression, histogram equalization, and other attacks.%文中提出了一种DWT与DCT相结合的灰度图像盲水印算法.该算法首先对二值有意义水印进行Arnold置乱以及logistic混沌加密预处理,其次对灰度载体图像进行二级小波分解,选取逼近子图LL2和细节子图LH2、HL2、HH2嵌入水印.嵌入时对4个子带分别进行分块DCT变换,然后运用改进型相交换中频系数的办法将预处理后的水印分块嵌入4个子带,不同的子带采取不同的嵌人强度,以增强鲁捧性和实现盲提取.实验结果表明,该算法对图像加噪、滤波、剪切、锐化、JPEC压缩、直方图均衡化等攻击有较强的鲁棒性.
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