一种结合SPIHT编码的自嵌入水印算法

针对当前基于DCT(离散余弦变换）的自嵌入水印算法对恢复图像细节能力不足的问题，提出了一种基于小波域内嵌编码的自嵌入水印算法。小波变换克服了DCT在图像压缩中的局限性，SPIHT编码则利用了小波变换系数的特性，提高了压缩性能，在同等的嵌入容量时，使水印含有更多图像信息，从而在保证水印透明性的前提下，较传统方法提高了图像恢复质量。同时，鉴于SPIHT算法为内嵌编码，可根据需要调节水印大小从而改变嵌入强度，这也是传统方法所不具备的。Logistic和Cat双重混沌映射的应用，提高了水印安全性和水印检测的能力。最后，进行了算法性能测试实验，验证了本文算法的有效性。

A Self-Embedding Watermarking Algorithm Based on SPIHT Coding

Considering the problem that the current self-embedding watermarking algorithms are insufficient on detail-preserving, an integer wavelet transform combined with SPIHT algorithm is employed to implement a self-embedding watermarking algorithm for image content authentication. Wavelet transform can overcome the defect of Discrete Cosine Transform on image compression. And the characteristic of wavelet transform coefficients is taken into account, compression performance is enhanced and more image information is included of equivalent embedding capacity. In this way the watermarked image possesses not only good perceptual transparence but also better self-recovering capability compared with traditional techniques. For the SPIHT algorithm is an embedded coding algorithm, it can adjust the size of watermarking to change the embedding intensity according to the actual situation, which cannot be held by other methods. And Logistic map and cat map increase the security and ability of tamper localization of watermark. Finally, experimental results show the efficiency of the algorithm.