应用提升格式小波变换的数字水印算法

Watermark algorithm using lifting-scheme wavelet transform

针对彩色文物图像在WEB共享时面临的版权保护问题,提出了一种改进的应用提升格式小波变换的数字水印算法。采用YCbCr颜色模型以保证视觉系统对亮度和色彩的敏感性;使用Daubechies9/7双正交小波对图像信号进行频域转换后嵌入水印,提高水印的抗攻击能力,同时采用提升格式实现小波变换,提高算法的稳定性;将水印图像的低频和中频信息嵌入到文物图像的中频信息中,并利用频域相邻系数关系动态地改变嵌入位置和数值来实现嵌入过程,提高水印嵌入的健壮性和安全性。实验结果表明,本算法在嵌入水印后,文物图像视觉质量损失较小,其峰值信噪比(PSNR)为51.6024,高于同类算法;在抗几何攻击和有损压缩攻击等方面,效果比LSB算法和DCT算法有较大程度的提高。此技术可应用于数字博物馆等具有高精度安全要求的领域中。

An improved algorithm based on a lifting scheme wavelet transform is proposed to protect the copyright of a cultural relic image during Web sharing. The YCbCr color space is used to ensure the lightness and color sensitivity in a visual system. Then,the Daubechies9/7 biorthogonal wavelet is introduced to transform the image into a frequency domain and to hide watermark information to improve the anti-attacked capability. Meanwhile,a lifting scheme is used to enhance the stability of the algorithm. Finally, in order to increase algorithm＇s robustness and security, a new embedding method is presented to embed the intermediate and high frequency watermark information into image＇s high frequency coefficients, and the embedded position is switched dynamically in depending on the neighborhood coefficients. Experimental results indicate that the cultural relic image show a better visual quality after embedding watermark,and the Peak Signal Noise Ratio（PSNR） of the watermarked ira-age is 51. 602 4, which is better than that of other algorithms. Compared with LSB and DCT algo- rithms, the proposed algorithm has good performance in the anti-attack and lossy compression and is suitable for the fields which request high security such as digital museums.