一种基于DWT-DCT变换域的全息水印技术

A holographic digital watermarking technology based on DWTDCT transform domain

在研究傅里叶全息技术基础上,提出了一种结合离散小波变换和离散波变换(DWT-DCT)变换的彩色图像数字水印算法,使得水印拥有强鲁棒性和不可见性。首先,对水印信息进行傅里叶变换,并生成全息水印图;其次,将载体图像在RGB空间内的蓝色B分量进行小波分解,对其低频部分进行DCT;最后,将水印全息图嵌入其高频系数中。实验结果发现,以k=0.05的强度嵌入水印后,含水印图像的峰值信噪比(PSNR)达到47,能有效抵抗信号处理和裁切攻击,同时提取出的水印和原始水印的相似性(NC值)能保持在0.75以上,说明本文水印算法有较强的鲁棒性和不可见性。本文算法能够抵抗裁切、滤波、噪声和JPEG压缩攻击,可用于数字图像版权保护方面。

Based on the research of the Fourier holographic technology, a digital watermarking algorithm of color image combined with discrete wavelet transform and discrete cosine transform （DWT-DCT） transforms is proposed to make the robustness and invisibility of the watermark image better. Firstly, the watermark image is transformed by Fourier transforms and generated into the hologram image. Second- ly,the B component of the vector image in the RGB color space is decomposed by wavelet transform,and its low frequencies ae transformed by DCT. Finally, the hologram message was embed into the high frequency domain. The experimental results show that after the watermark image is embedded with strength of k=0. 05, the peak signal to noise ratio （PSNR） reaches 47 in the embedded image,and the watermark can resist those attacks of signal processing and cropping. At the same time,the similarity （NC value ） of the extracted watermark and the original watermark can be maintained at more than 0.75, which indicates that the watermark has strong robustness and invisibility. This algorithm can resist cutting, filtering,noise and JPEG compression, and it can be used for copyright protection of digital images.