结合DCT与分形编码的自适应水印算法

An Adaptive Watermarking Algorithm Combined with DCT and Fractal Coding

提出并实现了一种结合DCT与分形编码的自适应水印算法。将宿主图像分成大小相同的不重叠方块,利用分形编码的拼贴误差对图像块进行分类,并构造原始宿主图像的二值特征标图,采用Arnold变换置乱二值特征标图和二值版权图标,再进行异或(XOR)运算得到隐秘水印。最后通过在子块DCT域中所选的三个中频系数的比较来完成隐秘水印的嵌入。实验表明,按该方法嵌入的水印具有良好的不可见性,也能较好抵抗高斯滤波、JPEG压缩、叠加噪声等处理。

An adaptive image watermarking algorithm combined with Discrete Cosine Transform （DCT） and fractal coding is proposed. The host image is split into non - overlapping fixed- size square blocks, which are categorized into two classes according to their collage errors obtained by performing baseline fractal ceding. The blocks classifica- tion is utilized to form a feature mark of the host image and determine imbedding strengths of the watermark in distinct blocks. Arnold transform is applied to scramble both the feature mark and binary copyright symbol. The watermark is the fusion of the scrambled feature mark and a scrambled binary copyright symbol （ using XOR operation）. Lastly, the watermErk is embedded into the middle frequency bands of DCT domains of distinct blocks by comparing the selected three coefficients. The experimental results show that the embedded watermark is invisible, and is also very robust against some image processing such as Gaussian filtering, JPEG compression and noising.