为了增强水印的不可见性和鲁棒性, 提出了一种基于图像特征区域的水印算法。首先利用SIFT(Scale Invariant Feature Transform)算法从载体图像蓝色B通道中提取图像特征点来进行优化和筛选, 根据优化后的稳定特征点及其特征尺度确定图像的特征区域, 再结合全息技术, 对原始水印图像进行双随机相位加密, 生成加密全息水印; 然后对特征区域进行离散余弦变换(DCT); 最后在其中频区域嵌入加密全息水印。在提取水印时无须借助原始图像, 是盲水印技术。实验结果表明: 该算法重建的水印图像与原始水印图像的NC值高达0.95; 水印的嵌入对图像质量影响很小, PSNR值高达55.97, 能够抵抗常规信号攻击及缩放、剪切、平移等几何攻击。

To enhance the invisibility and robustness of digital watermarking,a new strong resistance ability of the color image algorithm is proposed.The watermarked host image in RGB mode is separated,and blue B component is used as embedded watermark channel. By optimizing and screening the SIFT feature points from the B component, the local feature region of the optimized SIFT point and its characteristic scale are determined. Then the encrypted Fourier holography is used for original watermarking encryption and hologram generation,using the method of discrete cosine transform to embed the watermarking into the intermediate frequency area in the local feature region, the DCT transform is performed. By binding the watermarking and image features,the resynchronization between the embedding and extracting can be accomplished.The experimental results show that the NC between reconstructed watermark and original watermark is 0.95, meanwhile,the embedding watermark has little effect on image quality, the PSNR is 55.97, it can resist various common signals attack and has strong resistance ability of scaling, cropping, translating geometric attacks.