一种感兴趣区域防溢出数字水印算法

目的针对工程设计图纸、医学影像等存在大量边缘值像素点的图像在嵌入水印时容易出现像素值溢出的问题,文中提出一种基于感兴趣区域防溢出的水印方案。方法该方案使用改进后的区域生长法分割原始图像得到不规则形状的ROI,再通过填充像素值得到矩形水印嵌入区域,对该区域进行提升小波变换,并经过Arnold置乱,通过对水印嵌入区域的分块和扫描,跳过边缘像素值,使用奇偶映射的方法将制成QR码的水印信息嵌入至宿主图像。结果嵌入水印后图像边缘仍完整,像素值溢出现象得到大大改善,嵌入水印后图像峰值信噪比高于48db,水印不可见性高于一般水印嵌入方案,满足高精度图像对水印不可见度要求,且经过攻击后仍能实现水印的提取。结论该方案充分考虑到含有大面积背景和大量边缘像素值图像的特点,保证认证水印嵌入至图像关键ROI区域,在保证原图质量的基础上实现了防溢出的水印嵌入,经过攻击后提取的水印仍能够读取认证信息,在包装印刷工程中具有实际应用价值。

An Anti-overflow Digital Watermark Algorithm in Region of Interest

The work aims to propose an anti-overflow watermark scheme based on region of interest (ROI), regarding the problem of pixel overflow in watermark embedding in images with a mass of bordered pixels like drawing of engineering design and medical images. The scheme used the improved region growing algorithm to segment irregularly shaped ROI from the original image, then filled the region with pixels to get rectangular region of watermark embedding (ROW). After applying lifting wavelet transform and Arnold transformation to ROW, the scheme partitioned and scanned the region to embed the watermark which was in QR code into the host image with the means of parity mapping, while bordered pixels were skipped. The edge of images with embedded watermark still remained integrated and the appearance of pixel overflow was greatly reduced. The PSNR of watermark embedded images were greater than 48 db, which indicated that the invisibility of watermark was greater than general watermark embedding schemes and satisfied the requirement of watermark invisibility of high-precision images; moreover, after the attacks, the extraction of watermark could still be achieved. The proposed scheme takes full account of the feature of images with large area background and mass bordered pixels, and makes sure that the certified watermark is embedded into critical ROI of the image. The scheme realizes the anti-overflow watermark embedding process on the basis of quality guarantee of the original image. The extracted watermark from images under attack can still show authentication information. The proposed scheme has practical application value in packaging and printing and engineering.