一种简化的基于分块模运算的安全数字水印算法

基于分块模运算的数字图像水印是一种有效的用于版权保护及盗版跟踪的空域图像水印算法。它通过在图像特征边缘点附近选择由3x3像素点所组成的块并调整该块平均亮度的值嵌入水印。然而，原算法需要存储原始图像的特征边缘点用于水印检测，而且还存在算法安全性问题。通过随机选择嵌入水印的像素块位置有效地简化了算法，并利用保持嵌入水印图像平均亮度不变改进了算法安全性。实验及理论分析证明了算法的有效性。

Simplified block-oriented and modular-arithmetic-based secure digital image watermarking algorithm

The digital image watermarking with block-oriented and modular-arithmetic-based is an effective spatial-domain watermarking algorithm for copyright protection and piracy tracing. It embeds watermark by selecting 3x3 neighboring pixels around the edges of the features and adjusting the mean intensities of the selected blocks. However, it is inconvenient for the original algorithm to extract watermark because the edge pixels of the original image are needed for watermark extraction. In addition, there exists security problem in the original algorithm. The algorithm is simplified by randomly selecting the blocks to embed watermark and the security is improved by maintaining the mean intensity of the watermarked image. The theoretic analysis and experimental results demonstrate the efficiency of the improved algorithm.