混沌映射的半脆弱图像数字水印算法

提出了一种抗JPEG有损压缩的半脆弱图像数字水印算法．该算法充分利用混沌映射对初值的敏感性，并根据JPEG图像压缩过程中DCT系数的不变特性，将预先量化的DCT低频系数和水印密钥合成为混沌系统的初值，经过多次混沌迭代生成水印信号．根据水印信号调整块对间DCT系数的大小，完成水印的嵌入调制．实验结果表明，该算法对JPEG有损压缩具有良好的鲁棒性．同时可对图像内容的恶意篡改进行精确的检测与定位．

Chaos Based Semi-Fragile Image Watermarking Algorithm

A semi-fragile image watermarking technique that accepts JPEG lossy compression was de- veloped.With the high sensitivity on initial value of chaotic mapping and the invariant properties of DCT coefficients before and after JPEG compression,the pre-quantized low DCT coefficients and a wa- termarking key are combined as the initial value of logistic map for generating the watermark.The wa- termarked image was obtained by modifying the DCT coefficients in block pairs according to the water- mark.The experimental results showed the effectiveness of this system.The proposed technique was robust against JPEG lossy compression,but sensitive to the malicious attacks on the watermarked im- age.In the meantime,it can localize the tampers correctly and accurately.