扩频鲁棒图像水印中的亮度越界处理方法

在扩频鲁棒图像水印中,在水印嵌入过程中的"频域-空域"变换会引起像素亮度值的越界,而现有的解决方案有可能导致水印检测值的大幅降低,并严重削弱了水印的鲁棒性.因此以典型的扩频水印机制为例,通过在空间域给出水印检测值的近似计算方法,研究了像素亮度越界现象对水印检测值的影响,发现对纹理较少的高亮度图像,像素的亮度越界将严重地降低水印检测值.最后提出了一种自适应的分块式亮度调整策略,分析和实验表明,新的调整策略能够有效地改进含水印图像的保真性和水印的鲁棒性.

On the Luminance Overflow in Spread Spectrum Robust Image Watermarking Schemes

In spread spectrum robust image watermarking schemes, images are watermarked in frequency domains and transformed back to spatial domains. Different from unlimited frequency coefficients, the volumes in spatial domains are usually limited, therefore luminance overflow frequently occurs on some pixels in watermarked images especially for those with high average luminance. In all existing solutions to this problem, noticeable decreases are generally introduced into the results of watermark detections, and the...