为了更好地进行图像数字水印的识别,基于对数极坐标仿射(LPM),设计和应用了5种滤波器,即经典匹配滤波器、振幅滤波器、相位滤波器、双态相位滤波器和改进的滤波器。为比较各种滤波器对数字水印的识别能力,将这些滤波器对嵌入图像中的数字水印进行了两种情况的检测实验。实验结果表明,当含数字水印的图像没有几何失真,即没有旋转、缩小和放大、平移等变化时,改进的滤波器、相位滤波器和双态相位滤波器均能对图像中的数字水印进行识别,改进的滤波器在图像数字水印检测中的识别能力要强于相位滤波器和双态相位滤波器;当含数字水印的图像发生微小几何变化,即旋转10°和尺寸缩小为原图像的0 9时,则传统的4种滤波器都不能对图像中的数字水印进行识别,但改进的滤波器仍具有对图像中数字水印进行识别的能力。

Based on log polar mapping, five filters have been designed and applied in this paper. In order to check the digital watermark embedded in digital images, we compared the classical matched filter, amplitude only filter, phase only filter, binary phase only filter and a new filtering method. Experimental results demonstrate that the new filter, phase only filter and binary phase only filter can be used to identify the digital watermark in the digital images when there is no rotation, scaling and translation for the images embedded digital watermark; Suppose the image embedded digital watermark is rotated ten degree and scaled down ten percent, it can be found the classical matched filter, amplitude only filter, phase only filter and binary phase only filter can't be used to identify the digital watermark in the digital images ,but this new filtering method can still be used to identify the digital watermark in digital images.