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.