US 6,700,990 · Granted 2004-03-02

Digital watermark decoding method

To decode a digital watermark from an image notwithstanding geometrical corruption of the image (e.g., scale, rotation, etc.), a Fourier-Mellin transform is advantageously used. In a particular method, an image is transformed to the spatial frequency domain. Transformed components of the image are then pattern-matched to reference frequencies, and the thus-altered image components are transformed back to the spatial image domain to effect registration of the image prior to watermark decoding.

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