Importance

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Abstract

An acquired (e.g., scanned) image contains an imperceptible periodic signal component (e.g., a sinusoid), decoding of which can be used to automatically determine a linear geometric relationship between the acquired image and the original image in which the signal was embedded, without having the original image available during the decoding process. This known geometric relationship allows for linear geometric properties of the acquired image, such as alignment and scaling, to be automatically matched with those of the original image so that the acquired image may be automatically oriented and scaled to the size of the original image. The embedded periodic signals produce a distinct pattern of local peak power concentrations in a spatial frequency amplitude spectrum of the acquired image. Using geometric constraint information about the embedded signals when the signals were originally embedded in the image, the locations and spatial frequencies of the signals are decoded from the image, providing a linear mapping between the peak power concentrations of the acquired and original image spatial frequency amplitude spectra. This linear mapping can be used to compute the linear geometric relationship between the two images. In an illustrated embodiment, the acquired image contains a set of sinusoidal signals that act as a grid. Decoding of the sinusoids does not require the original image, only information about the predetermined geometric relationship of the embedded sinusoids.

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First Claim