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Method for embedding digital information in an image

  • US 5,859,920 A
  • Filed: 11/30/1995
  • Issued: 01/12/1999
  • Est. Priority Date: 11/30/1995
  • Status: Expired due to Term
First Claim
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1. A method of embedding digital data in a source image, comprising the steps of:

  • a) generating a multi-level data image representing the digital data;

    b) convolving the multi-level data image with a variable frequency encoding carrier image to produce a frequency dispersed data image;

    wherein the variable frequency encoding carrier image is generated by the steps of;

    b1) providing a 1-dimensional variable frequency carrier signal, wherein the 1-dimensional variable frequency carrier signal is a linear chip signal defined by;

    ##EQU3## where r is the distance in units of pixels, fmin is the minimum frequency of the chirp, fmax is the maximum frequency of the chirp, and L is the total length of the chirp in the units of pixels; and

    b2) converting the 1-dimensional variable frequency carrier signal to a 2-dimensional variable frequency carrier signal using a rotational sweep; and

    c) adding the frequency dispersed data image to the source image to produce a source image containing embedded data.

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