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Method for embedding and extracting digital watermark on lowest wavelet subband

  • US 7,343,025 B2
  • Filed: 12/15/2003
  • Issued: 03/11/2008
  • Est. Priority Date: 10/02/2003
  • Status: Expired due to Fees
First Claim
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1. A method of embedding a digital watermark on a wavelet lowest subband of an original image, the method comprising the steps of:

  • wavelet transforming the original image into n levels;

    setting the wavelet lowest subband of the wavelet-transformed original image as a watermark embedment region;

    high-frequency filtering an original picture LLn of the watermark embedment region to generate a mirror picture LLn

    from which a high frequency component of the original picture LLn has been eliminated;

    generating (i) index information designating a plurality of pixel positions within the watermark embedment region where the watermark is to be embedded, and (ii) a sequence of watermark values to be embedded in said pixel positions, respectively;

    calculating an embedment strength λ

    for each said pixel position of the watermark embedment region, considering a variance degree of an original picture LLn coefficient value;

    for each said pixel position, selectively altering the original picture LLn coefficient value based on (a) a corresponding mirror picture LLn

    coefficient value, (b) the watermark value to be embedded in said pixel position, and (c) the embedment strength λ

    of said pixel position; and

    selectively embedding the watermark at each said pixel position with the selectively altered original picture LLn coefficient value while skipping watermark embedment where the original picture LLn coefficient value before and after said altering differs by more than a predetermined value associated with the corresponding embedment strength λ

    .

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