Method for embedding and extracting digital watermark on lowest wavelet subband
First Claim
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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Abstract
A for embedding a digital watermark on a wavelet lowest subband includes: setting a DC component region of a multi-stage wavelet-transformed original copy image to a watermark embedment region, and high-frequency filtering an original picture LLn of the embedment region; generating index information for designating a pixel position, and a watermark sequence to be embedded; calculating an embedment strength λ for each position of the watermark embedment region; in case the watermark sequence is sequentially embedded on an embedded position designated by the index information, mutually comparing the original picture LLn coefficient value for each embedded position with a mirror picture LLn′ coefficient value, and then altering the original picture LLn coefficient value; and in case the original picture LLn coefficient value is differentiated above a predetermined value with reference to the coffesponding embedment strength λ, skipping the watermark embedment for the position.
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Citations
9 Claims
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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:
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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; andselectively 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
. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification