Patent ID: 6668068
Filing Date: 2003-12-23
Classification: G06T,H04N

Abstract:
An electronic watermark embedding device comprising:discrete cosine transform means for subjecting an input image to discrete cosine transform; electronic watermark detection means for detecting whether electronic watermark data to be inserted by an electronic watermark embedding means have been already inserted in the input image; electronically embedding means for inserting electronic watermark data into input image data converted by the discrete cosine transform means; and selection means for directly outputting the input image with no modification when it is detected by said electronic watermark detection means that the electronic watermark data has been inserted in the input image, or embedding new electronic watermark data into the input image when the insertion of the electronic watermark data is not detected, wherein said electronic watermark detection means performs the following operations: on the assumption that the original image and electronic watermark data candidates w(i)(i=1, 2, . . . ,n) are known, an image containing electronic watermark data is subjected to orthogonal transform to be converted into frequency components as f(1),f(2), . . . , F(n); representing the values of elements corresponding to the frequency components containing the electronic watermark data in the frequency domain by F(1), F(2), . . . , F(n), the electronic watermark data W(i) is calculated and extracted on the basis of f(i) and F(i) according to the following equation: W(i)=(F(i)âˆ’f(i))/f(i); the statistical similarity C between w(i) and W(i) is calculated and extracted by using vector inner product according to the following equation:C=WÂ·w/(WDÃ—wD), Here,W=(W(1), W(2), . . . , W(n)) w=(w(1), w(2), . . . , w(n)) WD=absolute value of vector W wD=absolute value of vector w â€œÂ·â€  represents inner product; when the statistical similarity C is above a predetermined value, it is detected that the electronic watermark data have been embedded in the image.