Patent ID: 7280669
Filing Date: 2007-10-09
Classification: G06T,H04N

Abstract:
1. A method for embedding watermark into a digital image having a luminance component, comprising: (a) transforming said luminance component into coefficients of a frequency domain having a first frequency area and a second frequency area; (b) generating a replacement coefficient from a coefficient of said first frequency area and said watermark; (c) replacing a coefficient of said second frequency area with said replacement coefficient, whereby said watermark is embedded into said digital image; (d) transforming said digital image embedded with said watermark into an inverse frequency domain; (e) transforming the luminance component of the digital image embedded with said watermark into the coefficients of the frequency domain; (f) generating a watermark for authentication; (g) extracting said watermark embedded in said digital image by using the coefficients of said first and second frequency domains; and (h) authenticating said digital image by finding a correlation of said extracted watermark and said watermark for authentication, wherein (h) comprises: (h1) finding the maximum peak value and the position of said maximum peak value from the correlation between said extracted watermark and said watermark for authentication; (h2) finding the 4th moment from said correlation; (h3) judging that said extracted watermark is same with said watermark for authentication in case where said 4th moment is over a predetermined critical value, the maximum peak value of said correlation is over a predetermined critical value, and the position of the maximum peak value of the extracted watermark and the watermark for authentication are the same.