Patent ID: 7065226

Claim:
A method of embedding digital watermark information b 1 –b n (2≦n) in image data, comprising the steps of: dividing the image data into a plurality of areas S each consisting of M×N (1≦M, N) pixels; defining an area G consisting of P×Q (1≦P, Q) of the areas S; allocating each of the areas S constituting said area G to some one of: areas T 1 –T n whose pixel values are changed, areas J 1 –J k (1≦k) in which information p 1 –p k (1≦k) specifying an embedding format for embedding said digital watermark information b 1 –b n in said areas T 1 –T n , and areas H 1 –H m (1≦m) whose pixel values are not changed; corresponding each of said T 1 –T n , whose pixel values are changed, to each of said digital watermark information b 1 –b n and changing the pixel value of each area T according to a bit value; locating areas T 1 –T n , areas J 1 –J k and areas H 1 –H m in a predetermined same arrangement in said area G; and locating said area G repeatedly over entire image data, wherein: said digital watermark information b 1 –b n is embedded by increasing or decreasing pixel data values in the corresponding areas T 1 –T n according to a bit value (0, 1) of each bit of the digital watermark information b 1 –b n ; and said information p 1 –p k specifying said embedding format is embedded such that said information indicates a pattern of respective increasing/decreasing directions in the area T 1 –T n for a bit value of the digital watermark information, in each area G to which the area J 1 –J k embedded with said information p 1 –p k belong.