METHOD OF EXTRACTING DIGITAL WATERMARK INFORMATION AND METHOD OF JUDGING BIT VALUE OF DIGITAL WATERMARK INFORMATION

According to a digital watermark information extracting method, pixel data located at predetermined positions on X-Y coordinate used when digital watermark information is embedded are extracted from image data, and the data value of the pixel data is compared with a reference value to judge whether the watermark information is embedded in the pixel data concerned. This processing is repetitively executed while a geometrical deformation is applied to the image data until it is confirmed that the information is embedded in the pixel data.