METHOD OF WATERMARKING FOR BINARY IMAGES

A technology of digital watermarking for binary images (including documents) is provided, which is capable of adjusting the amount of information to be embedded while avoiding the deterioration of image quality as far as possible. The watermark information is inserted by giving the standard for judgment of modification and the order of preference for modification according to the characteristic properties of the human visual sense for binary images and performing modification on pixels sequentially in the descending order of preference.