Watermark information extraction apparatus and method of controlling thereof

A watermark information extraction apparatus comprising:

• input means for inputting a document in which watermark information has been embedded by a digital watermark;
• character recognition means for acquiring character information that includes character code information and font information of a prescribed character contained in the document image, as well as information indicative of position of the prescribed character in the document image;
• document image reconstruction means for reconstructing a document image, which prevailed before the embedding of watermark information, based upon the character information acquired and prescribed character size information;
• and
• watermark information extraction means for extracting the watermark information based upon result of comparison between size of the prescribed character in the reconstructed document image and the size of a prescribed character in the document image in which watermark information has been embedded.

A watermark information extraction apparatus comprising:

• input means for inputting a document in which watermark information has been embedded by a digital watermark;
• character recognition means for acquiring character information that includes character code information and font information of a prescribed character contained in the document image, as well as information indicative of position of the prescribed character in the document image;
• document image reconstruction means for reconstructing a document image, which prevailed before the embedding of watermark information, based upon the character information acquired;
• and
• watermark information extraction means for extracting the watermark information based upon angle of inclination of the prescribed character in the reconstructed document image and angle of inclination of a prescribed character in the document image in which watermark information has been embedded.

A method of controlling a watermark information extraction apparatus for extracting watermark information from a document image in which the watermark information has been embedded by a digital watermark, said method comprising:

• a character recognition step of acquiring character information that includes character code information and font information of a prescribed character contained in the document image, as well as information indicative of position of the prescribed character in the document image;
• a document image reconstruction step of reconstructing a document image, which prevailed before the embedding of watermark information, based upon the character information acquired and prescribed character size information;
• and
• a watermark information extraction step of extracting the watermark information based upon result of comparison between size of the prescribed character in the reconstructed document image and the size of a prescribed character in the document image in which watermark information has been embedded.

A method of controlling a watermark information extraction apparatus for extracting watermark information from a document image in which the watermark information has been embedded by a digital watermark, said method comprising:

• a character recognition step of acquiring character information that includes character code information and font information of a prescribed character contained in the document image, as well as information indicative of position of the prescribed character in the document image;
• a document image reconstruction step of reconstructing a document image, which prevailed before the embedding of watermark information, based upon the character information acquired;
• and
• a watermark information extraction step of extracting the watermark information based upon angle of inclination of the prescribed character in the reconstructed document image and angle of inclination of a prescribed character in the document image in which watermark information has been embedded.