Information embedding device, information detecting device, information embedding and detecting system, information embedding method, information detecting method, information embedding program, information detecting program, information embedding and detecting program, and recording medium

An information detecting device that detects information embedded in a document image, comprising:

• a character region detecting unit that detects a character region from the document image;
• a character region dividing unit that divides the detected character region into a plurality of sub regions;
• a feature quantity extracting unit that extracts a feature quantity associated with each of the sub regions;
• an information value determining unit that determines the value of the embedded information by comparing the feature quantity associated with each of the sub regions with a value determined from a pseudorandom number sequence;
• and
• a feature quantity correcting unit that corrects the feature quantity obtained by the feature quantity extracting unit prior to the determination by the information value determining unit, wherein the feature quantity correcting unit comprises:
• a test image reading unit that reads a test image in which an arbitrary feature quantity is preset;
• a correction function identifying unit that identifies a correction function, based on the correspondence of the read value to the preset value in the test image;
• and
• a correction operating unit that performs correction using the correction function.

A method of embedding information in a document image having a character region using an information embedding device including a character region detecting unit, a character region dividing unit, a feature quantity increasing and decreasing unit, and a pseudorandom number adding unit, the information embedding device being controlled by a processor configured to carry out the method, the method comprising the steps of:

• detecting the character region from the document image using the character region detecting unit;
• dividing the character region into a plurality of sub regions using the character region dividing unit;
• and
• performing an operation using the feature quantity increasing and decreasing unit to increase or decrease a feature quantity with respect to each of the sub regions, to a value that is determined from a pseudorandom number sequence according to predetermined rules, wherein
• the predetermined rules to determine the value of the feature quantity involve the multiples of a suitable constant, and
• the method further comprises the step of using the pseudorandom number adding unit to add the value of a pseudorandom number to the value obtained by separating odd-number multiples from even-number multiples in accordance with the bit value of the information to be embedded.

A method of detecting information that is embedded in a document image using an information detecting device including a character region detecting unit, a character region dividing unit, a feature quantity extracting unit, an information value determining unit, and a feature quantity correcting unit, the information detecting device being controlled by a processor configured to carry out the method, the method comprising the steps of:

• detecting a character region from the document image using the character region detecting unit;
• dividing the character region into a plurality of sub regions using the character region dividing unit;
• extracting a feature quantity associated with each of the sub regions using the feature quantity extracting unit;
• determining the value of the embedded information using the information value determining unit by comparing the feature quantity associated with each of the sub regions with a value that is determined from a pseudorandom number sequence;
• and
• correcting the feature quantity obtained in the feature quantity extracting step using the feature quantity correcting unit, the feature quantity correcting step being carried out prior to the information value determining step, wherein the feature quantity correcting step comprises the steps of:
• reading a test image in which an arbitral feature quantity is preset;
• identifying a correction function based on the correspondence of the read value to the preset value in the test image;
• and
• performing correction using the correction function.