Personal authentication medium issuing method

A personal authentication medium issuing apparatus which issues personal authentication media, comprising:

• an image input device which inputs main image information,
• a determining section which determines whether a gradation correction process is required for the main image information input from the image input device,
• a preprocessing section which performs a preprocessing operation containing the gradation correction process for the main image information which is determined to require a gradation correction process by the determining section and performs a preprocessing operation containing no gradation correction process for the main image information which is determined not to require a gradation correction process by the determining section,
• an electronic watermark embedding section which forms synthesized image information by embedding sub-information set in an invisible state to naked eyes of a human being with respect to main image information preprocessed by the preprocessing section, and
• a forming section which forms a personal authentication medium by printing synthesized image information formed by the electronic watermark embedding section on a recording medium.

A personal authentication medium issuing method which issues personal authentication media, comprising:

• inputting main image information,
• determining whether a personal authentication medium formed by use of the main image information is required to be checked based on the input main image information,
• forming synthesized image information by embedding sub-information set in an invisible state to naked eyes of a human being with respect to the input main image information,
• forming a personal authentication medium by printing the thus formed synthesized image information on a recording medium, and
• selectively sorting the thus formed personal authentication media into personal authentication media determined to be completely formed and personal authentication media determined to require a checking process.

A personal authentication medium issuing method which issues personal authentication media, comprising:

• inputting main image information,
• determining whether a gradation correction process is required for the input main image information,
• performing a preprocessing operation containing the gradation correction process for the main image information which is determined to require a gradation correction process by the above determining step and performing a preprocessing operation containing no gradation correction process for the main image information which is determined not to require a gradation correction process by the above determining step,
• forming synthesized image information by embedding sub-information set in an invisible state to naked eyes of a human being with respect to the main image information subjected to the preprocessing operation, and
• forming a personal authentication medium by printing the thus formed synthesized image information on a recording medium.

A truth determination apparatus for a printed matter which determines the truth of the printed matter, comprising:

• an image reading device which reads an image of a printing surface of a printed matter,
• a first analyzing section which detects a carrier pattern formed of print pixels in which color components set in a complementary relation make pair from an image of an area in which sub-information is embedded in the image of the printing surface read by the image reading device,
• a second analyzing section which detects a block formed of a plurality of print pixels having concentration values which lie outside a preset range from the image of the area in which sub-information is embedded in the image of the printing surface read by the image reading device, and
• a truth determining section which determines that a printed matter in which a carrier pattern is detected by the first analyzing section and the number of blocks detected by the second analyzing section and having concentration values which lie outside a preset range is smaller than a preset number is true.

A truth determination method for a printed matter which determines the truth of the printed matter, comprising:

• reading an image of a printing surface of a printed matter,
• detecting a carrier pattern formed of print pixels in which color components set in a complementary relation make pair from an image of an area in which sub-information is embedded in the read image of the printing surface,
• detecting a block formed of a plurality of print pixels having concentration values which lie outside a preset range from the image of the area in which sub-information is embedded in the read image of the printing surface, and
• determining that a printed matter in which the carrier pattern is detected and the number of detected blocks having concentration values which lie outside a preset range is smaller than a preset number is true.