DIGITAL WATERMARK EMBEDDING APPARATUS FOR DOCUMENT, DIGITAL WATERMARK EXTRACTION APPARATUS FOR DOCUMENT, AND THEIR CONTROL METHOD

This invention provides a digital watermark embedding apparatus for a document, which can eliminate unnaturalness that may be experienced upon laying out characters in a document when watermark information is embedded, while maintaining the robustness of a document itself and the information size to be embedded of a digital watermark. A document image is input from an image input unit (11), and watermark information is input from a watermark information input unit (15). A region division unit (12) divides the document image into regions, and a circumscribing rectangle extraction unit (13) sets circumscribing rectangles for characters and extracts them as character images. A punctuation mark determination unit (14) determines a punctuation mark from the character image. A watermark information embedding unit (16) embeds watermark information by digital watermarking that shifts character images other than the character image determined to be a punctuation mark.