Apparatus and method for embedding watermark information in compressed image data, and apparatus and method for retrieving watermark information from compressed image data having watermark information embedded therein

摘要

A variable length decoding section extracts a codeword and an additional bit or bits corresponding to the codeword from compressed image data based on a code table. An embedding section embeds watermark information in a prescribed bit of the additional bits extracted by the variable length decoding section. A data connecting section connects the additional bits having the watermark information embedded therein by the embedding section with the codeword extracted by the variable length decoding section to produce a variable length code.