This application relates to the field of digital watermark technologies and discloses a digital watermark embedding method and extraction method, a digital watermark embedding apparatus and extraction apparatus, and a digital watermark system. The method includes obtaining a digital watermark of a composite file, splitting the digital watermark into N sub-watermarks according to a carrier quantity N of the composite file, each sub-watermark being corresponding to partial content of the digital watermark, embedding an i.sup.th sub-watermark in an i.sup.th carrier of the composite file, to obtain an i.sup.th target carrier, and integrating N target carriers into a target file. This application resolves a problem in the related technology that a digital watermark technology cannot ensure integrity of an order file, and protects carriers of a composite file, thereby ensuring security and integrity of the composite file.

A method for watermarking documents comprising: identifying and locating spaces in a received original document (10) by a location analysis (110) module which distinguishes between intra-word spaces and inter-word spaces; minimizing an error probability of interference between intra-word spaces and inter-word spaces in the watermarked document (20) by an optimization module (111); encoding (113) the message (30) into codewords and encoding (114) the codewords into the watermark;
embedding the watermark to generate (115) the watermarked document (20) by modifying the intra-word spaces and inter-word spaces of the original document (10).

Optical code signal components are generated and then transformed into signal bearing art that conveys machine readable data. The components of an optical code are optimized to achieve improved signal robustness, reliability, capacity and/or visual quality. An optimization program can determine spatial density, dot distance, dot size and signal component priority to optimize robustness. An optical code generator transforms tiles of an optical code or image embedded with the optical code into signal-bearing art using stipple, Voronoi, Delaunay or other graphic drawing methods so as to retain prioritized components of the optical code. The optical code is merged into a host image, such as imagery, text and graphics of a package or label, or it may be printed by itself, e.g., on an otherwise blank label or carton. A great number of other features and arrangements are also detailed.

A method and an apparatus for generating cover images for steganography are provided. The steganographic framework is designed based on an image generation system. The apparatus may encode a message to obtain a binary sequence. The apparatus may obtain a plurality of binary segments of a particular length based on the binary sequence. For each binary segment of the plurality of binary segments, the apparatus may select an image of a semantic content (e.g., a numeral digit) from a dictionary of images of random semantic contents (e.g., random numeral digits) based on the binary segment. The apparatus may combine the selected images to form at least a portion of a cover image denoting a combination of the semantic contents of the selected images (e.g., a plurality of numeral digits).

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for applying a ghost image to an identification document that include the actions of obtaining a first image of an object. Identifying a first portion of the first image that corresponds with the object and a second portion of the first image that does not correspond with the object. Generating a second image by converting the first image to a negative image, and removing the second portion of the first image that does not correspond to the object. Generating a halftone image from the second image. Causing optically variable media to be applied to the identification document based on the halftone image. The optically variable media has a first appearance when viewed from in reflected light at a first angle and a second, different appearance when viewed in reflected light at a second, different angle.

A method for authenticating digital information includes obtaining, in digital form, information for authentication; preparing the information for processing; such preparation including converting the information into a digital image; identifying segments of content in the digital image; grouping the segments of content into one or more segment groups; generating a marking sequence comprising shifting at least one of the one or more segment groups in one or more directions; and applying the marking sequence to the digital image, creating a unique marked copy of the digital image.

Disclosed are methods, systems, devices, apparatus, media, and other implementations, including a method that includes obtaining input visual data comprising a sequence of symbols, selected from a symbol set, with each of the symbols associated with a glyph representation. The method also includes obtaining a code message comprising code message symbols, and modifying at least one of the symbols of the input visual data to a different glyph representation associated with a respective at least one of the code message symbols to generate, at a first time instance, a resultant coded visual data.

Optical code signal components are generated and then transformed into signal bearing art that conveys machine readable data. The components of an optical code are optimized to achieve improved signal robustness, reliability, capacity and/or visual quality. An optimization program can determine spatial density, dot distance, dot size and signal component priority to optimize robustness. An optical code generator transforms tiles of an optical code or image embedded with the optical code into signal-bearing art using stipple, Voronoi, Delaunay or other graphic drawing methods so as to retain prioritized components of the optical code. The optical code is merged into a host image, such as imagery, text and graphics of a package or label, or it may be printed by itself, e.g., on an otherwise blank label or carton. A great number of other features and arrangements are also detailed.

Generation of one dimensional guilloche patterns able to be affixed on a document, each guilloche pattern being able to encode variable alphanumeric data providing a different appearance to each guilloche pattern, by formatting alphanumeric data to be encoded in the form of a predefined number of data blocks with a predefined size, generating a carrier function having a plurality of parameters, the formatted data blocks forming at least one of the parameters, and modulating the carrier function by the formatted data blocks so as to encode the alphanumeric data graphically, each data block defining a guilloche pattern, the number of data blocks defining the number of guilloche patterns, the carrier function associated with a formatted data block is modulated locally, each datum of the block being encoded locally in the guilloche pattern, by interpolation of a predefined point associated with the carrier function.

One aspect of the present invention discloses a watermark insertion method. The method includes: segmenting target text into pieces of page content; obtaining a watermark variable comprising a line alternation value indicative of a watermark mode changed for each line of the segmented page content and a watermark mode setting value; and applying a flip-flop component insertion algorithm for inserting a watermark into each of the pieces of segmented page content based on the obtained watermark variable.