An image forming apparatus includes an embedding device and an image output device. The embedding device is configured to embed a pair of identical electronic information in a pair of electronic embedment areas outside a print guarantee area and within a printable area of a recording medium. The pair of electronic embedment areas is along a pair of opposite sides of the recording medium. The image output device is configured to print out an image with the pair of identical electronic information embedded on the recording medium.

Some implementations may include a computer-implemented method for applying at least two digital watermarks to a digital document, the method including: receiving a digital document comprising visual contents; generating a first digital watermark to be visually presented at a first time point; generating a second digital watermark to be visually presented at a second time point, the second digital watermark being different from the first digital watermark and the second time point being different from the first time point; and applying both the first digital watermark and second digital watermark to the digital document t.

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for determining, by a pixelation device, an arrangement of pixels for generating representations of data for a document; adjusting, by an increment module and based on the arrangement of pixels, an optical density of one or more pixels included in the arrangement; associating, by the pixelation device, a plurality of distinct types of credential data with one or more line patterns included in the arrangement of pixels; and generating, by the pixelation device, multiple line patterns at a document, the multiple line patterns encoding the plurality of distinct types of credential data.

Identifiers or references to supplemental information or content regarding images may be steganographically encoded into the images. The identifiers or references may be encoded into least significant bits or less significant bits of pixels within the image that may be selected on any basis. The identifiers or references may include alphanumeric characters, bar codes, symbols or other features. When an image is captured of an image having one or more identifiers or references steganographically encoded therein, the identifiers or references may be interpreted, and the supplemental information or content may be accessed and displayed on a computer display. In some embodiments, the supplemental information or content may identify and relate to a commercial product expressed in an image, and may include a link to one or more pages or functions for purchasing the commercial product.

Some implementations may include a computer-implemented method for applying at least two digital watermarks to a digital document, the method including: receiving a digital document comprising visual contents; generating a first digital watermark to be visually presented at a first time point; generating a second digital watermark to be visually presented at a second time point, the second digital watermark being different from the first digital watermark and the second time point being different from the first time point; and applying both the first digital watermark and second digital watermark to the digital document t.

Some implementations may provide a computer-implemented method for validating a digital document, the method including: receiving, at a computing device, the digital document comprising at least two digital watermarks, the digital document issued by a central entity; retrieving a first digital watermark from the digital document, the first digital watermark visually presented at a first time point; retrieving a second digital watermark from the digital document, the second digital watermark visually presented at a second time point, the second digital watermark being different from the first digital watermark and the second time point being different from the first time point; and reading the digital document based on the retrieved first and second digital watermarks.

Example implementations relate to multiple payload pantograph. Some examples may include a first pattern generation engine to generate a first pattern. The first pattern may be a data-bearing pattern encoding a first payload. Additionally, some examples may include a second pattern generation engine to generate a second pattern, the second pattern (by itself or in combination with the first pattern) may represent a second payload. The second payload may be camouflaged by a combination of the first pattern and the second pattern. Some examples may also include a pantograph generation engine to generate a multiple payload pantograph including the first pattern and the second pattern. The multiple payload pantograph may include the first pattern in one of the pantograph background or the pantograph foreground.

An information embedding device, comprising: a memory; and a processor configured to execute a procedure, the procedure including: from an image, detecting, as an embedding target pixel block, a pixel block having a pixel value that, after being changed by a specific value corresponding to information to be embedded into the image, will be within a first specific range of an average value of pixel values of a surrounding pixel block; and changing the pixel value of the detected embedding target pixel block by the specific value.

Related are a method and system for embedding information into encoding information. The method comprises the steps of first embedding the information into an embeddable image or a virtual image using a frequency domain embedding method, and then overlaying the embeddable image or the virtual image into a printed file in need of a variable code or a fixed code using a spatial domain processing method. In this way, the information not perceived by human eyes may be embedded into the encoding information using frequency domain and spatial domain transformation, the counterfeiting difficultly is extremely large, the cost is high, and the anti-counterfeiting purpose is achieved; and furthermore, the printing cost is not increased, thereby being beneficial to wide promotion and application.

Examples disclosed herein relate to providing access to digital content using a machine-readable link. As an example, an annotation comprising digital content, for a portion of a digital content, is identified in response to a print request. Based on the annotations, a machine-readable link associated with the digital content is generated. Subsequently, a printable format version of the digital document comprising the machine-readable link, and excluding the annotation is obtained wherein the machine-readable link is readable by a computing device to obtain access to the digital content over a communication network.