Over the past few years a number of research papers about reversible watermarks has been produced. Reversible watermarking is a novel category of watermarking schemes. It not only can strengthen the ownership of the original media but also can completely recover the original media from the watermarked media. This feature is suitable for some important media, such as medical and military images, because these kinds of media do not allow any losses. The aim of this paper is to define the purpose of reversible watermarking, reflecting recent progress, and provide some research issues for the future.

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Reversible Watermarking: Current Status and Key Issues

A portable data terminal that includes a housing and an environmentally responsive device for collecting data about the environment surrounding the housing. The portable data terminal also includes an encoded information reader unit with one or more data collection hardware devices, which can capture data encoded in decodable indicia, e.g., bar codes. In one embodiment, the portable data terminal is configured to operate in a mode that processes the decodable indicia, and the environmental data so as to correlate the information decoded in the decodable indicia with the environmental data.

Portable data terminal

This paper proposes a lossless data hiding technique for JPEG images based on histogram pairs It embeds data into the JPEG quantized 8x8 block DCT coefficients and can achieve good performance in terms of PSNR versus payload through manipulating histogram pairs with optimum threshold and optimum region of the JPEG DCT coefficients It can obtain higher payload than the prior arts In addition, the increase of JPEG file size after data embedding remains unnoticeable These have been verified by our extensive experiments

Reversible data hiding for JPEG images based on histogram pairs

Lossless data hiding in JPEG bitstream

We propose an algorithm to embed data directly in the bitstream of JPEG imagery. The motivation for this approach is that images are seldom available in uncompressed form. Algorithms that operate in spatial domain, or even in coefficient domain, require full (or at best) partial decompression. Our approach exploits the fact that only a fraction of JPEG code space is actually used by available encoders. Data embedding is performed by mapping a used variable length code (VLC) to an unused VLC. However, standard viewers unaware of the change will not properly display the image. We address this problem by a novel error concealment technique. Concealment works by remapping run/size values of marked VLCs so that standard viewers do not lose synchronization and displays the image with minimum loss of quality. It is possible for the embedded image to be visually identical to the original even though the two files are bitwise different. The algorithm is fast and transparent and embedding is reversible and file-size preserving. Under certain circumstances, file size may actually decrease despite carrying a payload.

Data Embedding in JPEG Bitstream by Code Mapping

A method is described in which metadata regarding a document is encoded as 2d barcode printed on the same recording medium as the document, where the metadata includes an access history of the document and other information. When a printed document including such barcode is copied, the copy includes new barcode containing updated metadata that replaces the original barcode, where the updated metadata includes a record of the current copying or scanning action. When a printed document including such barcode is scanned, the metadata contained in the barcode is extracted and stored. Also described is a document management system including a server connected to one or more clients, scanners, printers, and a storage device for storing documents and metadata. The server includes a digital stamp engine that generates barcode data representing metadata, and supports a variety of workflows including print, barcode generation, scan, copy, barcode update, etc.

Document management method using barcode to store access history information

In lossless watermarking, it is possible to completely remove the embedding distortion from the watermarked image
and recover an exact copy of the original unwatermarked image. Lossless watermarks found applications in fragile
authentication, integrity protection, and metadata embedding. It is especially important for medical and military
images. Frequently, lossless embedding disproportionably increases the file size for image formats that contain lossless
compression (RLE BMP, GIF, JPEG, PNG, etc...). This partially negates the advantage of embedding information as
opposed to appending it. In this paper, we introduce lossless watermarking techniques that preserve the file size. The
formats addressed are RLE encoded bitmaps and sequentially encoded JPEG images. The lossless embedding for the
RLE BMP format is designed in such a manner to guarantee that the message extraction and original image
reconstruction is insensitive to different RLE encoders, image palette reshuffling, as well as to removing or adding
duplicate palette colors. The performance of both methods is demonstrated on test images by showing the capacity,
distortion, and embedding rate. The proposed methods are the first examples of lossless embedding methods that
preserve the file size for image formats that use lossless compression.

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Lossless data embedding with file size preservation

A method of authenticating a document, typically a printed document, is disclosed. The method comprises: (a) processing a first area of a source document according to a first authentication level to generate first authentication data; (b) processing a second area of the source document according to a second authentication level to generate second authentication data, the second authentication level being different from the first authentication level; (c) generating barcode data representing at least the first and second authentication data; and (d) carrying out at least one of: (d1) embedding the barcode data to the source document to generate a processed document; and (d2) printing the barcode data on a recording medium.

Method and apparatus for authenticating printed documents

Disclosed is a method for determining optimum color gradation levels used by a color gradation barcode in a system including a rendering device for rendering the barcode and a detector for detecting the barcode. The method includes: (a) obtaining input color gradation data; (b) rendering, by using the rendering device, a test pattern based on the input color gradation data, the test pattern comprising at least one color gradation pattern; (c) detecting, by using the detector, the rendered test pattern to generate detected color gradation data; (d) based on the detected color gradation data and the input color gradation data, determining a plurality of optimum color gradation levels to be used for a color gradation barcode; and (e) storing the plurality of optimum color gradation levels.

Color barcode with enhanced capacity and readability for a closed loop system

Disclosed is a method for determining optimum noise filter setting to be used by a scanner in a system including a printer and a detector forming a closed loop system. A test image including a plurality of horizontal lines, vertical lines, slanted lines and dots are printed using the printer and scanned back using the scanner. The scanned test image data is compared to the input test image data representing the test image, and based on such comparison, the optimum noise filter setting for the printer/scanner pair is determined and stored for future use. This method is particularly useful for printing barcodes having high data capacity.

Vivek Pathak

Papers

Document management method using barcode to store access history information

Lossless data embedding with file size preservation

Method and apparatus for authenticating printed documents

Color barcode with enhanced capacity and readability for a closed loop system

Optimum noise filter setting for a scanner in a closed loop system