Abstract:
A method of digital watermark embedding and extracting and device thereof in the text images of black-and-white binary value are disclosed. The embedding method includes: locating the regions of effective characters in the text image, grouping the regions of effective characters to account the number of black spots in each region, calculating the first pixel number needed to turn off in each character region according to the relative relationship of the number of black spots in each character region of each group, watermark information bit strings, and the first step length, and overturning the pixels in each region according to the first number. The extracting method includes: locating the regions of effective characters in the text image, grouping the regions of effective characters to account the number of black spots in each character region, extracting the embedded watermark information bit strings according to the relative relationship of the number of black spots in the character regions of each group and the first step length. The invention can better resist the attack of printing, scanning and copying, which has good visual effects and a lot of embedded information, and it has the better commonality in the field of digital printing.
Abstract:
Machine readable data is digitally watermarked into banknotes (16). Such watermarking can be optically sensed (13) and detected by various devices (11). In response, such devices (11) can intervene to prevent banknote reproduction. This arrangement addresses various problems, e.g., the use of digital image editing tools to circumvent other banknote anti-copy systems.
Abstract:
A method is provided for enabling identification of portions of a printed document from among a plurality of other portions which comprises the steps of: (i) providing a plurality of portions comprised in the printed document; (ii) selecting a first portion associated with the printed document; (iii) carrying out a comparative analysis between the first portion and at least one other portion selected from among the plurality of portions; (iv) based on the analysis results, determining a similarity factor for the selected first portion; and (v) if the similarity factor of the first portion is lower than a pre-defined value, allowing the association of one or more identification marks within that first portion.
Abstract:
A framework is provided for reducing the number of locations modified when hiding data, such as a digital watermark, in binary data. The framework complements data hiding techniques, such as digital watermarking techniques. After determining potential embedding locations according to an underlying technique, a data structure is created with values associated with those locations. A parity calculation is performed on the values in the data structure. The calculated parity is compared with hidden data to determine locations for modifications. Manipulations are then performed to reduce the total number of modifications needed to represent the hidden data. Modifications are made to the binary data according to the underlying technique. During decoding of the hidden data, the same locations can be determined, the same data structure can be created with the modified values, and a parity calculation is then performed to decode the hidden data.
Abstract:
The present invention is directed to watermarking an image using the highest practical watermark intensity that can be used without creating visual artifacts. With the present invention, an image is divided into areas. The size and shape of each area are determined so that each area only contains portions of the image where it is appropriate to use a watermark signal having the same energy (A). Some images consist of a series of lines. Such images are often used as the background image on security documents or currency (A). If an image consists of a series of lines, the invention can be applied by dividing the image into areas where the lines that form the image are within a certain range of widths (Tile). An appropriate watermark intensity is then determined for each such area and a watermark of this intensity is applied to the image. If an image is a grayscale image, areas having the same tonal value or tonal density are determined directly, or the image is transformed into a line art image and areas with the same size binary valued areas (lines, dots, squares, etc.) are selected by filtering the image. After the image has been divided areas which have a line width or tonal density value that is within a certain range of values, an appropriate watermark energy level is assigned to each area. The image is watermarked by changing the value of each bit or pixel in the image by an amount determined by both the value a payload tile and the intensity value associated with the area in which the bit or pixel lies.
Abstract:
Each copy (19) of software, such as software used by a digital computer (3) to create a document and the software used by printers (47), facsimile machines (77) or digital copiers (61) to produce or reproduce documents, is assigned a unique identifying code pattern (27) which is printed on all documents (19) produced with that software by a high resolution printer. The unique identifying code pattern (27) is a plurality of spaced apart marks (29) having a size no greater than about 150 dpi and preferably about 300 dpi, and is therefore, at best, barely noticeable to the human observer. The "invisible signature" permits detection of documents (19) made by unauthorized copies of software or by unauthorized or improper use of authorized copies. Preferably, the unique identifying code (27) is replicated multiple times (271-275) over the document (19) using an error correcting code to assure that at least one replication will be clear of matter selected for printing by the software. A high resolution scanner (21) extracts and identifies the code patterns (271-275) printed on the document (19). In systems (1) where the software generates a print file (11) for the high resolution printer, print commands for the pattern replications (271-275) are interspersed with the other print commands making identification and removal of the commands very difficult and not worth the effort since the "invisible signature" does not prevent copying of the software or noticeably detract from the appearance of the finished document (19).
Abstract:
A system for generating secure documents includes a station for generating a plain document and a security image generator that generates a security image. The security image is then incorporated into the plain document. Each security image consists of a plurality of secure elements, each secure element being defined by two sets of parallel lines. Each secure element defines an alphanumeric character or other unique image that is visible only under certain conditions, i.e., when inspected through a viewer. The technique can also be used to provide security images on a web page as a means of indicating that the web page is genuine.