watermark

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watermark:

see paperpaper,
thin, flat sheet or tissue made usually from plant fiber but also from rags and other fibrous materials. It is used principally for printing and writing on but has many other applications. The term also includes various types of paperboard, such as cardboard and wallboard.
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Watermark

 

a picture in a piece of paper, visible when the paper is held up to the light; it is formed during the process of making the paper.

Watermarks began to appear in Europe in the 13th century, and in Russia in the second half of the 17th century. The study of watermarks and the determination of the exact place and time of the making of a piece of paper are very important for the correct interpretation of a source.

Since 1723, Russia, following the example of other European countries, impressed watermarks on stamped paper (a depiction of the state coat of arms and the words“stamped paper”) in order to avoid counterfeiting of official documents and currency. Watermarks are usually made on paper at precise intervals, or they cover the whole field of the paper in the form of a repeated drawing or pattern. They can be used to distinguish genuine money, valuable papers and documents, and stamps from counterfeit items. Watermarks are also used as a means of ornamenting paper. The imprinting of watermarks is usually done with a dandy roll or with cylinders of a cylinder paper-making machine on a wet web of the paper.

N. M. BOKAREVA

watermark

[′wȯd·ər‚märk]
(graphic arts)
A localized modification of the structure and opacity of a sheet of paper so that a pattern or design can be seen when the sheet is held to the light.

digital watermark

A pattern of bits embedded into a file that is used to identify the source of illegal copies. For example, if a digital watermark is placed into a master copy of an audio CD or DVD movie, then all copies of that disc are uniquely identified. If a licensee were to manufacture and distribute them in areas outside of their authorized territories, the watermark provides a trace.

The watermark developer has to find creative ways of altering the file without disturbing it for the user. It is difficult to embed a watermark within an ASCII file, which is just raw text. However, it is relatively easy to alter a few bits within audio, video and image formats without making a noticeable difference on playback or display.


WinZip's Watermark Function
The popular WinZip utility performs numerous functions beyond simply encrypting a file. This is the dialog showing options for adding a digital watermark to certain image files. See WinZip.
References in periodicals archive ?
--False positive bit rate, [P.sub.fp], was calculated by applying original (unwatermarked) music clip the proposed detector, and average false positive for the the 20 audio clips used for performance evaluation was calculated to be 2.9 x [10.sup.-4].
Bob computes a counterfeit original [I.sub.B] = [I.sub.w] - [W.sub.B] and claims [I.sub.B] to be his "original" (unwatermarked) image and [W.sub.B] to be the watermark.
Figure 4 shows example images from such an attack: (a) is an original, unwatermarked image; (b) and (c) area watermarked version and a counterfeit, or forged original, respectively.
In almost all watermarking algorithms, the watermark embedding is performed in a host image which is stored in a storage system, such as device memory, and after watermarked image is generated, the original unwatermarked host image remains in the storage system.
This approach is used commercially for journalists to inspect digital pictures from a photo-stockhouse before buying unwatermarked versions.