Watermark

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Watermark

An image in a piece of paper that may be seen more clearly when it is held up to light. This is used in printing some money and passports to prevent counterfeiting. For example, if one holds a $20 American bill up to light, one would see a watermark of Andrew Jackson's face.
References in periodicals archive ?
Table 2-3 show the similarity between the original watermark and the extracted watermark after the watermarked images is attacked by JEPG compression, Gaussian noise and Salt & Pepper noise.
Finally, Calculate the watermarked matrix using U, V and [W.sub.img2] = U x [S.sub.6] x V'.
A watermarked data may undergo certain types of attacks before being reached to the detector or extractor.
The extracted watermark is comparable with original watermark and the comparability is able between original image (host image) and watermarked image as long as visually recognizable pattern as watermark has been used.
Another protocol attack is the copy attack; instead of destroying the watermark, the copy attack estimates a watermark from watermarked data and copies it to some other data, called the target data.
Finally, inverse DWT (IDWT) of the associated results obtained above to obtain the watermarked image: X = IDWT(Y ).
When the watermarked data is checked, the watermark is extracted using a unique key associated with the source, and the integrity of the data is verified through the integrity of the extracted watermark.
In addition to maintaining good quality of the watermarked image, this method also has sufficient resistance against destruction.
Separating the hidden watermark from the cover text is very difficult due to the fact that watermarked text is invisible for everyone except the original owner.
Britannia watermark shows a large oval enclosing a seating crowned lady (Britannia) who holds a flower in one hand and supports a spear by the other hand By Sheikha Al-Loughani KUWAIT, April 18 (KUNA) -- Since early days of the state, Kuwaiti leaders and officials tapped all means to protect official documents and manuscripts from counterfeit, watermarked papers was most common among them.
A watermark can be produced by applying this property.This watermark can be decoded further even after the watermarked image has undergone extensive geometric distortions, such as scaling and rotation.