Image analysis – Applications
Reexamination Certificate
1999-05-27
2002-07-02
Johns, Andrew W. (Department: 2621)
Image analysis
Applications
Reexamination Certificate
active
06415041
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a digital watermark insertion system that converts information into a digital watermark and then inserts it in an image.
Conventionally, this type of digital watermark insertion system is disclosed, for example, in JP-A-No. 191394/1997 or the literature, “IEEE TRANSACTIONS ON IMAGE PROCESSING”, VOL. IP-6, No. 12, 1997, pp 1673-1687 and is designed to embed copyright information in digital signals creating audio and images.
FIG. 10
shows a conventional digital watermark inserter disclosed in the above-mentioned references. This inserter implements a DCT (Discrete Cosine Transform) or DFT (Discrete Fourier Transform) to input images and then outputs a transform coefficient to the mark inserter
1001
. The mark inserter
1001
inserts a digital watermark signal in the transform coefficient output from the frequency converter
1000
, with the digital watermark strength to be input. The inverse frequency converter
1002
subjects the watermarked transfer coefficient from the mark inserter
1001
to the inverse conversion opposite to the conversion by the frequency converter
1000
and then creates a watermarked image.
In operation, the frequency converter
1000
subjects all input images to the DCT or DFT process and then outputs the resultant transfer coefficients to the mark inserter
1001
. The mark inserter
1000
also selects N transfer coefficients with the same digital watermark length in the transfer coefficient decreasing order and inserts a digital watermark in them. Specifically, a digital watermark is inserted according to the following formulas:
(formula 1)
v′=v+&agr;x
or
(formula 2)
v′=v(1+&agr;x)
where x represents a digital watermark signal; &ngr; represents an embedded transfer coefficient; &agr; represents a digital watermark strength; and &ngr;′ represents a watermarked transfer coefficient.
The inverse frequency conversion circuit
1002
subjects the resultant watermarked coefficient to the inverse DCT or inverse DFT process and then creates a watermarked image.
The image-quality degradation of a watermarked image and a digital watermark resistance against attacking are in a tradeoff relationship. Both the factors are balanced by adjusting the digital watermark strength &agr; input to the mark inserter
1001
. As &agr; increases, the image-quality degradation of a watermarked image becomes large but the attack resistance property increases. On the contrary, as &agr; decreases the image-quality degradation of a watermarked image can be suppressed but the attack resistance property decreases.
However, the above-mentioned digital watermark insertion system has the disadvantage in that it is difficult to properly set the digital watermark strength.
The difficulty comes from the fact that a user inconsiderately adjusts the digital watermark strength to insert a digital watermark. The conventional digital watermark insertion system does not include means for recognizing either how degree a possible image-quality degradation caused by digital watermark insertion is or how degree the resistant property against attacking is. Hence, the user can decide an optimum digital watermark strength only after the image-quality degradation caused by digital watermark insertion has been actually tried over plural digital watermark strengths. If the user does not try attacking, the attack resistance cannot be accurately evaluated.
A proper digital watermark strength greatly depends on the content of an image. Hence, the problem is that even if the relationships between digital watermark strength, image-quality degradation and resistant property against attacking are decisively shown to the user, it is difficult to apply the relationships to all images so that the resultant strength is different from the truly optimum digital watermark strength.
SUMMARY OF THE INVENTION
The present invention is made to solve the above-mentioned problems.
The objective of the invention is to provide a digital watermark insertion system that can automatically decide digital watermark strengths based on constraints and image features by a user.
Moreover, another objective of the present invention is to provide a digital-watermark-characteristic table creating device that can automatically decide digital watermark strengths based on constraints and image features by a user.
The objective of the present invention is achieved by a digital watermark insertion system, wherein digital watermark information is inserted in an image, comprising means for calculating feature values of input images, classifying the input images into categories with the feature values, and outputting a category index; storage means for storing digital watermark characteristic tables according to predetermined various category indexes, each of the tables describing relationships between digital watermark strength, image-quality degradation degree and attack-resistant evaluation value, selecting a digital watermark characteristic table according to the category index of an input image, and outputting an image-quality degradation degree corresponding to an input digital watermark strength and an attack-resistant evaluation value, digital-watermark-strength calculation means for outputting the digital watermark strength to the storage means, and deciding and outputting an optimum digital watermark strength using digital-watermark-strength constraint information to be input based on the image-quality degradation degree and the attack-resistant evaluation value output from the storage means; and means for converting embedded data to be input into a digital watermark, inserting the digital watermark into the input image, with the optimum digital watermark strength acting as an input parameter, and outputting it as a watermarked image.
In the digital watermark insertion system according to the present invention, the digital-watermark-strength constraint information is a permissible critical value of an image-quality degradation degree. The digital-watermark-strength calculation means decides an optimum digital watermark strength within a range over which an image-quality degradation degree is less than the permissible critical value of the image-quality degradation value.
In the digital watermark insertion system according to the present invention, the digital-watermark-strength constraint information is a critical value of a safety index to attack. The digital-watermark-strength calculation means decides an optimum digital watermark strength within a range where an attack resistant evaluation value is more than the safety index critical value.
In the digital watermark insertion device according to the present invention, the digital-watermark-strength constraint information is a weighting index deciding a balance between an image-quality degradation degrees and a safety index. The digital-watermark-strength calculation means decides a contribution ratio by the weighting index, the contribution ratio at which the image-quality degradation degree and the safety index contributes to decide an optimum digital watermark strength.
According to the present invention, the digital watermark insertion system further comprises digital-watermark-characteristic table creation means for creating a digital watermark characteristic table describing relationships between digital watermark strength, image-quality degradation degree and attack-resistant evaluation value and for inputting a created digital watermark characteristic table to the storage means.
Moreover, according to the present invention, the digital watermark insertion system, wherein the characteristic table creation means, comprises digital watermark insertion means for converting embedded information to be input into a digital watermark, and inserting the digital watermark into an input image, with a digital watermark strength to be input, whereby a watermarked image is created; attacked-image creation means for attacking the watermarked image with an attack strength, according to an at
Miyamoto Yoshihiro
Oami Ryoma
Ohta Mutsumi
Johns Andrew W.
Nakhjavan Shervin
Scully Scott Murphy & Presser
LandOfFree
Digital watermark insertion system and digital watermark... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Digital watermark insertion system and digital watermark..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Digital watermark insertion system and digital watermark... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2867059