Image analysis – Applications
Reexamination Certificate
1999-11-17
2004-08-10
Boudreau, Leo (Department: 2621)
Image analysis
Applications
Reexamination Certificate
active
06775391
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an associated information adding apparatus and method for adding information associated with image data, such as a still image or a moving image sequence, as an electronic watermark (watermark) into the image data, and an associated information detecting apparatus and method for detecting the associated information. The invention also relates to an illegal use preventing system using the associated information adding apparatus or method and the associated information detecting apparatus or method.
2. Description of the Related Art
There is a technique in which information associated with arbitrary image data (still image or moving image sequence) is added to the image data, and the associated information is detected at the time of reproduction and is used. As a typical usage example of this technique, it is possible to make mention of addition of copyright information.
In the case where any unspecified user can use specific image data, it is conceivable that a person having copyright on the image adds copyright information previously into the image data in order to assert the right. By adding the copyright information, in the case where the copyright information to instruct a user that the image data are unable to be displayed is detected in the processing procedure of a reproducing apparatus or reproducing method of the image, it becomes possible to take such a countermeasure that the image data are not displayed.
At present, the foregoing addition or detection of copyright information is used in the illegal copying preventing function of a videotape of analog recording (a video signal is recorded in a state of an analog signal) and the like. This function makes it impossible to illegally copy a videotape obtained through a method such as borrowing from a rental agent, and the right of a person having the copyright of the videotape is protected.
In the case of a videotape of analog recording, since image data are recorded in an analog manner, the picture quality is deteriorated when copying is performed. On the contrary, in an apparatus for recording and reproducing image data in a digital manner, which has recently come into wide use, the picture quality is not deteriorated by copying in principle, and even a number of repetitions of copying can be made without deterioration of the picture quality. Thus, the damage by illegal copying with an apparatus for performing the processing in a digital manner becomes more serious than the case of an analog apparatus, and prevention of illegal copying in the apparatus for performing the processing in a digital manner becomes very important.
As methods of adding information associated with image data, such as the foregoing copyright information, into the image data, there are mainly two methods.
The first method is a method of adding information into an auxiliary portion of image data. The auxiliary portion of image data indicates a portion other than the image data in an effective screen region. For example, it is a vertical blanking period of an analog video signal, a header portion or an additional data portion of a digital video signal, or the like. Actually, in an analog videotape, auxiliary associated information of image data is added to a part of a vertical blanking period.
The second method is a method of adding information into a main portion of image data, that is, the image data in an effective screen region. In this method, some specific pattern is added to all or a part of an image to such a degree that it can not be visually sensed. This is called an electronic watermark processing. As a specific example of this, there is a spectrum diffusion or the like in which addition and detection of information is performed by employing a key pattern produced by using random numbers, M-sequence, etc.
Since the first method adds information into an auxiliary portion of image data, that is, a place different from the contents themselves of the image, there is a problem that if the auxiliary portion is once separated, the added information is lost.
On the contrary, the electronic watermark processing is a processing for embedding information as noise existing in image data and being an unimportant portion for the perception of a human being. The information embedded in the image data by such electronic watermark processing (hereinafter, the information embedded by means of electronic watermark is referred to as a “watermark”) is added to the same frequency region and time region as the image data, so that it is hard to remove the information from the image data. On the other hand, there is a feature that even after filtering processing or data compression processing is performed for the image data, the watermark embedded in those can be detected from the image data.
The present application relates to an invention using a watermark as a method of adding associated information into a main portion of image data, which is the second method having the features as set forth above.
First, the outline of an adding and detecting system of a watermark will be described with reference to
FIGS. 1
to
4
.
FIG. 1
shows an example of a watermark pattern WM. The watermark pattern WM of this example has a size of vertical×horizontal=4n pixels×4n pixels (n is a natural number), and such a pattern that either one of two symbols +1 and −1 is taken for each pixel is designed to be used as shown in the drawing. In actual usage, it is preferable that the watermark pattern takes either one of the two symbols at random. The shape and size of a region of the watermark pattern are arbitrary.
When associated information is added to an image, a region having the same size as a region of a watermark pattern to be added is set on the image as an object for which the addition is performed. The set region and the watermark pattern WM are overlapped with each other to be checked, a value “a” is added for a pixel corresponding to the symbol of +1 in the watermark pattern WM, and a value “b” is subtracted for a pixel corresponding to the symbol of −1. Here, the value “a” and the value “b” can take arbitrary values.
FIG. 2
shows an example of addition of the watermark pattern WM into an image. In this example, every pixel value in a region of an image Pi as an object to which the addition is performed is 100, and a=1, b=−1 are set for the watermark pattern WM to be added. In an image Po obtained as a result that an embedding operation of this watermark pattern WM is performed, the pixel values are divided into 101 and 99 as shown in the drawing.
When associated information is detected, a region having the same size as the region of the watermark pattern WM is set on the image as an object to which detection is performed. An evaluation value as to correlation between the set image region and the watermark pattern WM is found. In this case, the sum for all pixels of the set image region is used as the evaluation value.
Specifically, when all pixels are summed to find the evaluation value, the set image region and the watermark pattern WM are overlapped with each other to be checked, addition is applied to the pixels of the symbol of +1 in the watermark pattern WM, and subtraction is applied to the pixels of the symbol of −1. At this time, detection is made by using the same pattern as the watermark pattern used when the associated information is added.
FIG. 3
is a view for explaining calculation of the evaluation value in the case where the watermark is detected from the image Po to which the watermark pattern WM was added in the manner as shown in FIG.
2
. In this example of
FIG. 3
, the evaluation value becomes (4n)
2
(equal to the number of pixels contained in the region).
On the contrary, the image Po of
FIG. 4
shows a case where the watermark pattern WM is not added, and the evaluation value of correlation to the watermark pattern with respect to this image Po becomes 0.
Actually, although it hardly o
Hosaka Kazuhisa
Miyahara Nobuyoshi
Yagasaki Yoichi
Akhavannik Hussein
Boudreau Leo
Frommer William S.
Frommer & Lawrence & Haug LLP
Simon Darren M.
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