Image analysis – Image compression or coding
Reexamination Certificate
1998-09-01
2002-06-11
Boudreau, Leo (Department: 2621)
Image analysis
Image compression or coding
C382S100000, C380S054000, C380S201000, C705S057000, C713S176000
Reexamination Certificate
active
06404926
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method of processing an image data, a transmission medium and a recording medium. In particular, the present invention relates to an apparatus and a method of processing an image data, a transmission medium and a recording medium, capable of reading an accompany information much accurately.
2. Description of the Related Art
There is a technology, for a specific image data (a still image or a motion image sequence), which adds an information accompanied therewith into an image data, detects and utilizes the accompany information at a time when reproducing. As a representative example thereof, an addition of a copyright information is given.
When an unspecified (a general) user can utilize a specific image data, it is necessary to add a copyright information into the image data in advance in order that a person having a copyright for the image asserts the right thereof. By adding the copyright information, it makes possible to take steps of not displaying the image data when the copyright information indicating the image data to be not displayed is detected in the reproducing apparatus of the image or during the procedures in the reproducing method.
The above-mentioned addition or detection of the copyright information is, at a present time, well utilized for preventing an unauthorized duplication of videotape and the like. Recently, there exist many video tape rental shops, but if many users had enjoyed the video tapes by making the unauthorized duplications of the video tapes that they have rented by a low fare from the rental shops, the damages of the persons having the copyright of the video tapes and the video rental shops would be very bad.
Since an image data is recorded analogously in videotape, an image quality will be a little degraded when duplicating. As a result, when the duplications have been made several times, it becomes very difficult to maintain the image quality that has been held originally.
In contrast, in the devices that record and reproduce the image data digitally, the damage caused by the unauthorized duplication could be much worse. That is, in the devices that dealt with the image data digitally, there is no degradation of the image quality by duplication, in principle. As a result, the prevention of the unauthorized duplication in the devices that process digitally is far important than the one in analogue.
There are two methods of adding the information accompanied with the image data into that image data.
A first method is a method of adding into an auxiliary part of the image data. For example, in the videotape, as shown in
FIG. 18
, an auxiliary information of that image data is recorded in an upper part of the screen (the auxiliary part) which is substantially not displayed on the display screen. It is possible to add an accompany information, by utilizing a part of this area.
A second method is a method of adding into a-main part (a part to be substantially displayed) of the image data. This is, as shown in
FIG. 19
, the one that adds a specific pattern (WaterMark) to a part of or an entire image, with a degree of not visually sensible. As a concrete example thereof, there are a spectrum diffusion and the like that implement an addition or a detection of the information, by utilizing a key pattern which is generated using random numbers or M-series and the like.
In the following, an example of an addition or a detection an accompany information to the main part of the image data when using a watermark pattern. The concrete examples are shown in
FIGS. 20-23
.
Assuming to use the watermark pattern corresponding to the pixels of 4n×4n, as shown in FIG.
20
. The watermark pattern takes either a plus or a minus of 2 symbols for each pixel.
The watermark pattern preferably takes either one of 2 symbols at random, and a shape and a size of that area are optional.
When adding the watermark, an area whose size is equal to the size of the area of the watermark is set on the image subjected to implement the addition. By checking the area being set against the watermark pattern in superimposition, the value a is added to a pixel to which a plus symbol corresponds, and the value b is subtracted from a pixel to which a minus symbol corresponds. The values a, b might be arbitrary values, but they should be kept as constants throughout the watermark pattern thereof.
In the examples of
FIGS. 21-23
, a=1, b=1 are set, and as shown in
FIG. 21
, when all pixel values in the area subjected to implement the addition are 100, the pixel values of 101 and 99 are formed by an embedding operation which corresponds to the watermark.
When detecting the watermark, an area whose size is equal to the size of the area of the watermark is set on the image subjected to implement detection. A value of which all of the pixel values of this area are summed up is used as an evaluation value. When summing all of the pixel values, an addition is applied for a pixel to which a plus symbol corresponds, and a subtraction is applied for a pixel to which a minus symbol corresponds, by checking the area being set against the watermark pattern in superimposition. In the example of
FIG. 22
, a pixel of the pixel value 101 is added, and a pixel of the pixel value 99 is subtracted, and the calculated results thereof are added. At this moment, the watermark can not be detected correctly unless using the pattern that is the same as the watermark pattern used for adding the watermark. According to the detection operation described above, for example as shown in
FIG. 22
, the evaluation value at a time when the watermark is added turns to be (4n){circumflex over ( )}2 (the same as the numbers of pixels included in the area), and as shown in
FIG. 23
, the evaluation value at a time when no watermark is added turns to zero (0).
When the area of the watermark pattern is a quite large, and the watermark pattern is sufficiently at random, the evaluation value at a time when no watermark is added turns to be almost zero all the time. As a result, when the evaluation value exceeds a certain threshold, it might be evaluated as the watermark being added. According to the procedures described above, it makes possible to add a binary information (1 bit) of whether or not the watermark is added. When it is desirable to add more information, the information of the 2{circumflex over ( )}k ways (k bits) can be added by dividing the whole image into the k-areas and according to a method of processing such as respectively implementing the above mentioned operations.
As a watermark pattern, the one that is generated by using, for example, the M-series can be utilized. The M-series (the longest code series) is a sequence of numbers consisting of the binary symbols of 0 and 1, and the statistical distributions of the 0 and 1 are constant, and the code correlation is 1 at the origin, and is inversely proportional to the code length at other points. Of course, a watermark might be generated by a method other than the M-series.
When recording and reproducing. the image data digitally, it is a common practice to compress the data because an amount of information thereof becomes quite large if being kept as it is. As a method of compressing the image data, the low bit rate coding methods, such as the JPEG (Joint Photographic Experts Group) (color still image coding method), or the MPEG (Moving Picture Experts Group) (color motion image coding method) and the like are internationally standardized and turned to be in practical use. In the following, as an example, considering to compress the image data by the low bit rate coding, a structural example of an addition and a detection of an accompany information will be described.
In
FIG. 24
, a configuration of an encoder is shown. In the image data inputted, at first, in the watermark adding device
1
, an accompany information signal f is referred. Referring to this accompany information signal f, it is decided whether or not a process of a
Miyahara Nobuyoshi
Yagasaki Yoichi
Boudreau Leo
Frommer William S.
Frommer & Lawrence & Haug LLP
Kassa Yosef
Polito Bruno
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