JP2000138815A - Information imbedding device and imbedded information decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an information imbedding device and the imbedded information decoder, where large amounts of watermark information can be imbedded in a natural image, in a state which recognized can not be visually, and the watermark information can be decoded even in the absence of position information of the imbedded watermark information. SOLUTION: An block-specifying section 107 capable of imbedding in the information imbedding device 100 checks whether or not the number of '1s' included in a block consisting of 8 pixels for each bit plane of an original image satisfies a prescribed condition, and an imbed processing section 108 imbeds the components of the watermark information that is converted into 8-bit data, whose number of '1s' satisfies a prescribed condition by a conversion section 106 to the block-satisfying the condition. An imbed block specifying section 113 in the imbed information decoder 101 specifies blocks whose number of '1s' satisfies the prescribed condition, an extract processing section 115 extracts the blocks as 8-bit data and an inverse conversion section 116 applies inverse conversion to the data to components of the original watermark information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information embedding apparatus for embedding information to be concealed, such as copyright information, in image data in an invisible state, and an embedded information restoring apparatus for restoring the embedded information. .

[0002]

2. Description of the Related Art In recent years, due to the high performance and low cost of hardware such as personal computers, and the spread of networks involving a large number of subscribers represented by the Internet, individuals have created copyrighted works and made them available to many people. Opportunities have increased. At the same time, illegal use and tampering of copyrighted works have been observed, and copyright protection technology has become important. Among them, a digital watermarking technique for embedding and embedding signature data or the like as a watermark in image data itself has attracted attention because it is strong in information falsification and secondary processing.

The digital watermarking technique embeds other information as a watermark in a redundant portion that is not important to human vision, such as high-frequency components in image data, and various techniques are being studied from the viewpoint of its effectiveness. Until now, digital watermarking technology has been developed in the direction of how to effectively embed information and withstand secondary processing such as image processing.
Recently, a technology for embedding much more information in images such as natural images than in the past has been developed (Niimi et al .: "Image deep encryption using region segmentation by complexity", IEICE Tech. Report, IE97-14 (1997-
5), Nozaki et al .: "On a large-capacity Steganography method using natural images as dummy data", IEICE Technical Report, IE97-43, PRMU97-
74, MVE97-59 (1997-07)).

[0004] These embedding techniques make use of the characteristic that a complicated part in a natural image is not apparent even if it is replaced with another complex data. With eight pixels as the minimum unit block, if each block satisfies a complexity criterion defined under certain conditions, the watermark information is converted into a complicated pattern and embedded in that block.

[0005] These techniques make it possible to embed a large amount of watermark information while maintaining the same visual appearance as a natural image.

[0006]

However, in the above-mentioned conventional technology, a map file for recording the position where the watermark information is embedded is required, and at the time of restoration, the watermark information is extracted based on the map file. become. Of course, this map file will be different for each image. This causes a very troublesome operation, and greatly hinders the practical use of the digital watermarking technology.

For example, consider a case in which the above-described conventional technology is applied to a copyright management system shown in Nikkei Electronics (2-24, 1997, No. 683, p. 112). Here, the copyright management system is the following system. The copyright owner A is given an ID number from the copyright management company B, and uses the software for embedding the ID number when supplying the image created by himself to the third party C who has been given the right to use. Embed an ID number in the image. Another third party D who sees the image desires to use the image, and uses software for detecting an ID number to generate an ID from the image.
Take out the number and contact the copyright management company. Copyright management company B is the name of the copyright owner corresponding to the ID number,
Answer the contact information.

When the above-mentioned conventional information embedding technique is used in this system, in order for D to detect the ID number, not only general-purpose software for detecting the ID number but also the position where the ID number of the image is embedded is used. A recorded map file is required. Therefore, A sends a map file in which the position where the ID number is embedded is recorded to B together with the created image, and B manages the created image and the map file in association with each other. Since it is necessary to specify which image is present and to deliver the map file of the image to D, it becomes troublesome for all of A, B, and D.

The present invention has been made in view of the above problems, and an information embedding apparatus and an embedding method that do not require a map file recording a position where watermark information is embedded when restoring watermark information. An object of the present invention is to provide an information restoration device.

[0010]

In order to achieve the above object, the present invention provides an information embedding apparatus for embedding watermark information in image data, wherein a component of the watermark information has a total number of data that can be represented by n bits. 2 and the ⁿ of being represented using any particular conditions are satisfied the m (0 <m <2 ^n), representing the watermark information acquisition means for acquiring such watermark information, the image data Bit data on at least one bit plane of all bit planes is represented by n
Blocking means for blocking by bit, embeddable block specifying means for specifying a block satisfying the specific condition as an embeddable block from among the blocks, and the watermark information obtaining means for obtaining the specified block Data embedding means for replacing a component of the watermark information.

The present invention also relates to an embedded information restoring apparatus for restoring watermark information embedded in image data, wherein at least one bit plane on at least one bit plane of all bit planes expressing the image data is set to n.
Blocking means for sequentially blocking each bit, embedded block specifying means for specifying a block satisfying a specific condition among the blocks as an embedded block,
Data extracting means for extracting n-bit data in the specified block as a component of the watermark information.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) Embodiment 1 relates to an information embedding device for embedding watermark information in a natural image and an embedded information restoring device for restoring the watermark information.

FIG. 1 is a functional block diagram showing the configuration of an information embedding device and an embedded information restoring device. The information embedding device 100 embeds watermark information in a location in image data that satisfies a specific condition, and
In No. 01, since the position where the watermark information is embedded can be specified from the embedded image data itself, a map file for recording the embedded position becomes unnecessary.

The information embedding device 100 includes an original image storage unit 103 in which an original image such as a natural image to be embedded is stored, and copyright information to be embedded (represented by a sequence of 7-bit ASCII codes). Original watermark information storage unit 105 in which original watermark information such as a character string is stored.
A conversion unit 106 that converts the components of the original watermark information (one character represented by a 7-bit ASCII code) into components of the 8-bit data watermark information suitable for embedding according to the conversion table; And a block reading unit 104 that reads out each block in units of, and identifies the most characteristic part of the present embodiment as a block in which the number of 1s included in the block is 3 or more and 5 or less as an embeddable block. An embeddable block specifying unit 107, an embedding processing unit 108 for embedding a component (8-bit data) of watermark information in the embeddable block (8 pixels), and an embedded image storing an embedded image in which the watermark information is embedded From the storage unit 109 and the transmission unit 110 that delivers the embedded image via the Internet 102 It is made.

[0015] The embedded information restoring device 101 receives a post-embedded image from the Internet 102.
1, an embedded image storage unit 112 for storing the received embedded image, and a block reading unit 114 for reading the embedded image for each block of 8 pixels.
And an embedded block specification for specifying a block which is the most characteristic part of the present embodiment and in which the number of 1s included in the block is 3 or more and 5 or less as an embedded block in which components of the watermark information are embedded. Part 113,
Extraction processing unit 115 that extracts components of watermark information from embedded blocks (8 pixels) as 8-bit data
And an inverse conversion unit 116 that returns the components (8-bit data) of the extracted watermark information to the components (characters represented by 7-bit ACSII code) of the original watermark information in the original format according to the conversion table. An original watermark information storage unit 117 that stores the converted original watermark information, and an end determination unit 118 that determines whether a component of the original watermark information is a flag indicating the end of embedding.

FIG. 2 shows that the components of the original watermark information used in the conversion unit 106 and the inverse conversion unit 116 are integer values (0 to 255).
FIG. 4 is a diagram showing a conversion table 200 in the case of FIG. Conversion unit 1
06 converts the integer value (0 to 255) 201 which is a component of the original watermark information into 8-bit data 202 which is a component of the watermark information according to the conversion table 200. , The 8-bit data 202 which is a component of the watermark information is inversely converted to return to the integer value 201 which is a component of the original watermark information.

The 8-bit data 202 is classified into groups 203 according to the number of 1, for example, ₈ C ₀ , ₈
C ₁ represents 0, 1 and 1 respectively. The 8-bit data 202 is ordered such that data belonging to a group having a smaller number of 1s and data having lower bits in the same group in the same group correspond to a smaller number of integer values.

According to the conversion table 200, all integer values from 0 to 255, which are components of the original watermark information, can be converted into 8-bit data, which is a component of the watermark information. Only a specific group may be used as a component of information.
That is, in this embodiment, three groups 204 of ₈ C ₃ , ₈ C ₄ , and ₈ C ₅ in which the number of 1 is 3 or more and 5 or less are used. In this case, the range of the components of the original watermark information is limited to 37 to 218 (for 182). Therefore, when the components of the original watermark information are out of this range, it is necessary to normalize the components before the conversion in the conversion table.

In the present embodiment, the original watermark information
The component is a character represented by 7-bit ASCII code
Therefore, the 7-bit ASCII code and₈C_Three,₈
C_Four, ₈C_FiveOf 8-bit data belonging to the group
Injury is required. FIG. 3 shows the conversion unit 106 and the inverse conversion unit 11
7 is 7-bit ASCI
The conversion table 300 for the character represented by the I code
FIG. Here, the component 30 of the original watermark information
7-bit ASCII character 304 that is 1 (128 characters)
And an end flag 306 (for one) indicating the end of embedding
For the 8-bit data 302 which is a component of the watermark information,
The remaining (53 pieces) are unused 305
are doing.

FIG. 4 shows a state in which the data of the original image is represented by eight bit planes, and each bit plane is divided into blocks. That is, the original image 400 is horizontally 512
It is composed of pixels × 512 pixels and 8 bit planes, and the unit of the block is 4 pixels × 2 pixels of each bit plane. The block numbers are assigned in order from the 1-bit plane, and in the same bit plane, the numbers are assigned in order from the upper left of the image.

The original image 400 is read by the block reading unit 104 for each block in the order of the block number, and it is determined by the embeddable block specifying unit 107 whether it can be embedded. Is embedded. Therefore, the components of the watermark information are embedded in order from the appropriate block of the lower bit plane.

Here, the reason why the block unit is set to 8 pixels is to increase the amount of information to be embedded and to allow the information to be embedded in a normal CRT screen in a visually inconspicuous state. The reason why the components of the watermark information are embedded in order from the lower bit plane is that even if the lower bit plane is replaced with other data, the amount of change is small and thus it is not visually noticeable. For example, if the bit value of the 8-bit plane changes, the gray value of the image changes by 128, but even if the bit value of the 1-bit plane changes, only the gray value changes by 1.

FIG. 5A shows the relationship of data when watermark information is embedded in an original image, and FIG. 5B shows an image 520 after embedding. First, the conversion unit 106
The signature code (43-7A) which is the original watermark information
Each letter and end flag constituting a is converted to _{8 C 3, 8 C 4,} 8 C 8 -bit data values belonging to one of the ₅ 501-506.

Next, 8-bit data 110001000 501 which is a component of watermark information ('4' before conversion)
(7-bit ASCII code) is embedded as follows. The block reading unit 104 reads the first block 507 of the original image 400. The embeddable block identification unit 107 is configured to include 1
If the number of satisfies the embeddable condition of 3 or more and 5 or less, the block is regarded as an embeddable block. The reason why the block can be embedded is to embed the block in a visually indistinguishable state. Since the first block includes four 1s, it becomes an embeddable block, and the embedding processing unit 108 outputs the 8-bit data 1100010
00 501 is recorded as the first block 524 of the image after embedding.

Next, embedding of 8-bit data 11000010 502 (7-bit ASCII code of '3' before conversion), which is a component of watermark information, is performed as follows. The block reading unit 104 reads the second block 508. Embedding block specifying unit 1
In the case of 07, since the second block includes two 1 and does not satisfy the embedding condition, the block is not regarded as an embedding block. In this case, the second block 5 of the original image
08 is the second block 530 of the image after embedding as it is.
Becomes Then, the block reading unit 104 reads the next third block 509. The embeddable block specifying unit 107 sets the block as an embeddable block because the third block includes three 1s and satisfies the embeddable condition. The embedding processing unit 108 stores the 8-bit data 11000010 502 as the third block 525 of the image after embedding.

Similarly, 8-bit data 10100001503 (a 7-bit ASCII code of “-” before conversion), which is a component of the watermark information, is converted into a block # 1,1,0,0,0,1,1 of the original image. , 1} (510), the block of the image after embedding becomes {1, 0, 1, 0, 0, 0, 0, 1} (526). 8-bit data 001 as a component of watermark information
10011504 (Before conversion, 7-bit ASCI of 'A'
I code) is embedded in the block {0,1,0,1,1,0,0,0} (511) of the second bit plane without finding an embeddable block in the first bit plane. The block of the image after embedding is $ 0,
0, 1, 1, 0, 0, 1, 1｝ (527).

Similarly, 8-bit data 11100000 505 (7-bit ASCII code of “7” before conversion), which is a component of the watermark information, is embedded in the block 512 of the fifth bit plane, and the embedded image The corresponding block of {1, l, 1, 0, 0, 0, 0,
0｝ (528), which is 8 which is a component of the watermark information.
Bit data 11111000 506 (7-bit ASCII code of a character indicating the end before conversion) is embedded in block 513 of the fifth bit plane, and the block of the embedded image is {1,1,1,1,1,0}. , 0,
0｝ (529).

FIG. 6A shows the relation of data when watermark information is extracted from an image after embedding.
(B) is a diagram showing the extracted watermark information 500. The block reading unit 114 stores the post-embedded image 52
The first block 524 of 0 is read. The embedded block specifying unit 113 determines that the number of 1s included in the block is 3
When the embeddable condition of not less than 5 and not more than 5 is satisfied, the block is regarded as an embedded block. The first block 524 becomes an embedded block because it contains three 1s, and the extraction processing unit 115 extracts the data {1, 1, 0, 0, 0, 1, 0, 0} of the first block 524 and outputs the watermark. 8-bit data 110 as a component of information
00100 501 (return to 7-bit ASCII code of '4' by inverse conversion).

Next, the block reading section 114 reads the second block 530 of the image 520 after embedding. The embedded block specifying unit 113 does not set the second block 530 as an embedded block because the second block 530 includes two ones. Therefore, this block is not extracted by the extraction processing unit 115. The block reading unit 114 reads the third block 525 of the image 520 after embedding. The embedded block specifying unit 113 sets the third block 525 to 1
The embedded block is included because of the number. The extraction processing unit 115 outputs the data # 1,1,3 of the third block 525.
0, 0, 0, 0, 1, 0} are taken out, and 8-bit data 11000010 50 which is a component of the watermark information is extracted.
2 (return to 7-bit ASCII code of '3' by inverse conversion).

Hereinafter, similarly, the blocks 526 to 10100001 503 of the first bit plane (return to the 7-bit ASCII code of "-" by the inverse conversion)
Is extracted, and 00110011 504 (returned to the 7-bit ASCII code of 'A' by inverse conversion) is extracted from the second bit plane block 527, and the fifth bit plane block 528 to 110000 is extracted.
0 505 (7-bit ASCI of '7' by inverse conversion
The fifth bit plane block 529 is extracted, and 11111000 506 (returned to the 7-bit ASCII code of the specific character indicating the end by the inverse conversion) is extracted.

Next, the operation of the entire information embedding device according to the present invention configured as described above will be described. FIG. 7 is a flowchart showing the operation procedure of the entire information embedding device. First, the conversion unit 106 reads from the original watermark information storage section 104 and a signature code text which is a component of the original watermark information end flag one by one character, according to the conversion table shown in FIG. 4, ₈ C _{3, 8} C _{4, 8} C either data belonging to a group of _5, i.e., converts the number of 1 is 3 or more 5 or the following 8-bit data, and outputs the embedding processing unit 108 (step S700).

Next, the embeddable block specifying unit 107
Checks whether the number of the block from which the original image is to be read exceeds a predetermined value. In the present embodiment, since a 5-bit plane is embedded in order from a 1-bit plane, the block number is 32,768 (block / bit plane).
It is assumed that up to × 5 (bit plane) = 163,840 blocks are embedded (step S701).

When the block number from which the original image is to be read does not exceed the predetermined value, the embeddable block specifying unit 107 instructs the block reading unit 104 to read the block. Next, the next block of the original image is read out (step S702). Next, the embeddable block specifying unit 107
Counts the number of 1s included in the read block and checks whether the number of 1s is 3 or more and 5 or less (step S703). The number of 1s included in the block is 3 or more and 5 or less. If the number is less than or equal to the number, the component of the watermark information is embedded in that block of the original image. That is, the embedding processing unit 108
Records the components (8-bit data) of the watermark information converted in step S700 in the embedded image storage unit 109 as embedded image blocks. (Step S704).

If the number of 1s contained in a block is not more than 3 and not more than 5, no watermark information is embedded in that block of the original image. That is, the read original image blocks are stored in the post-embedded image storage unit 109 as they are as the post-embedded image blocks. For the components of the watermark information that have not been embedded, the process from step S701 described above is repeated, and the block to be embedded is specified and embedded in that block (step S705).

Next, the converter 106 checks whether all the components of the original watermark information have been read. If the reading has not been completed, the process returns to step S700 to embed the component (next one character) of the next original watermark information (step S706). When reading of all the components of the original watermark information is completed, the fact is notified to the block reading unit 104, and the block reading unit 10
4 reads out all blocks of the original image after the next block from the original image storage unit 103, and stores them in the embedded image storage unit 109 as they are as the remaining blocks of the embedded image (step S707).

The post-embedded image created in this way is transmitted from the transmitting unit 110 to a terminal connected via the Internet 102 at an appropriate time. Next, the operation of the entire embedded information restoring device according to the present invention will be described.
FIG. 8 is a flowchart showing an operation procedure of the entire embedded information restoring device. Embedded block specifying unit 113
Checks whether the number of the block from which the embedded image is read does not exceed a predetermined value (step S800). In the present embodiment, since the embedded information restoring device 101 knows in advance that the embedded data is embedded in the range from the 1-bit plane to the 5-bit plane, the predetermined value is the number of blocks 163 and 840 up to the 5-bit plane. .

If the block number from which the embedded image is read does not exceed the predetermined value, the embedded block specifying unit 113 instructs the block reading unit 114 to read the block, and the block reading unit 114 The embedded image received in step 111 and stored in the embedded image storage unit 112 is read out in block units (step S801).

Next, the embedded block specifying unit 113
The number of 1s included in the read block is counted, and it is checked whether the number of 1s is 3 or more and 5 or less. If the number of 1s included in the block is not 3 or more and 5 or less, the process returns to step S800 to check the next block (step S802). If the number of 1s included in the block is 3 or more and 5 or less, the extraction processing unit 115 extracts the block as 8-bit data, which is a component of the watermark information, and sends it to the inverse conversion unit 116 (step S803). ).

The inverse conversion unit 116 returns the 8-bit data to the components (signature code character or end flag) of the original watermark information according to the conversion table, and stores it in the original watermark information storage unit 117. (Step S804).
The end determination unit 118 checks whether the component of the original watermark information corresponds to the end flag, and in the case of the end flag, instructs the embedding block specifying unit 113 to end the restoration of the watermark information. If not, the process returns to step S800 to restore the next character (step S805).

As described above, the information embedding apparatus converts the components of the original watermark information into a block satisfying the condition that the number of 1s included in the block is 3 or more and 5 or less, and converts the component into a format that satisfies the above condition. Since the embedding is performed, the embedding information restoring device determines that the number of 1s included in the block is 3 or more
The embedding position of the watermark information can be specified only by judging from the image data only whether or not the condition of not more than the number is satisfied. That is, the information embedding device and the embedded information restoring device can embed a large amount of watermark information with a simple embedding rule without separately recording the embedding position in an inconspicuous portion existing in a large amount in image data. This is made possible by eliminating the need for a map file that records the watermark information embedding position for each image.

In this embodiment, the watermark information can be embedded from the 1-bit plane to the 5-bit plane. However, even if the image quality is impaired, if the embedding method is simplified, all the bits can be embedded. It may be embedded in a plane. In this embodiment, the image size is 512 horizontal pixels × 512 vertical pixels, the number of bit planes is 8, and the block size is 4 horizontal pixels × 2 vertical pixels. Although the watermark information is embedded, even for an image different from the watermark information, what bit plane and what condition are to be embedded in a block that satisfies the condition (parameter setting) is different from the present embodiment, but the same processing method as in the present embodiment is used. Can be applied. At this time, it may be determined which block of which bit plane is to be embedded from the frequency distribution of the number of 1s included in the block. For example, which bit plane is to be embedded is calculated from the average A (average of both ends) of the frequency of all 1 and 0 blocks and the average B of the frequency of the other blocks in the frequency distribution of 1 ( If (BA) is negative, the bit plane may be embedded, and if (BA) is positive, the bit plane may not be embedded.

Further, in this embodiment, the components of the watermark information are embedded in the blocks satisfying the condition of “3 to 5 in the block” uniformly for each bit plane. If it is desired to perform optimal embedding in consideration of the amount and the image quality after embedding, the conditions of the block to be embedded may be set for each bit plane.
For example, the watermark information may be embedded in all the blocks in the 1 to 3 bit planes, and only in the blocks in which the number of 1s satisfies the condition of 3 to 5 in the 4 and 5 bit planes.

The block to be embedded is determined by the block.
May be determined from the frequency distribution of one number included in the
No. The number n of 1s contained in the block consisting of N pixels
Cloth is_NC _nIf the distribution approximates to a certain extent,
Embedded in every block,_NC _nIf it deviates,
In the frequency distribution, the number of 1s with high frequency is in the middle range
May be embedded only in the block located at.

The present invention is not limited to a dedicated device.
Since the program can be executed by a general-purpose computer, the processing procedure of the present invention can be recorded on a medium as a program and distributed. (Consideration) Here, in the above embodiment, the bit planes that can be embedded are the first to fifth bit planes,
The grounds for setting the number of embeddable blocks to 1 to 3 to 5 will be described.

FIG. 9 is a diagram showing the frequency of each block including 1 for each bit plane in the flat area of the natural image. FIG. 10 is a diagram illustrating the frequency according to the number of blocks including 1 for each bit plane in the edge region of the natural image. In these figures, each bit plane of a certain natural image (8-bit grayscale image) is divided into a total of 8-bit blocks of 4 horizontal pixels × 2 vertical pixels, and 1 is N in 8 bits.
The case where the number is included is represented by (8 ConbiN).

The flat area and the edge area of the image were classified according to the following criteria. The change in the gray level of the image in the horizontal direction is 1
When the value exceeds 0% or the change in the vertical direction exceeds 10%, the pixel is regarded as an edge pixel. The block of each plane is an edge block when two or more edge pixels are included in the area, and the other blocks are flat blocks. A collection of flat blocks was defined as a flat area, and a collection of edge blocks was defined as an edge area. From these figures, the appropriate embedding position of the watermark information was examined as follows. (1) In both the flat portion and the edge portion about 1-3 bit plane, the distribution of these bit planes can be regarded as (the n number including 1) ₈ C _n follows a probability distribution. That is, the bit values of these bit planes can be regarded as noise components accompanying the quantization. Further, even if the bit values of these bit planes are changed, the change in the gray level of the image is small (1, 2,.
Or 4), visually indistinguishable.

Therefore, it can be said that these bit planes are suitable for embedding the watermark information. Also, since the watermark information can be embedded in any block regardless of the number of one block, the amount of information that can be embedded is large. Also, in order to match the embedding rule in a higher-order bit plane, even if the number of blocks to be embedded is limited to an intermediate block (3 to 5), the combination of ₈ C _n (n = 3 to 5) 182
It can be said that the amount of information that can be embedded can still be maintained because there are many pieces. (2) About 4-bit plane In the edge part, like the 1-3 bit plane, ₈ C
_Since it follows the probability distribution of _n (the number of n including 1), the watermark information can be embedded in all the blocks.

[0048] In the flat part, a little deviation from the ₈ C _n distribution,
It can be said that the characteristic components of the image are gradually appearing.
In this case, blocks of all 1's or 0's, or blocks close to this, are not suitable for embedding. On the other hand, an area where the number of 1s is intermediate (3 to 5) is regarded as a noise component, and it can be said that it is appropriate to embed watermark information in a block with the number of 1s being 3 to 5.

From the above, it is considered appropriate to embed watermark information only in blocks having 3 to 5 1s in this bit plane. (3) About the 5-bit plane In this bit plane, the probability distribution deviates from the probability distribution of ₈ C _n (the number including n is 1) and is no longer regarded as noise.

In the edge part, where the shading changes sharply, in such a place, a complicated block having 3 to 5 1s is replaced with a complex block satisfying the same 3 to 5 conditions. Not visually noticeable. Therefore,
It is appropriate to embed watermark information that satisfies the condition that the number of 1s is 3 to 5 in a block where the number of 1s is 3 to 5.

On the other hand, in the flat portion, the ratio of all 1 or 0 blocks is high, and it can be said that it indicates the correlation between adjacent pixels of the image, that is, an important feature component of the image. Further, it can be said that the change in density is more conspicuous in the flat portion and is not suitable for embedding as compared with the edge portion.
However, since the ratio of 1s is not high in the ratio of the intermediate blocks, it can be said that even if the watermark information is embedded in the intermediate blocks, the number of blocks to be replaced is small and it is not conspicuous.

From the above, it is considered effective to embed 3 to 5 pieces of watermark information in 1 to 3 to 5 blocks. (4) 6 to 8 Bit Planes In the distribution in these bit planes, the number of 1s is 0 and the frequency of 8 is high. That is, all blocks are either 0 or 1. This is these bit planes,
This indicates that the correlation between adjacent pixels of the image is strong. That is, it can be said that the bit values of these bit planes are important components indicating the features in the image. Further, when the bit values of these bit planes are changed, the change in the gray level of the image is large (32, 64, 128), and is visually noticeable. Therefore, embedding watermark information in these bit planes is not appropriate. However, if the watermark information is intentionally embedded in these bit planes in order to match the embedding rules with the lower bit planes, the blocks in which the number of 1s is intermediate (3 to 5) are the blocks in which the number of those blocks is small and replaced. Because of the small number, it can be said that it is not noticeable.

From the above examination, it is considered that the following embedding rules are effective. (1) From 1 bit plane to 5 bit plane,
In order from the lower bit plane, 3 to 5 pieces of watermark information of 1 are embedded in blocks satisfying the condition of 3 to 5 1s. As a result, it is possible to embed easily and maintain the image quality. (2) Embed watermark information from 1-bit plane to 8-bit plane. Other conditions are the same as (1).
Although the process is simple, embedding in a high bit plane may result in lower image quality. (3) From 1 bit plane to 5 bit plane,
The watermark information is embedded in order from the lower bit plane.
The block to be embedded is variable for each bit plane.
For example, it is assumed that the watermark information is embedded in all the blocks in the 1 to 3 bit plane, and only in the block in which the number of 1 satisfies the condition of 3 to 5 in the 4 and 5 bit plane. Processing becomes more complicated than in (1), but more information can be embedded.

Using the above method (1), an experiment was conducted in which three to five random numbers were embedded in two types of natural images. As a result, the natural image did not look different before and after embedding, and the effectiveness of the method was proved.
It is considered that the results of (2) and (3) reflect the respective advantages. The above consideration is based on the assumption that the image size is 512 horizontal pixels × 512 vertical pixels, the number of bit planes is 8, the block size is 4 horizontal pixels × 2 vertical pixels, and watermark information is added to the image displayed on the CRT. Although embedding is performed, similar considerations can be made for an image different from this.

At this time, it is necessary to consider which bit plane is to be embedded in which block from the frequency distribution of the number of 1s included in the block as shown in FIGS. Also, it is effective to apply the following rules. For example, to what bit plane to embed, the average A (the average of both ends) of the number of 1 and 0 blocks and the average B of the number of other blocks are all determined.
You can decide more. More specifically, if (B−A) is negative as in the 1 to 5 bit planes of FIGS.
If (BA) is positive, the bit plane may not be embedded like a bit plane.

[0056] Also, the embedded or to which the block, _N C _n
Can also be determined from the distribution of Specifically, the distribution of the number of 1s as shown in the 1 to 3 bit planes of FIGS.
_N C if you are approximated by a certain range in the _n-buried in all the blocks, the number of 1 when shifted from _N C _n be embedded only in the middle of the block (block showing high frequency in the frequency distribution) It may be.

[0057]

As is apparent from the above description, the present invention relates to an information embedding device for embedding watermark information in image data, wherein the component of the watermark information is 2 ⁿ data elements which can be represented by n bits. M (0
<M <2 ⁿ ), a watermark information acquisition unit that acquires such watermark information, and a bit on at least one bit plane of all bit planes that represent image data. Blocking means for dividing data into n-bit blocks; embeddable block specifying means for specifying, as an embeddable block, a block satisfying the specified condition from among the blocks; and watermark information obtaining means for specifying the specified block. And a data embedding unit that replaces the component of the acquired watermark information. As a result, the components of the watermark information are embedded in the blocks satisfying the specific conditions in the image. Therefore, the position where the watermark information is embedded in the image is not separately recorded as position information, and only the image data itself is recorded. Thus, an information embedding device capable of embedding the watermark information so that the position of the watermark information can be determined is realized.

Here, the specific condition can be characterized in that the number of 1s in the n bits is within a specific range. As a result, the watermark information is embedded only in the blocks in which the number of 1s in the image is within the specific range, and the position of the watermark information can be determined by simply checking whether the number of 1s in the image data block is in the specific range. An information embedding device that can embed watermark information so that it can be determined is realized.

Here, the specific range of the number of 1 is obtained by analyzing the frequency distribution of the number of 1 included in the block belonging to each bit plane of the image data prepared in advance, and determining the high frequency from the analysis result. It can be characterized in that a range of 1 is selected. As a result, the number of blocks that can be embedded can be maintained large, and the number of blocks having a high frequency is in the middle range, and in this range, the embedding is inconspicuous even by embedding. Can be embedded while maintaining the same identity.

Further, the specific range of the number 1 is individually determined for each bit plane of the image data, and the width of the number is narrowed from the lower bit plane to the upper bit plane. You can also. As a result, the range of the number including the block 1 to be embedded can be expanded in the low bit plane in which the embedding is not conspicuous, and the range of the number including the block 1 can be narrowed in the high bit plane that is conspicuous. This has the effect of effectively utilizing blocks that can maintain the same visual appearance.

Further, the embeddable block specifying means specifies the embeddable blocks in order from the lower bit plane to the upper bit plane, and the data embedding means replaces the specified block with a watermark information component. It can also be characterized by going. As a result, watermark information is embedded from a block that is visually inconspicuous even when the bit value changes, so that an information embedding device that can maintain a high degree of visual identity between images before and after embedding is realized.

Further, the embeddable block specifying means specifies the embeddable block for bit planes belonging to the lower order excluding a predetermined number of upper bit planes including the most significant bit plane. Can also. As a result, the watermark information is not embedded in the block where the difference is conspicuous when the bit value changes, so that the embedding of the watermark information can avoid an obstacle that the apparent identity of the original image is lost. There is.

According to the present invention, there is also provided an embedded information restoring apparatus for restoring watermark information embedded in image data, wherein at least one bit plane of all bit planes expressing the image data is n-bit data.
Blocking means for sequentially blocking each bit, embedded block specifying means for specifying a block satisfying a specific condition among the blocks as an embedded block,
Data extracting means for extracting n-bit data in the specified block as a component of the watermark information. With this, when image data in which watermark information is embedded in a block satisfying a specific condition in an image is given, the position where the watermark information is embedded in the image is specified only by the image data itself, and the watermark information is determined. Since the information can be extracted and restored, an embedded information restoring device that can restore the watermark information without the position information in which the watermark information is embedded is realized.

The present invention also relates to a computer-readable recording medium on which a program for causing a computer to embed watermark information in image data is recorded, wherein all components of the watermark information can be represented by n bits. number ^the 2 ⁿ satisfies a specific condition of m of (0 <m <
2 ⁿ ), obtaining such watermark information, and blocking n bits of bit data on at least one bit plane of all bit planes representing image data. Executing the steps of: converting a block satisfying the specified condition from the blocks as an embeddable block; and replacing the specified block with a component of the acquired watermark information. The program is characterized by recording a program to be executed. As a result, the watermark information can be embedded in a block satisfying a specific condition in the image, so that the watermark information can be embedded so that the position where the watermark information is embedded in the image can be determined only by the image data itself. Thus, a program executable by a general-purpose computer is realized.

According to the present invention, there is provided a computer-readable recording medium storing a program for causing a computer to restore watermark information embedded in image data, wherein at least one of all bit planes expressing the image data is stored. Step of sequentially dividing the bit data on the bit plane of n bits by n bits, identifying a block satisfying a specific condition from the blocks as an embedded block, and converting n bit data in the identified block into watermark information. Recording a program for causing a computer to execute the step of extracting as a component. This makes it possible to identify the position where the watermark information is embedded in the image only by the image data itself and extract and restore the watermark information. Therefore, even if there is no position information in which the watermark information is embedded from any image, the watermark information can be obtained. A program that can be extracted and can be executed by a general-purpose computer can be realized.

As described above, according to the present invention, watermark information can be embedded and restored even without the position information of the image in which the watermark information is embedded, whereby the copyright information and the like are embedded in the image for distribution and distribution. In a copyright protection system that restores copyright information from images,
The troublesome procedure of exchanging the position information of the image in which the watermark information is embedded becomes unnecessary, and its practical effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a configuration of an information embedding device and an embedded information restoring device according to a first embodiment.

FIG. 2 is a conversion table 2 used by the conversion unit 106 and the inverse conversion unit 116 when the watermark information is an integer value (0 to 255).
FIG.

FIG. 3 is a diagram showing a conversion table 200 used by the conversion unit 106 and the inverse conversion unit 116 when watermark information is a character represented by 7-bit ASCII.

FIG. 4 is a diagram illustrating a state in which data of an original image is represented by eight bit planes and each bit plane is divided into blocks.

FIG. 5A shows the relationship between data when watermark information is embedded in an original image, and FIG. 5B shows an image 520 after embedding.

FIG. 6A shows the relationship between data when watermark information is extracted from an image after embedding, and FIG. 6B shows extracted watermark information 500.

FIG. 7 is a flowchart illustrating an operation procedure of the entire information embedding device.

FIG. 8 is a flowchart illustrating an operation procedure of the entire embedded information restoring apparatus.

FIG. 9 is a diagram showing frequencies for each number of blocks including 1 for each bit plane in a flat region of a natural image.

FIG. 10 is a diagram illustrating frequencies according to the number of blocks including 1 for each bit plane in an edge region of a natural image.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 information embedding device 101 embedded information restoring device 102 internet 103 original image storage unit 104 block reading unit 105 watermark information storage unit 106 conversion unit 107 embeddable block specifying unit 108 embedding processing unit 109 embedded image storage unit 110 transmission unit 111 reception unit 112 Image storage unit after embedding 113 Embedding block specifying unit 114 Block reading unit 115 Extraction processing unit 116 Inverse conversion unit 117 Watermark information storage unit 118 End determination unit

Continued on the front page F term (reference) 5B057 AA20 CA16 CA18 CB16 CE08 CG07 DA17 DC19 5C076 AA16 AA40 BA07 CA10 5C077 LL14 MP05 MP08 NP05 PP23 PP27 PP58 PP68 PQ08 PQ12 PQ19 PQ22 PQ23

Claims (9)

[Claims] 1. An information embedding device for embedding watermark information in image data, wherein m (0 <m) components of the watermark information satisfy a specific condition among a total of 2 ⁿ data items that can be represented by n bits. <2 ⁿ ), a watermark information acquiring unit that acquires such watermark information, and a bit data on at least one bit plane of all bit planes that represent image data. blocking means for blocking by n bits, embeddable block specifying means for specifying a block satisfying the specified condition as an embeddable block from among the blocks, and the watermark information obtaining means obtaining the specified block An information embedding apparatus comprising: a data embedding unit that replaces a component of the watermark information. 2. The information embedding apparatus according to claim 1, wherein the specific condition is that the number of 1s in the n bits is within a specific range. 3. The specific range of the number of “1” is obtained by analyzing a frequency distribution of the number of “1” included in a block belonging to each bit plane of image data prepared in advance, and obtaining a high frequency from the analysis result. 3. The information embedding device according to claim 2, wherein a range of the number of the information embeddings is selected. 4. The method according to claim 1, wherein the specific range of the number of 1 is individually determined for each bit plane of the image data, and the width of the number is narrowed from a lower bit plane to an upper bit plane. The information embedding device according to claim 2, wherein 5. The embeddable block specifying means,
3. The embedding block is specified in order from a lower bit plane to an upper bit plane, and the data embedding unit replaces the specified block with a watermark information component. 4. Information embedding device. 6. The embeddable block specifying means,
3. The information embedding apparatus according to claim 1, wherein the embeddable block is specified for bit planes belonging to lower levels excluding a predetermined number of upper bit planes including the highest bit plane. 7. An embedded information restoring device for restoring watermark information embedded in image data, wherein bit data on at least one bit plane of all bit planes expressing the image data is sequentially blocked by n bits. Block-forming means, embedded block specifying means for specifying a block satisfying a specific condition from the blocks as an embedded block, and data extracting means for extracting n-bit data in the identified block as a component of watermark information. An embedded information restoring device, comprising: 8. A computer-readable recording medium on which a program for causing a computer to embed watermark information in image data is recorded, wherein a total number of data elements in which watermark information can be represented by n bits is 2 ^n. M satisfying a specific condition (0 <m <2 ⁿ )
Obtaining such watermark information, and blocking n bits of bit data on at least one bit plane of all bit planes representing image data. A program that causes a computer to execute the steps of: identifying a block that satisfies the specific condition from the blocks as an embeddable block; and replacing the identified block with a component of the acquired watermark information. A computer-readable recording medium that has been recorded. 9. A computer-readable recording medium on which a program for causing a computer to execute restoration of watermark information embedded in image data is recorded, wherein at least one bit plane of all bit planes expressing the image data is recorded. Sequentially blocking the bit data by n bits, identifying a block satisfying a specific condition from the blocks as an embedded block, and extracting n-bit data in the identified block as a component of watermark information And a computer-readable recording medium recording a program for causing a computer to execute the steps.