CN101833746A - Method for embedding reversible watermark in digital image and method for extracting reversible watermark from digital image - Google Patents
Method for embedding reversible watermark in digital image and method for extracting reversible watermark from digital image Download PDFInfo
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Abstract
The invention relates to a method for embedding a reversible watermark in a digital image and a method for extracting the reversible watermark from the digital image, and belongs to the field of information technology. The method for embedding the reversible watermark comprises the following steps of: dividing a carrier image and establishing a location mark sequence LMC, and dividing all pixels into three parts of I1, I2, and I3; embedding watermark in the pixel blocks in the I1 and I3; recording the lowest effective bit in the I1 into a sequence C, and using the LMC to replace the lowest effective bit in the I1; and finally, embedding the sequence C into an embeddable pixel block in the I2. The method for extracting the reversible watermark comprises the following steps of: dividing the carrier image and extracting the location mark sequence LMC; then dividing the pixel blocks into three parts of I1, I2, and I3; performing reverse transformation on the pixel blocks in the I2 according to the LMC to obtain an original pixel value sequence C; replacing the lowest effective bit in the I1 by the value in the sequence C; and finally, performing reverse transformation on the pixel blocks in the I1 and I3 according to the LMC to acquire an original pixel value and embedded watermark information. The method for embedding the reversible watermark in the digital image and the method for extracting the reversible watermark from the digital image improve the embedding capacity and do not need the original images during extraction.
Description
Technical field
The invention belongs to Information hiding and digital watermark technology field, relate in particular to the embedding grammar and the extracting method thereof of reversible water mark in a kind of digital picture.
Background technology
Information hiding (Information Hiding) is a new research focus of information security field, the research of this direction more and more is subjected to people's attention in recent ten years, research troop enlarges rapidly, and its achievement in research has obtained using widely in fields such as military affairs, politics, commerce.It is differentiated for the authenticity of intellectual property protection, vital document and the digital signature of the data communication of carrying out concerning security matters under open network environment, digital product and the message source tracking of classified papers after divulging a secret provides reliable security assurance information.
Digital watermarking (Digital Watermarking) and image latent writing (Steganography) are two big branches of Information Hiding Techniques.There are a lot of something in common in this two big branch on technology realizes, but characteristics are respectively arranged, and its purpose is very different.The purpose of digital watermark technology is that multi-medium data is carried out copyright protection, thereby more lays particular emphasis on the robustness of secret information; And the purpose of image latent writing technology is for information is sent in confidence, safely, owing to not cause third-party suspection as much as possible, thereby more pay attention to send the disguise of message.
Digital watermarking is a kind of useful information to be embedded into process in the multimedia file.For most of watermarking algorithms, the redundant information of carrier signal can be extracted out and substitute with watermark.Thereby after watermark embedded, carrier signal will be destroyed, and recover fully the very difficult content behind embed watermark.Yet in medical science and more military application, carrier image is very important for graphical analysis.The protection of this class view data integrality can realize by embed watermark, but require can recover original image fully after the watermark extracting.Under this condition, the notion that can extract watermark and can recover the reversible water mark of original image is suggested, for this class problem provides a kind of better solution.
In general, the quality of evaluation reversible water mark method mainly is from two aspects: embedding rate and visual quality.Specifically, wish exactly on the basis that increases the embedding rate as far as possible, keep less degree of distortion.In order to reach this purpose, a series of method is suggested, as: based on the algorithm of histogram translation, based on the algorithm of compress technique, based on the algorithm of integer transform.These methods can reach goodr effect, also can satisfy the application requirements to reversible water mark substantially.
Yet, by above method discovered that the existing reversible water mark method that is used for all is difficult to satisfy simultaneously following requirement:
(1) high embedding rate.We embed the embedding rate size that rate (being the bit number that each pixel can embed) is weighed each class methods with unit.Unit embedding rate value is big more, and the embedding rate is high more, and the embedding ability of algorithm is strong more.By contrasting algorithm in the past, we find under the condition that once embeds, to have only several algorithms seldom can reach 1.0 unit embedding rate;
(2) low distortion.We weigh the degree of distortion of image behind the embed watermark with Y-PSNR.Y-PSNR is big more, and degree of distortion is low more.Existing reversible water mark method is under the smaller situation of embedding rate, and Y-PSNR is bigger.Yet along with the embedding rate is increasing, the decline that Y-PSNR can be by a relatively large margin causes the visual effect of watermarking images very bad.
(3) freely embed the data of any bit.In existing watermarking algorithm, having much is freely to select the embedding rate as required, and this has brought very big inconvenience with regard to the application of giving reversible water mark.
Summary of the invention
The embedding grammar and the extracting method thereof that the purpose of this invention is to provide reversible water mark in a kind of digital picture can guarantee higher embedding rate and better visual effect, and solve the problem of coming free embed watermark according to the embedding rate.
The invention provides the embedding grammar of reversible water mark in a kind of digital picture, this method may further comprise the steps:
A. carrier image is divided into mutually disjoint block of pixels, the number of pixels in each piece is identical;
B. whether define a tick lables sequence, being used for writing down each block of pixels after the division can embed watermark and do not cause overflow problem, if certain block of pixels can embed watermark, then its corresponding tick lables sequence bit is 1, otherwise is 0.The definition of overflowing here is, the span of supposing pixel value is 0～L (for a general gray level image often 0～255), if after embedding, some pixel value then claims this result to overflow less than 0 or greater than L;
C. use compression algorithm that the tick lables sequence that obtains is carried out lossless compress, and on the tick lables sequence after the compression, add a unique ending flag sequence;
D. according to the length of the tick lables sequence after the compression, all block of pixels are divided into I
1, I
2, I
3Three parts;
E. to I
1And I
3In the block of pixels that can not cause overflow problem carry out specific integer transform, embed watermark information;
F. I
1The least significant bit (LSB) of each pixel value in the block of pixels is recorded in the sequence C, then they is replaced with the tick lables sequence after compressing.Here the definition of least significant bit (LSB) is: for a pixel value, represent it with binary form, last numerical value (0/1) is exactly its least significant bit (LSB).
G. use the mode identical that sequence C is embedded into I with embed watermark
2Block of pixels in.
The invention provides the extracting method of reversible water mark in a kind of digital picture, this method may further comprise the steps:
A. with the image behind the embed watermark, embed identical mode with described watermark and be divided into mutually disjoint block of pixels, the number of pixels in each piece is identical;
B. because in the telescopiny, the pixel value least significant bit (LSB) is extracted and is embedded into I in the sequence C
2Part, and the tick lables sequence is at I
1Part has become I
1Therefore the least significant bit (LSB) sequence that part is new reads the least significant bit (LSB) of each pixel value according to the raster scan order of image, up to unique ending flag sequence, the sequence that obtain this moment is exactly the tick lables sequence after the compression;
C. according to the length of the tick lables sequence after the compression, can be divided into I to block of pixels as the watermark embedding
1, I
2, I
3Three parts use compression algorithm that the tick lables sequence that obtains is decompressed then, the tick lables sequence before obtaining compressing;
D. the reference position flag sequence is to I
2In block of pixels carry out the inverse transformation of integer transform, and can obtain I thus
2The original pixel value of all pixels and embedding I
2In the least significant bit (LSB) sequence C;
E. come substitute I with the value in the sequence C
1The least significant bit (LSB) of middle pixel value;
F. the reference position flag sequence is to I
1And I
3Block of pixels is carried out the inverse transformation of integer transform, can obtain I thus
1And I
3The original pixel value of all pixels and embedding I
1And I
3In watermark information;
The invention provides a kind of flush mounting of realizing reversible water mark, this device comprises:
Divide module unit, be used for being divided into of digital picture of disjoint equal-sized block of pixels;
Identifying unit, but be used to judge which block of pixels is an embed watermark, obtain the tick lables sequence;
Compression unit is used for using compression algorithm to compress to the position flag sequence, the tick lables sequence after obtaining compressing, and a unique ending flag sequence is added at the end as a result after compression;
Embed the unit, be used to embed reversible water mark.At first block of pixels is divided into I according to the tick lables sequence after the compression
1, I
2, I
3Three parts, and a watermark that will embed converts the system form that is fit to embedding to.The zone bit information of reference position flag sequence then is to I
1And I
3Embeddable block of pixels is carried out the integer transform embed watermark information, and record embeds back I
1The least significant bit (LSB) sequence of middle pixel value.Again with the tick lables sequence substitute I after the compression
1In the least significant bit (LSB) sequence of pixel value, and in the mode identical with embed watermark the I that preserves
1The least significant bit (LSB) sequence be embedded into I
2In the embeddable block of pixels.
The invention provides a kind of extraction element of realizing reversible water mark, this device comprises:
Divide module unit, be used for being divided into of digital picture of disjoint equal-sized block of pixels;
Reading unit is used for the least significant bit (LSB) of read pixel value in order, up to unique ending flag sequence, thus the tick lables sequence after obtaining compressing;
Decompression unit is used for using compression algorithm to decompress to the tick lables sequence after the compression tick lables sequence before obtaining compressing;
Extraction unit is used to extract watermark and recovers original image.According to the tick lables sequence after the compression block of pixels is divided into I
1, I
2, I
3Three parts decompress to the position flag sequence with decompression unit, obtain the preceding tick lables sequence of compression, and the reference position flag sequence is to I
2In qualified block of pixels carry out specific integer transform inverse transformation to recover original image and to extract embedding information, convert it into binary mode in order to replace unit I
1The least significant bit (LSB) sequence of middle pixel value utilizes the tick lables sequence to I again
1And I
3In qualified block of pixels carry out specific integer transform inverse transformation recovering original image and to extract watermark, and recover this two-part original pixel value;
Adopt the present invention, can successfully realize embedding and the extraction of reversible water mark at gray level image, and the recovery of original image.The visual effect of the image behind the embed watermark is good, can reach very high unit embedding rate, and can freely embed the data of any embedding rate, does not need original image to participate in when watermark extracting and image recover in addition.Therefore, this method is a kind of well behaved reversible water mark algorithm, can be used for the Information hiding of medical treatment or military image and image recovery etc.
Compared with prior art, beneficial effect of the present invention is:
Adopt the present invention, successfully realizing embedding and the extraction of digital watermarking in gray level image, and the recovery of original image.The visual effect of the image behind the embed watermark is good, and higher embedding ability can be provided, and can embed watermark to sizing according to demand, does not need original image to participate in during watermark extracting.Therefore, this method is a kind of respond well reversible algorithm, can be used for Information hiding, the tracking of message source and the copyright protection etc. of important documents, has the wide range of commercial application prospect.
Description of drawings
Fig. 1 is a method flow diagram of the present invention;
(A) reversible water mark embedding grammar process flow diagram, (B) reversible water mark extracting method process flow diagram,
Fig. 2 is the gray level image of Lena;
(A) before the embed watermark information, (B) behind the embed watermark information,
Fig. 3 is the gray level image of Baboon;
(A) before the embed watermark information, (B) before the embed watermark information,
Fig. 4 is the gray level image of Airplane;
(A) before the embed watermark information, (B) before the embed watermark information.
Embodiment
In order to improve unit embedding rate, make the image of embed watermark keep good visual effect, accomplish that the blind extraction of watermark detection and image recover, the invention provides the extracting method of reversible water mark in the embedding grammar of reversible water mark in a kind of gray level image and a kind of gray level image.
Before introducing concrete embedding flow process, provide some basic definitions.At first, we provide the required integer transform T that uses of embed watermark information (X, W):
X=(x wherein
0, x
1... x
n) be the sets of pixel values of embed watermark block of pixels before, Y=(y
0, y
1... y
n) be embed watermark sets of pixel values afterwards, W=(w
1, w
1... w
n) (0≤w
i≤ k-1) be the watermark information that will embed, n 〉=1, k＞1 are two given integers.Here, we are with before and after the embed watermark, and the size of certain block of pixels distortion is calculated in the expectation of the quadratic sum of margin of image element, distortion size as can be known:
For a definite block of pixels, it is the quadratic function of variable with a (X) that d (X) is one, and desire makes it get minimum value (that is make distortion minimum), according to calculating when getting:
Can prove that the integer transform that we provide is an injection.Being inversely transformed into of it:
Wherein i ∈ 0,1 ... n}.This inverse transformation is used for extracting the watermark that embeds and recovering original pixel value in watermark extraction process.
But define the block of pixels of embed watermark below.Order:
A={X=(x
0, x
1..., x
n): x
iBe integer and 0≤x
i≤ 255}
A is the set of size for the possible pixel value group of institute of (n+1).In order to solve overflow problem, just implement integer transform after, for the pixel value that guarantees to obtain can not exceed the span (0～255) of gray level image pixel value, we define the subclass of an A:
D＝{X∈A：0≤kx
0-a(x)≤255，0≤kx
i-a(x)≤256-k(i＝1，...，n)}
According to definition as can be known, the element in the D set can guarantee T (X, W) ∈ A, that is avoided overflow problem.Yet in order to control the distortion after the embedding, but we are decided to be embedded block to the block of pixels that all pixel values are subordinated to D.But subclass: the S of definition D
t={ X ∈ D:e (X)≤t} is as the set that can embed the pixel value of block of pixels.T＞0th wherein, a given integer.
It is the embedding distortion that a block of pixels is estimated.
Some basic definitions that algorithm needs have been provided above.But embed and extract the operation of watermark, also have two problems not have to solve: one is four given parameter (n
1, n
2K, t) how to determine, the 2nd, also need these parameters in the time of because of extraction, between coding person and decoding person, transmitting how these parameter safeties? for first problem, at first we know, the effect of t mainly is that control embeds distortion, select as far as possible just to cause that embedding the little block of pixels of distortion comes embed watermark.At (n
1, n
2, k) under the given condition, t is more little, and it is more little then to embed the distortion meeting.On the other hand, t is more little, belongs to S
tThe pixel value group of set is just few more, but the block of pixels of embed watermark is also just few more, and unit embedding rate is also just low more.In order both to satisfy the requirement of embed watermark, can obtain little distortion again, as (n as far as possible
1, n
2, k) and the watermark that will embed size P (unit: bit) under the given condition, we need search for t, since 1 increase gradually, reach the upper limit of e (X) up to t
Perhaps but the size of embed watermark has surpassed till the P.Need to prove, can't satisfy the requirement that embeds the P bit if t has reached the upper limit of e (X), (n then is described at this
1, n
2, k) combination can not be satisfied the requirement that embeds the P bit watermark down.For (n
1, n
2, k), different parameters is selected all can be influential for the embedding ability and the distortion size of this method.In order to obtain embedding effect as well as possible, we set span a 2≤n
1, n
2≤ 5, { 2,4,8} is to (n for k ∈
1, n
2, k) enumerate, find to embed parameter given bit watermark and that the parameter distortion minimum is finally selected as us.For second problem of transmitting parameter, we can regard these parameters as supplementary, store these supplementarys with the space of certain-length, and it is added in tick lables sequence front after the compression, are embedded in the image therewith and are transmitted.This method can also be used to transmit all supplementarys that comprise the embedding rate.
The idiographic flow of the embedding grammar of reversible water mark is as follows, referring to Fig. 1 (A):
Step 101: obtain gray scale image;
Step 102: with image division is mutually disjoint n
1* n
2The block of pixels of size, each block of pixels comprises n+1 pixel, n+1=n
1* n
22≤n
1, n
2≤ 5,
Step 103:, judge that it whether can embed watermark, that is whether the pixel value group X of this block of pixels satisfies X ∈ S for each block of pixels
tIf, can, writing down one 1, otherwise write down one 0, we have just obtained the tick lables sequence LM of binary representation thus;
Step 104: with the mathematics coding LM is carried out lossless compress, and unique ending flag sequence of the interpolation of the tick lables sequence end after compression, obtaining sequence LMC thus, we suppose that the length of the LMC of sequence as a result of gained is L;
Step 105: all block of pixels are divided into three part: I
1, I
2, I
3, I wherein
1Comprise
Individual block of pixels, I
2Comprise
But the block of pixels of individual embed watermark, remaining is divided into I
3
Step 106: for I
1And I
3In each block of pixels, with reference to the record of compression front position flag sequence, if it is embeddable, that is the corresponding record of tick lables sequence is 1, then uses integer transform to carry out watermark and embeds, otherwise constant;
Step 107: record I
1In the least significant bit (LSB) of each pixel value, obtain the least significant bit (LSB) sequence C thus, and use the LMC substitute I
1The least significant bit (LSB) of middle pixel value.
Step 108: the method according to embed watermark is embedded into I to sequence C
2In embedded block of pixels in.
The idiographic flow of the extracting method of reversible water mark is as follows, referring to Fig. 1 (B):
Step 111: the gray level image that obtains the embed watermark signal;
Step 112:,, be divided into a plurality of block of pixels according to embedding identical mode with watermark with the gray level image of embed watermark signal;
Step 113: according to the least significant bit (LSB) of the raster scan order read pixel value of image, till meeting the ending flag sequence, tick lables sequence LMC after we can obtain to compress thus, then according to the length L of LMC, we can obtain like that to be similar to telescopiny
And then all block of pixels are divided into I
1, I
2, I
3In addition three parts, can also utilize digital coding that LMC is decompressed, the tick lables sequence LM before obtaining compressing;
Step 114: for I
2In each block of pixels, check the zone bit that it is corresponding in LM, if zone bit is 1, just separate with the inverse transformation of integer transform is counter, watermark that can obtain to embed and block of pixels original pixel value are if pixel value is 0, then do not carry out any operation, thus from I
2In can extract a sequence C, the least significant bit (LSB) sequence that it just defines in telescopiny;
Step 115: replace present I with C
1The least significant bit (LSB) of middle pixel value is for I
1And I
3In each block of pixels, separate according to the mode of similar step 114 is counter, can obtain to be embedded into I
1And I
3In watermark information and the original pixel value of their block of pixels, and then obtained original image and embed watermark.
We said the front that this method can realize freely embedding the watermark information to sizing, in order to reach this purpose, need make a bit little modification to top embedding extraction step.Suppose that we will embed the watermark of P bit, in telescopiny, in step 106, not to I
1And I
3But in the block of pixels of each embed watermark all embed, but after having embedded the P bit, just stop telescopiny, keep the residual pixel piece constant.Embedding big or small P can be embedded in the image according to above said supplementary transmission method.And when extracting, we can obtain supplementary P earlier.In step 115, only utilize the integer transform inverse transformation to extract I
1And I
3The middle P bit information that embeds keeps remaining block of pixels constant.Can realize freely embedding of watermark information thus.
The present invention is further illustrated below in conjunction with accompanying drawing:
One, watermark embed process:
1, given length is
Watermark signal W={w to be embedded
I, j, w wherein
I, j=0 or 1.Notice that watermark this moment is the binary representation form.When having determined that parameter k embeds, convert watermark to the k system.
2, set scope a 2≤n
1, n
2≤ 5, { 2,4,8} enumerates k ∈.We are for each group (n
1, n
2, k) possible value is selected corresponding suitable t value, that is allows t increase gradually from 1, is no less than P up to the embeddable watermark bit number of algorithm.Then for the (n of each group
1, n
2, k, t), operation 3-9 below carrying out.
3,512 * 512 the gray level image Lena that Fig. 2 (A) is provided is divided into mutually disjoint n
1* n
2The block of pixels of size, each block of pixels comprises (n+1) (n+1=n
1* n
2) individual pixel.
4,, judge its whether embed watermark, that is whether the pixel value group X of this block of pixels satisfies X ∈ S for each block of pixels
tIf, can, writing down one 1, otherwise write down one 0, we have just obtained the tick lables sequence LM of binary representation thus;
5, with the mathematics coding LM is carried out lossless compress, and unique ending flag sequence of the interpolation of the tick lables sequence end after compression, sequence LMC obtained thus; Write down n respectively with 33 bit numbers
1, n
2, k writes down t and P respectively with two 32 bit numbers, and these numbers all are added in LMC sequence front.We suppose that the total length of sequence as a result of gained is L.
6, all block of pixels are divided into three part: I
1, I
2, I
3, I wherein
1Comprise
Individual block of pixels, I
2Comprise
But the block of pixels of individual embed watermark, remaining is divided into I
3
7, for I
1And I
3In each block of pixels, with reference to the record of compression front position flag sequence, if it is embeddable, that is the corresponding record of tick lables sequence is 1, then uses integer transform to carry out watermark and embeds, otherwise constant; Till the whole embeddings of the watermark information of P bit finish.
8, record I
1In the least significant bit (LSB) of each pixel value, obtain the least significant bit (LSB) sequence C thus, and use the LMC substitute I
1The least significant bit (LSB) of middle pixel value.
9, according to the method for embed watermark, sequence C is embedded into I
2In embedded block of pixels in.Here notice that the C that we obtain is a binary sequence, embed, at first will become k system data sequence to it with integer transform.
10, for top every group of (n
1, n
2, k t), calculates the distortion size after embedding, and the image of selecting the distortion minimum is as the net result after embedding.
Two, watermark extraction process:
1, according to the watermarking images 2 (B) that obtains, the least significant bit (LSB) of order read pixel value till meeting the ending flag sequence, supposes that its length is L.Obtain supplementary n by preceding 73 that read
1, n
2, k, t and P, and then can be image division a plurality of block of pixels according to embedding identical mode with watermark; The supplementary back is the tick lables sequence LMC after the compression, can utilize digital coding that LMC is decompressed, the tick lables sequence LM before obtaining compressing.In addition, we can obtain like that to be similar to telescopiny
And then all block of pixels are divided into I
1, I
2, I
3Three parts;
2, for I
2In each block of pixels, check the zone bit that it is corresponding in LM, if zone bit is 1, just separate with the inverse transformation of integer transform is counter, data that can obtain to embed and block of pixels original pixel value if pixel value is 0, then do not carry out any operation.Notice that this moment, anti-data of separating the integer transform extraction were the k systems, change into 2 system forms to it, thus from I
2In can extract a sequence C, the least significant bit (LSB) sequence that it just defines in telescopiny.
3, replace present I with C
1The least significant bit (LSB) of middle pixel value is for I
1And I
3In each block of pixels, separate according to the mode of similar step 114 is counter, can progressively obtain to be embedded into I
1And I
3In watermark information and the original pixel value of their block of pixels, and then obtained original image and embed watermark.But be I
1And I
3In all embedded block of pixels all embedded watermark, so want reference parameter P when extracting,, then stop the anti-process of separating in case the watermark of extracting has equaled P, the maintenance block of pixels is constant.
4, above operation can obtain the watermark information W={w of original image 2 (A) and embedding
I, j.
By several embodiment the performance that embeds reversible water mark and extract water mark method in gray level image of the present invention is described again at last.
Embodiment one:
Width of cloth gray level image Baboon shown in Fig. 3 (A), we use method of the present invention that it is embedded
Bit watermark information.Flow process that watermark embeds and required parameter front are described in detail, no longer repeat here.Fig. 3 (B) is the image behind the embed watermark.Can see that the visual effect of the image behind the embed watermark is good, in fact, have only extremely simple parts of the more single texture of nose ambient color, could find out slightly that smoothness has a little difference, other local discoveries are difficult to find out the vestige that is modified.Then extract watermark, can successfully extract the watermark information of whole P bits, and recover original image by the watermarking algorithm among the present invention.
Above-mentioned example can reach good visual effect after can showing that this algorithm of use embeds.
Embodiment two:
Width of cloth gray level image Airplane to showing as Fig. 4 (A) embeds it with described method
Bit watermark information.The flow process that watermark embeds is identical with a last example with required parameter, no longer repeats here.Fig. 4 (B) is the image behind the embed watermark.Can therefrom successfully extract the watermark information of whole bits and can recover original image by the watermark extracting algorithm.
We have reached the unit picture element embedding rate of 1.8 bits in the above-mentioned example, and this is difficult getting in the reversible water mark algorithm.Illustrate that this method has higher embedding ability.
The invention provides a kind of device that embeds reversible water mark, this device comprises:
Divide module unit, be used for being divided into of digital picture of disjoint equal-sized block of pixels;
Identifying unit, but be used to judge which block of pixels is an embed watermark, obtain the tick lables sequence;
Compression unit is used for using compression algorithm to compress to the position flag sequence, and the tick lables sequence after obtaining compressing, and unique ending flag sequence of the interpolation of the end as a result after compression deposit various supplementarys in its beginning simultaneously;
Embed the unit, be used to embed reversible water mark.At first block of pixels is divided into I according to the tick lables sequence after the compression
1, I
2, I
3Three parts, and a watermark that will embed converts the system form that is fit to embedding to.The zone bit information of reference position flag sequence then is to I
1And I
3Embeddable block of pixels is carried out the integer transform embed watermark information, and I behind the record embed watermark
1The least significant bit (LSB) sequence of middle pixel value.With compression unit the position flag sequence is compressed again, the tick lables sequence substitute I after the compression
1In the least significant bit (LSB) sequence of pixel value, and in the mode identical with embed watermark the I that preserves
1The least significant bit (LSB) sequence be embedded into I
2In the embeddable block of pixels.
The embedding unit comprises: the system converting unit is used for scale-of-two watermark information that will embed or least significant bit (LSB) sequence are changed into the k system form that is fit to embedding; Judging unit judges according to the tick lables sequence of input whether a block of pixels can embed data; Grouped element is used for according to the length of tick lables sequence all block of pixels being divided into three group I
1, I
2, I
3Integer transform is implemented to one group of pixel value that can embed data in the integer transform unit; Replace and record cell, be used to write down I behind the embed watermark
1In the least significant bit (LSB) sequence of pixel value, and with the replacement of the tick lables sequence after compression least significant bit (LSB) sequence.
Below in conjunction with specific embodiment reversible water mark extraction of the present invention and recovery original image device are described:
The invention provides the device that a kind of reversible water mark extracts and recovers original image, this device comprises:
Divide module unit, be used for being divided into of digital picture of disjoint equal-sized block of pixels;
Reading unit is used for the least significant bit (LSB) of read pixel value in order, up to unique ending flag sequence, thus tick lables sequence after obtaining compressing and various supplementary;
Decompression unit is used for using compression algorithm to decompress to the tick lables sequence after the compression tick lables sequence before obtaining compressing;
Extraction unit is used to extract watermark and recovers original image.According to the tick lables sequence after the compression block of pixels is divided into I
1, I
2, I
3Three parts decompress to the position flag sequence with decompression unit, obtain the preceding tick lables sequence of compression, and the reference position flag sequence is to I
2In qualified block of pixels carry out specific integer transform inverse transformation to recover original image and to extract embedding information, convert it into binary mode in order to replace unit I
1The least significant bit (LSB) sequence of middle pixel value utilizes the tick lables sequence to I again
1And I
3In qualified block of pixels carry out specific integer transform inverse transformation recovering original image and to extract watermark, and recover this two-part original pixel value;
Extraction unit comprises: the system converting unit is used for k system watermark information or the least significant bit (LSB) sequence that will extract are changed into binary mode; Judging unit judges according to the tick lables sequence before the compression whether a block of pixels can embed data; Grouped element is used for according to the length of the tick lables sequence after the compression all block of pixels being divided into three group I
1, I
2, I
3The integer transform inverse transformation block is implemented the integer transform inverse transformation to the one group of pixel value that has embedded data; Replace the unit, with the tick lables sequence substitute I after the compression
1The least significant bit (LSB) sequence of pixel value.
Below in conjunction with specific embodiment the workflow of this watermark flush mounting is described (supposing that all parameters are given):
Step S01: the branch module unit with flush mounting is divided into mutually disjoint n with image 2 (A)
1* n
2The block of pixels of size, each block of pixels comprises (n+1) (n+1=n
1* n
2) individual pixel;
Step S02: judge with the identifying unit of flush mounting whether each block of pixels can embed data, we have just obtained the tick lables sequence LM of binary representation thus;
Step S03: the compression unit with flush mounting carries out lossless compress to LM, and a unique ending flag sequence is added at the tick lables sequence end after compression, add all supplementarys simultaneously in the starting position, obtain sequence LMC thus, we suppose that the length of the LMC of sequence as a result of gained is L;
Step S04: the embedding unit of using flush mounting is in watermark information and the LMC embedded images.Specifically with watermark embedding method step 105-108 partly.
Describe below in conjunction with the workflow of specific embodiment this watermark flush mounting:
Step S11: the reading unit of usefulness flush mounting is the least significant bit (LSB) of read pixel value in order, up to unique ending flag sequence, thus tick lables sequence LMC after obtaining compressing and various supplementary;
Step S12: the branch module unit with extraction element is divided into mutually disjoint n with image 2 (A)
1* n
2The block of pixels of size, each block of pixels comprises (n+1) (n+1=n
1* n
2) individual pixel;
Step S13: the decompression unit with extraction element decompresses the tick lables sequence LM before obtaining compressing to obtaining LMC.
Step S13: the extraction unit with extraction element extracts watermark information and recovers original image, the step 113-115 of concrete steps such as watermark extracting algorithm part.
Obviously, those skilled in the art can carry out various changes and modification to the present invention and not break away from the spirit and scope of the present invention.Like this, if of the present invention these are revised and modification belongs within the scope of claim of the present invention and equivalent technologies thereof, then the present invention also is intended to comprise these changes and modification interior.
Claims (11)
1. the embedding grammar of reversible water mark in the digital picture the steps include:
1) size of initialization or setting block of pixels is that n+1 pixel, integer transform are the integer transform of k system; Wherein n is that natural number, k are natural number;
2) the big young pathbreaker's carrier image according to block of pixels is divided into mutually disjoint several pixel blocks;
3) judge that each block of pixels whether can embed watermark, and judged result is kept in the tick lables sequence;
4) on the flag sequence of position, add an ending flag sequence;
5) according to 4) length L of the tick lables sequence of gained, all block of pixels are divided into I
1, I
2, I
3Three parts; I wherein
1Comprise
Individual block of pixels, I
2Comprise
The block of pixels of individual energy embed watermark, the residual pixel piece is divided into I
3In;
6) according to 3) the tick lables sequence that obtains, the integer transform that uses the k system is to I
1And I
3In each block of pixels carry out watermark and embed;
7) with I
1The least significant bit (LSB) of each pixel value is recorded in the sequence C in the contained block of pixels, and with 4) the tick lables sequence substitute I of gained
1The least significant bit (LSB) of middle pixel value;
8) use the integer transform of k system that sequence C is embedded into I
2In embedded block of pixels in.
2. the method for claim 1, the size that it is characterized in that described block of pixels is n
1* n
2Wherein, n
1* n
2=n+1, n
1, n
2Be respectively the length of side of block of pixels; Set n
1, n
2, k span, wherein, 2≤n
1≤ 5,2≤n
2≤ 5, k ∈ (2,4,8).
3. method as claimed in claim 2 is characterized in that described n
1, n
2, k obtaining value method be: enumerate n
1, n
2, k value, calculate certain the block of pixels degree of distortion behind the embed watermark respectively, choose degree of distortion n hour
1, n
2, k value.
4. the method for claim 1 is characterized in that in the described step 4), at first the tick lables sequence that obtains is carried out lossless compress, and adds an ending flag sequence on the tick lables sequence after the compression.
5. the method for claim 1 is characterized in that in the described step 3), judges that each block of pixels whether can embed watermark, and if could in this tick lables sequence the value of record respective pixel piece be 1, otherwise be 0; This tick lables sequence is binary tick lables sequence.
6. the extracting method of reversible water mark in the digital picture the steps include:
1) be mutually disjoint several pixel blocks with the image division behind the embed watermark; Big or small identical when wherein the size of block of pixels is with embed watermark, each block of pixels comprises n+1 pixel, and n is a natural number;
2) read the least significant bit (LSB) of each pixel value according to the scanning sequency of image, the ending flag sequence up to setting obtains a tick lables sequence;
3) according to 2) length L of the tick lables sequence of gained, all block of pixels are divided into I
1, I
2, I
3Three parts; I wherein
1Comprise
Individual block of pixels, I
2Comprise
The block of pixels of individual energy embed watermark, the residual pixel piece is divided into I
3In; K is the system number of integer transform, the value of k during with embed watermark value identical;
4) according to 2) the tick lables sequence of gained is to I
2In block of pixels carry out the inverse transformation of k system integer transform, obtain I
2The original pixel value of all pixels and embedding I
2In sequence C;
5) with the value substitute I in the sequence C
1The least significant bit (LSB) of middle pixel value;
6) according to 2) the tick lables sequence of gained is to I
1And I
3Block of pixels is carried out the inverse transformation of k system integer transform, obtains I
1And I
3The original pixel value of all pixels and be embedded into I
1And I
3In watermark information.
7. the embedding grammar of reversible water mark in the digital picture the steps include:
1) variable n is set
1, n
2, k and span thereof, the length of watermark signal to be embedded is the P bit, wherein, n
1, n
2Be respectively the length of side of block of pixels, k is the system of integer transform;
2) enumerate n
1, n
2, k value, for each group (n
1, n
2, k), set a degree of distortion threshold value t, if the degree of distortion that can embed the P bit watermark and embed block of pixels then writes down current group quaternary group information (n less than threshold value t
1, n
2, k, t);
3) according to each four-tuple (n
1, n
2, k t), is divided into mutually disjoint n with carrier image
1* n
2The block of pixels of size, each block of pixels comprises n+1 pixel;
4) judge that each block of pixels whether can embed watermark, and judged result is kept in the tick lables sequence;
5) with four-tuple (n
1, n
2, k t) in the record position flag sequence, and adds an ending flag sequence on the flag sequence of position;
6) according to 5) length L of the tick lables sequence of gained, all block of pixels are divided into I
1, I
2, I
3Three parts; I wherein
1Comprise
Individual block of pixels, I
2Comprise
The block of pixels of individual energy embed watermark, the residual pixel piece is divided into I
3In;
7) according to 4) the tick lables sequence that obtains, the integer transform that uses the k system is to I
1And I
3In block of pixels carry out watermark and embed, all embed up to P bit watermark information;
8) with I
1The least significant bit (LSB) of each pixel value is recorded in the sequence C in the contained block of pixels, and with 5) the tick lables sequence substitute I of gained
1The least significant bit (LSB) of middle pixel value;
9) use the integer transform of k system that sequence C is embedded into I
2In embedded block of pixels in;
10) calculate each four-tuple (n
1, n
2, k, t) corresponding image embeds degree of distortion, and the image of selecting the degree of distortion minimum is as embedded images.
8. method as claimed in claim 7 is characterized in that the n that sets
1, n
2, k span be respectively: 2≤n
1≤ 5,2≤n
2≤ 5, k ∈ (2,4,8).
9. method as claimed in claim 7 is characterized in that definite method of threshold value t is: according to current group of (n
1, n
2, when k) carrying out watermark and embed, threshold value t is increased gradually since 1, corresponding to each t value, if the degree of distortion of embedding block of pixels less than current t value, and can embed the P bit watermark, then getting current t value is current group of (n
1, n
2, embedding degree of distortion threshold value k).
10. as claim 7 or 8 or 9 described methods, it is characterized in that in the described step 5), at first the tick lables sequence that obtains is carried out lossless compress, and on the tick lables sequence after the compression, add an ending flag sequence.
11. the extracting method of reversible water mark the steps include: in the digital picture
1) read the least significant bit (LSB) of each pixel value according to the scanning sequency of image, the ending flag sequence up to setting obtains a tick lables sequence;
2) according to the four-tuple (n in the tick lables sequence
1, n
2, k is mutually disjoint block of pixels with image division t);
3) according to the length L of tick lables sequence, all block of pixels are divided into I
1, I
2, I
3Three parts; I wherein
1Comprise
Individual block of pixels, I
2Comprise
The block of pixels of individual energy embed watermark, the residual pixel piece is divided into I
3In; K is the system number of integer transform, the value of k during with embed watermark value identical;
4) according to the tick lables sequence to I
2In block of pixels carry out the inverse transformation of k system integer transform, obtain I
2The original pixel value of all pixels and embedding I
2In sequence C;
5) with the value substitute I in the sequence C
1The least significant bit (LSB) of middle pixel value;
6) according to the tick lables sequence to I
1And I
3Block of pixels is carried out the inverse transformation of k system integer transform, equals the P bit up to the watermark length of extracting, and obtains I
1And I
3The original pixel value of all pixels and be embedded into I
1And I
3In watermark information.
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