CN101604440A - Treatment method for reversibly watermarking vector map based on space characteristics - Google Patents

Abstract

The present invention is to provide a kind of treatment method for reversibly watermarking vector map based on space characteristics.According to Douglas-Pu Kefa the map vector element is carried out feature point extraction; Generate a random number sequence b according to seed key _i, this sequence is that a maximal value is no more than S _MaxRandom number sequence, this sequence will be as the offset sequence of unique point angle; The unique point that every polygon curve extracts is carried out nonlinear encryption; Watermark information is carried out the operation of Arnold scramble, and the watermark sequence behind the note process Arnold scramble is ω _j, ω _j∈ 0,1}; Reversible water mark embeds; Watermark extracting and former coordinate data are recovered; After extracting watermark, and on the harmless basis of recovering of carrier unique point coordinate, the map vector that contains linear encryption is carried out non-linear harmless recovery.Experimental result shows that this watermarking project strictness is reversible, has disguise preferably, is a kind of safety encipher that is used for secret map vector, the practical algorithm that follow the tracks of in the source.

Description

Treatment method for reversibly watermarking vector map based on space characteristics

(1) technical field

The present invention relates to geography information science, information security, reversible water mark, specifically is a kind of treatment method for reversibly watermarking vector map based on spatial character.

(2) background technology

The digital vector map is the core data that constitutes Geographic Information System (GIS), and it has many premium properties such as precision height, support high-quality convergent-divergent.The development of GIS technology makes map vector all have application prospects in a lot of fields, occupies crucial status in national economy, national defense construction, and its security relates to national security, scientific and technical cooperation and intellecture property etc.Therefore map vector is the same with other Digital Medias, is faced with a series of data security problems, comprises copyright protection, source tracking, distorts discriminating.

Digital watermark technology is the cutting edge technology of the protected data safety that grows up along with digitized process; it is under the prerequisite that does not influence former availability of data; secret information-watermark is combined with former data and hide wherein, become an inseparable part, come authentication data entitlement thus.The reversible water mark technology is called lossless data hiding again, be meant can complete recovery initial carrier data watermarking algorithm.Because the applied environment of map vector is relatively stricter, any change to original map data is avoided in hope usually, and the reversible water mark technology finally can be recovered the map vector of embed watermark intactly, and therefore reversible scheme is best solution.

At present the reversible water mark Study on Technology mainly concentrates on the grating image field, main method comprise utilize that invertible module adds, lossless compress, change histogram and difference enlarge the reversibility of coming implementation algorithm.Can be divided into two classes according to concrete implementation: spatial domain method and transform domain method.Data-hiding method based on the spatial domain has: 1, the method for Fridrich, this method is divided into original image the piece that is made of adjacent image point that does not overlap mutually earlier, set a discriminant function smoothness of piece is set, define a reversible transformation lowest order of pixel is reversed.2, the G-LSB method of Celik, at first each point data in the image is quantized, gray-scale value with each point in the image deducts this quantized value then, thereby obtain surplus, surplus is compressed, then it is become one group of new data stream with the information merging that needs to embed and be embedded in the image each point data-measuring value.3, the method for Ni van Leest, the document propose a kind of elder generation to image block, introduce a compression function then and act on histogram, make the existing room of histogram peak branch to be 0 if embed the value of data, then keep the gray value data of this point constant; If the value of the data that embed is 1, then the gray-scale value that will put becomes the room.4, the method for zhicheng, at first find out the peak point that occurs in the histogram in the image, find non-existent gray-scale value in the image then, all gray-scale values are not the points of histogram peak in the image by increasing or reducing again, make the existing room of peak value branch in the histogram, utilizing then in the image is that the each point of peak value embeds data.Image lossless data-hiding method based on domain of variation has: 1, the method for Xuan Guorong, a kind of method based on the integer wavelet transformation territory is proposed, earlier image is carried out the histogram adjustment and surpass scope in the original image, the reversible water mark algorithm that on frequency coefficient, carries out the watermark embedding then to avoid embedding because of information.2, the method for Jun Tian, this method are carried out lossless data hiding in conjunction with compress technique on the basis of the each point in the image being carried out the integer Haar wavelet wavelet transformation.3, the method for Yang Bian is to utilize integer DCT coefficient to distribute to be similar to the characteristics that Laplacian distributes, and the method realization image reversible water mark algorithm in conjunction with the bit displacement put forward in the SPIE information security branch in 2004.The reversibly watermarking vector map algorithm research is then at the early-stage.Michael Voigt proposed a kind of two-dimensional vector data reversible water mark algorithm based on discrete cosine transform in 2004: .2007 Shao Cheng forever for " Reversible Watermarking of2D-Vector Data " (Proceedings of the 2004multimedia and security workshop onMultimedia and security), the thought that people such as Wang Xiaotong enlarge based on difference, proposition is applied to the lossless data hiding algorithm of map vector: " Reversible Data-Hiding Scheme for 2-DVector Maps Based on Difference Expansion " (IEEE Transactions on informationforensics and security); " the lossless data hiding algorithm research of map vector " (Chinese image graphics journal).This is only three pieces of articles about vector map lossless data hiding of seeing at present.But also there is deficiency in the research of vector map lossless data hiding at present at the consideration of map vector own characteristic, the robustness of watermarking algorithm and the aspects such as data precision that watermark embeds the back map vector.

(3) summary of the invention

The object of the present invention is to provide a kind of can can't harm to recover original vector data, strict reversible, have concealed preferably treatment method for reversibly watermarking vector map based on space characteristics.

The object of the present invention is achieved like this:

Comprise the steps:

(1) according to Douglas-Pu Kefa (reduced parameter thresholding D is between 0m～1m) map vector element (polygon curve, polygon) is carried out feature point extraction;

(2) generate a random number sequence b according to seed key _i, this sequence is that a maximal value is no more than S _MaxRandom number sequence, this sequence will be as the offset sequence of unique point angle;

(3) unique point that every polygon curve is extracted is carried out nonlinear encryption;

(4) watermark information is carried out the operation of Arnold scramble, the watermark sequence behind the note process Arnold scramble is ω _j, ω _j∈ 0,1};

(5) reversible water mark embeds;

(6) watermark extracting and former coordinate data are recovered;

(7) after the extraction watermark, and on the harmless basis of recovering of carrier unique point coordinate, the map vector that contains linear encryption is carried out non-linear harmless recovery.

The present invention can also comprise:

1, the described unique point that every polygon curve the is extracted method of carrying out nonlinear encryption is:

At first carry out the selection of reference position line: in unique point angle migration processing process, moving-wire is not as the reference position line to select one, and all the other each unique points and starting point line are that angular deflection is carried out at the center with the starting point;

Secondly primitive character point angle is traveled through: every polygon curve in the map vector or polygon, with the reference position line is benchmark, with both sides to the left and right, travel through angle between the line line successively respectively, drawing one is the angle sequence θ of benchmark with the reference position line _i

At last to the unique point angle theta _iCarry out non-linear skew and come the encryption vectors map datum, corresponding deviation angle is random series d _i, the linear deflection formula is:

$\left\{\begin{array}{c}{{\mathrm{\&theta;}}_i}^{\&prime;}={\mathrm{\&theta;}}_i+d_i,i=\mathrm{1,2},...\mathrm{<figure-callout\; id="0"\; label="M"\; filenames="A2009100718790015H1.png"\; state="\{\{state\}\}">M</figure-callout>}\\ 0\&le;d_i\&le;S_{\max }\end{array}\right.$

Wherein M represents the number of all unique point angles of this map vector element (polygon curve and polygon), d _iThe random series that expression is generated by seed, θ _iAnd θ _i' represent the unique point angle after primitive character point angle and the linear deflection respectively.

2, the method for described reversible water mark embedding is:

The fraction part of the unique point coordinate of the map vector of handling with linear deflection is the embedding that carrier data is carried out watermark information; The original offset characteristic point sequence is designated as:

V _if＝{(x ₁，y ₁)，(x ₂，y ₂)，..，(x _n，y _n)}＝{x _f，y _f)|f＝1，2，...，n}

i＝1，...，m

V _IfRepresent the set of i bar polygon curve or polygonal carrier unique point, wherein (x _f, y _f) representing that respectively the horizontal ordinate of f carrier unique point in the i bar polygon curve, m represent polygon curve or the polygonal sum that extracts, n represents total number of the carrier unique point of i bar polygon curve;

Every polygon curve or polygon carrier unique point are extracted the fraction part of horizontal ordinate sequence respectively, and (radix point moves to right, and enlarges identical multiple and becomes integer) is designated as:

ZV _if′＝{(Zx ₁，Zy ₁)，(Zx ₂，Zy ₂)，..，(Zx _n，Zy _n)}＝{(Zx _f，Zy _f)|f＝1，2...，n}

i＝1，...，m

Ordinate Zy _fWith horizontal ordinate Zx _fWatermark embedding method identical; Horizontal ordinate Zx _fWatermark embedding method be:

Zx wherein _f' be intermediate variable, Be Zx _fAverage,

$\left\{\begin{array}{c}{{\mathrm{Zx}}_f}^{\&prime;}=(n+1){\mathrm{Zx}}_f-n\stackrel{\&OverBar;}{{\mathrm{Zx}}_f}\\ \stackrel{\&OverBar;}{{\mathrm{Zx}}_f}=\frac{\underset{f=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{Zx}}_f}{n}\\ f=\mathrm{1,2},...,n\end{array}\right.$

To the watermark sequence ω behind the process Arnold scramble _jCarry out the embedding of watermark sequence, formula is as follows:

Zx wherein _f", Zy _f" represent that respectively watermark embeds the fraction part round values of the horizontal ordinate in back, every polygon curve in the map vector is carried out this step repeatedly, finish the embedding of watermark, and carry out radix point and move to left, dwindle identical multiple, obtain to contain the unique point coordinate of watermark.

3, the method for watermark extracting and former coordinate data recovery is:

To every polygon curve or polygon feature point extraction, after the offsets point sequence extracts, to the fraction part ZV of the unique point coordinate sequence that contains watermark _If" be designated as:

ZV _if″＝{(Zx _f″，Zu _f″)|f＝1，2，...,n}

i＝0，1，...，m-1

Watermark information ω _jExtracting and can't harm restoration methods is

ω _j＝LSB(Zx _f″，Zy _f″)

f＝1，2，...，n

Original coordinates fraction part data value horizontal ordinate Zx _fHarmless reverting to:

Zx wherein _f ^*Expression is with Zx _f" value after the extreme lower position 0, ordinate Zy _fRecovery identical with it; Every polygon curve in the map vector is carried out this step repeatedly, finish the extraction of watermark; The fraction part Zx of unique point coordinate sequence _f, Zy _fAfter harmless the recovery, and carry out radix point and move to left, dwindle identical multiple, obtain the primitive characteristics point coordinate.

4, the described method that the map vector that contains linear encryption is carried out non-linear harmless recovery is:

1. in certain threshold value D scope (reduced parameter thresholding D is between 0m～1m) carries out Douglas-Pu Kefa to the map vector after the extraction watermark and carries out feature point extraction;

2. map vector polygon curve or polygonal unique point are carried out the selection of reference position line;

3. map vector unique point angle is traveled through;

4. the non-linear angle of unique point is recovered; On the basis that the unique point coordinate data is recovered,, obtain maximal value and be no more than S according to given seed key Seed _MaxRandom number sequence d _i, then original angle theta _iRecover according to following formula:

θ _i＝{θ _i′-d _i|d _i∈{0，1，...，S _max}}

i＝1，2，...，m

The present invention proposes a kind of reversibly watermarking vector map algorithm based on space characteristics.This algorithm one side is at " safety " problem of map vector, under the prerequisite that does not change map vector unique point relative position, according to of the harm of the non-linear scramble characteristic point position of key information to avoid unauthorized user that the illegal use of secret map vector is brought to national security; On the other hand, problem at map vector " high precision ", propose a kind of reversible water mark scheme, watermark information is embedded in the unique point behind the non-linear scramble reconditely, and when extracting watermark information, recover original vector data in conjunction with the scramble key is harmless.The advantage of this scheme is embodied in following three aspects:

(1) when authorized user uses the map vector that this algorithm process crosses, at first extracts watermark information, recover original vector data in conjunction with the scramble key is harmless.And withdraw from when using, watermark information embeds wherein automatically, makes map vector be in confidential state.

(2) when unauthorized user uses the map vector that this algorithm process crosses, because the processing to map vector has unpredictability, make and do not know that the user of key is difficult to crack, the use of map vector can not bring harm to national security under the state at this moment, and can determine the person liable that divulges a secret by the confidential information of hiding after piracy tracking is returned.

(3) the present invention adopts classical Douglas-Pu Kefa (Douglas-Peucker) to extract the carrier data of the unique point of map vector element as watermark, make this watermarking algorithm have good disguise, can when keeping the map shape facility, have anti-graph reduction ability as far as possible.

Reversibly watermarking vector map algorithm based on space characteristics of the present invention, on the one hand this algorithm is under the prerequisite that does not change map vector unique point relative position, the safety problem of bringing to country with the use of avoiding unauthorized user according to given its positional information of the non-linear scramble of key; Embed watermark information in the unique point of this algorithm behind scramble on the other hand, and when extracting watermark information, can can't harm in conjunction with the scramble key and recover original vector data.Experimental result shows that this watermarking project strictness is reversible, has disguise preferably, is a kind of safety encipher that is used for secret map vector, the practical algorithm that follow the tracks of in the source.

(4) description of drawings

Fig. 1 is the reversibly watermarking vector map scheme synoptic diagram based on space characteristics;

Fig. 2 (a)-Fig. 2 (d) is Douglas-Pu Kefa feature point extraction synoptic diagram;

Fig. 3 (1)-Fig. 3 (2) is a synoptic diagram before and after the non-linear skew of unique point, wherein before Fig. 3 (1) linear deflection, before Fig. 3 (2) linear deflection;

Fig. 4 (a)-Fig. 4 (d) is Chinese highway map vector and Harbin water anchor line (string) map vector embed watermark front and back synoptic diagram respectively, and wherein Fig. 4 (a), Fig. 4 (c) are respectively original map vector, and Fig. 4 (b), Fig. 4 (d) are respectively the map vector that contains watermark;

Fig. 5 (1)-Fig. 5 (4) is the watermark comparison diagram of former watermark and extraction, wherein Fig. 5 (1), Fig. 5 (2) are respectively the original watermark picture that embeds Chinese highway figure and Harbin water anchor line (string) figure, and Fig. 5 (3), Fig. 5 (4) are respectively the corresponding watermark picture that extracts;

Fig. 6 (a)-Fig. 6 (b) is respectively Chinese highway map vector and the Harbin water anchor line (string) map vector that recovers after the watermark extracting.

(5) embodiment

For example the present invention is done description in more detail below in conjunction with accompanying drawing:

As shown in Figure 1, the present invention is based on the reversibly watermarking vector map scheme synoptic diagram of space characteristics, this method totally is divided into three aspects: A, the non-linear migration processing of map vector unique point; B, vector map watermark embed and reversible recovery; C, the non-linear recovery of map vector unique point.

A, the non-linear migration processing of map vector unique point, step is as follows:

(1) according to Douglas-Pu Kefa (reduced parameter thresholding D is between 0m～1m) map vector element (polygon curve, polygon) is carried out feature point extraction;

In order to make the vector map watermark algorithm have anti-graph reduction ability, the present invention from the polygon curve of map vector and polygon formal element extract minutiae as the carrier data of watermark information.Unique point promptly is to keep the point of polygon curve or polygon curve shape facility.The feature point extraction algorithm is taked classical Douglas-Pu Kefa.Be a polygon curve feature point extraction synoptic diagram as shown in Figure 2.The set of all apex coordinates is designated as V and is designated as in this curve:

V＝{(x ₀，y ₀)，(x ₁，y ₁)，(x ₂，y ₂)，(x ₃，y ₃)，(x ₄，y ₄)，(x ₅，y ₅)，(x ₆，y ₆)}

Then under certain reduced parameter thresholding D (between 0m～1m), Douglas-Pu Kefa is reduced to unique point set V with this polygon curve after through (a)-(d) four steps as shown in Figure 2 _fFor:

V _f＝{(x ₀，y ₀)，(x ₁，y ₁)，(x ₂，y ₂)，(x ₃，y ₃)，(x ₆，y ₆)}

(2) generate a random number sequence b according to seed key _i. can accurately extract the primitive character point for guaranteeing the map vector after the skew in the recovery stage.Go out the offset threshold T of angle according to Douglas reduced parameter D correspondence, this just requires the maximal value S of the random number that generated _MaxMust satisfy:

S _max≤T

The random number generation function that the present invention adopts can be expressed as:

$\left\{\begin{array}{c}\mathrm{srand}\left(\mathrm{seed}\right)\\ d_i=\mathrm{rand}\left(\right)\%S_{\max }\end{array}\right.$

Wherein srand () function provides seed for rand () function, and Seed represents given seed key, d _iExpression generates a maximal value according to seed seed and is no more than S _MaxRandom number sequence, this sequence will be as the offset sequence of unique point angle.

(3) unique point that every polygon curve is extracted is carried out nonlinear encryption;

At first carry out the selection of reference position line: in unique point angle migration processing process, moving-wire is not as the reference position line to select one, and all the other each unique points and starting point line are that angular deflection is carried out at the center with the starting point.The reference position line promptly is to be that starting point is the straight line of terminal point with the intermediate point with the initial characteristics point.The polygon curve that N unique point for example arranged, then Individual unique point is an intermediate point.。

Secondly primitive character point angle is traveled through: to every polygon curve in the map vector or polygon, be benchmark, with both sides to the left and right, travel through angle between the line line successively respectively with the reference position line.As shown in Figure 3, the reference position line is line (x ₀, y ₀(the x of)-＞ ₂, y ₂), travel through the original offset angle successively, line (x ₀, y ₀(the x of)-＞ ₂, y ₂) and left side bearing (x ₀, y ₀(the x of)-＞ ₃, y ₃) angle theta ₁, line (x ₀, y ₀(the x of)-＞ ₃, y ₃) and line (x ₀, y ₀(the x of)-＞ ₁, y ₁) angle theta ₂, reference position line (x ₀, y ₀(the x of)-＞ ₂, y ₂) and its right side bearing (x ₀, y ₀(the x of)-＞ ₆, y ₆) angle theta ₃Method travels through every the polygon curve or the polygon of map vector successively, and drawing one is the angle sequence θ of benchmark with the reference position line _i

At last to the unique point angle theta _iCarry out non-linear skew and come the encryption vectors map datum, corresponding deviation angle is random series d _i, the linear deflection formula is designated as:

$\left\{\begin{array}{c}{{\mathrm{\&theta;}}_i}^{\&prime;}={\mathrm{\&theta;}}_i+d_i,i=\mathrm{1,2},...\mathrm{<figure-callout\; id="0"\; label="M"\; filenames="A2009100718790015H1.png"\; state="\{\{state\}\}">M</figure-callout>}\\ 0\&le;d_i\&le;S_{\max }\end{array}\right.$

Wherein M represents the number of all unique point angles of this map vector element (polygon curve and polygon), d _iThe random series that expression is generated by seed.θ _iAnd θ _i' represent the unique point angle after primitive character point angle and the linear deflection respectively.

B, vector map watermark embed and reversible recovery, and step is as follows:

(4) in order to strengthen the security of watermark information, watermark information is carried out the operation of Arnold scramble, the watermark sequence behind the note process Arnold scramble is ω _j, ω _j∈ 0,1};

(5) reversible water mark embeds: in reversible water mark embeds, requirement realizes accurately reconstruct raw data, the fraction part (radix point moves to right, and enlarges identical multiple and becomes integer) of the unique point coordinate of the map vector that the present invention handled with linear deflection is carried out the embedding of watermark information for carrier data.Offsets point sequence (promptly removing the characteristic point sequence outside two unique points in the line of reference position) is designated as:

V _if＝{(x ₁，y ₁)，(x ₂，y ₂)，..，(x _n，y _n)}＝{x _f，y _f)|f＝1，2，...，n}

i＝1，...，m

V _IfRepresent the set of i bar polygon curve or polygonal carrier unique point.(x wherein _f, y _f) representing that respectively the horizontal ordinate of f carrier unique point in the i bar polygon curve, m represent the sum of the polygon curve (polygon) that extracts, n represents total number of the carrier unique point on the i bar polygon curve.

Every polygon curve or polygon carrier unique point are extracted the fraction part of horizontal ordinate sequence respectively, and (radix point moves to right, and enlarges identical multiple and becomes integer) is designated as:

ZV _if′＝{(Zx ₁，Zy ₁)，(Zx ₂，Zy ₂)，..，(Zx _n，Zy _n)}＝{(Zx _f，Zy _f)|f＝1，...，n}

i＝1，...，m

Horizontal ordinate Zx _fFor example is set forth watermark embedding method, ordinate Zy _fIdentical with it, Zx wherein _f' be intermediate variable, Be Zx _fAverage.

$\left\{\begin{array}{c}{{\mathrm{Zx}}_f}^{\&prime;}=(n+1){\mathrm{Zx}}_f-n\stackrel{\&OverBar;}{{\mathrm{Zx}}_f}\\ \stackrel{\&OverBar;}{{\mathrm{Zx}}_f}=\frac{\underset{f=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{Zx}}_f}{n}\\ f=\mathrm{1,2},...,n\end{array}\right.$

To the watermark sequence ω behind the process Arnold scramble _jCarry out the embedding of watermark sequence.Formula is as follows:

Zx wherein _f", Zy _f" represent that respectively watermark embeds the fraction part integer data value of the horizontal ordinate in back.Every polygon curve in the map vector is carried out this step repeatedly, finish the embedding of watermark.And carry out radix point and move to left, dwindle identical multiple, obtain to contain the unique point coordinate of watermark.As shown in Figure 4, be watermark embed before and after map vector contrast situation, wherein figure (a), (c) be original map vector, figure (b), (d) they are situation about embedding respectively behind (1) among Fig. 5, (2).

(6) watermark extracting and former coordinate data are recovered;

To every polygon curve or polygon feature point extraction, after the offsets point sequence extracts, to fraction part (radix point moves to right, and enlarges identical multiple and the becomes integer) ZV of the unique point coordinate sequence that contains watermark _If" be designated as:

ZV _if″＝{(Zx _f″，Zy _f″)|f＝1，2，...，n}

i＝0，1，...，m-1

Watermark information ω _jExtracting and can't harm restoration methods is

ω _j＝LSB(Zx _f″，Zy _f″)

f＝1，2，...，n

Original coordinates fraction part data value horizontal ordinate Zx _fHarmless recovery, ordinate Zy _fIdentical with it:

Zx wherein _f ^*Expression is with Zx _f" value after the extreme lower position 0.Every polygon curve in the map vector is carried out this step repeatedly, finish the extraction of watermark.The fraction part Zx of unique point coordinate sequence _f, Zy _fAfter harmless the recovery, and carry out radix point and move to left, dwindle identical multiple, obtain the primitive characteristics point coordinate.

C, the non-linear recovery of map vector unique point, step is as follows:

(7) after the extraction watermark, and on the harmless basis of recovering of carrier unique point coordinate, the map vector that contains linear encryption is carried out non-linear harmless recovery;

1. in simplifying threshold value D scope, the map vector after the extraction watermark is carried out Douglas-Pu Kefa carry out feature point extraction;

2. map vector polygon curve or polygonal unique point are carried out the selection of reference position line;

3. map vector unique point angle is traveled through;

5. the non-linear angle of unique point is recovered.On the basis that the unique point coordinate data is recovered,, obtain maximal value and be no more than S according to given seed key Seed _MaxRandom number sequence d _iThen original angle theta _iRecover according to following formula:

θ _i＝{θ _i′-d _i|d _i∈{0，1，...，S _max}}

i＝1，2，...，m

Figure among Fig. 5 (3) (4) is respectively the watermark information after the extraction, and the map vector after the recovery as shown in Figure 6.

Claims (5)

1, a kind of treatment method for reversibly watermarking vector map based on space characteristics is characterized in that comprising the steps:

(1) according to Douglas-Pu Kefa the map vector element is carried out feature point extraction;

(2) generate a random number sequence b according to seed key _i, this sequence is that a maximal value is no more than S _MaxRandom number sequence, this sequence will be as the offset sequence of unique point angle;

(3) unique point that every polygon curve is extracted is carried out nonlinear encryption;

(4) watermark information is carried out the operation of Arnold scramble, the watermark sequence behind the note process Arnold scramble is ω _j, ω _j∈ 0,1};

(5) reversible water mark embeds;

(6) watermark extracting and former coordinate data are recovered;

(7) after the extraction watermark, and on the harmless basis of recovering of carrier unique point coordinate, the map vector that contains linear encryption is carried out non-linear harmless recovery.

2, the treatment method for reversibly watermarking vector map based on space characteristics according to claim 1 is characterized in that the method that the described unique point that every polygon curve is extracted is carried out nonlinear encryption is:

At first carry out the selection of reference position line: in unique point angle migration processing process, moving-wire is not as the reference position line to select one, and all the other each unique points and starting point line are that angular deflection is carried out at the center with the starting point;

Secondly primitive character point angle is traveled through: every polygon curve in the map vector or polygon, with the reference position line is benchmark, with both sides to the left and right, travel through angle between the line line successively respectively, drawing one is the angle sequence θ of benchmark with the reference position line _i

At last to the unique point angle theta _iCarry out non-linear skew and come the encryption vectors map datum, corresponding deviation angle is random series d _i, the linear deflection formula is:

$\left\{\begin{array}{c}{{\mathrm{\&theta;}}_i}^{\&prime;}={\mathrm{\&theta;}}_i+d_i,i=\mathrm{1,2},...M\\ 0\&le;d_i\&le;S_{\max }\end{array}\right.$

Wherein M represents the number of all unique point angles of this map vector element, d _iThe random series that expression is generated by seed.θ _iAnd θ _i' represent the unique point angle after primitive character point angle and the linear deflection respectively.

3, the treatment method for reversibly watermarking vector map based on space characteristics according to claim 2 is characterized in that the method that described reversible water mark embeds is:

The fraction part of the unique point coordinate of the map vector of handling with linear deflection is the embedding that carrier data is carried out watermark information; The offsets point sequence is designated as:

V _if＝{(x ₁，y ₁)，(x ₂，y ₂)，..，(x _n，y _n)}＝{(x _f，y _f)|f＝1，2，...，n}

i＝1，...，m

V _IfRepresent the set of i bar polygon curve or polygonal carrier unique point, wherein (x _f, y _f) representing that respectively the horizontal ordinate of f carrier unique point in the i bar polygon curve, m represent polygon curve or the polygonal sum that extracts, n represents total number of the carrier unique point of i bar polygon curve;

Every polygon curve or polygon carrier unique point are extracted the fraction part of horizontal ordinate sequence respectively, are designated as:

ZV _if′＝{(Zx ₁，Zy ₁)，(Zx ₂，Zy ₂)，..，(Zx _n，Zy _n)}＝{(Zx _f，Zy _f)|f＝1，2，...，n}

i＝1，...，m

Ordinate Zy _fWith horizontal ordinate Zx _fWatermark embedding method identical; Horizontal ordinate Zx _fWatermark embedding method

For: Zx wherein _f' be intermediate variable, Be Zx _fAverage,

$\left\{\begin{array}{c}{{\mathrm{Zx}}_f}^{\&prime;}=(n+1){\mathrm{Zx}}_f-n\stackrel{\&OverBar;}{{\mathrm{Zx}}_f}\\ \stackrel{\&OverBar;}{{\mathrm{Zx}}_f}=\frac{\underset{f=1}{\overset{n}{\mathrm{\&Sigma;}}}{\mathrm{Zx}}_f}{n}\\ f=\mathrm{1,2},...,n\end{array}\right.$

To the watermark sequence ω behind the process Arnold scramble _jCarry out the embedding of watermark sequence, formula is as follows:

Zx wherein _f", Zy _f" represent that respectively watermark embeds the fraction part round values of the horizontal ordinate in back, every polygon curve in the map vector is carried out this step repeatedly, finish the embedding of watermark, and carry out radix point and move to left, dwindle identical multiple, obtain to contain the unique point coordinate of watermark.

4, the treatment method for reversibly watermarking vector map based on space characteristics according to claim 3 is characterized in that the method that watermark extracting and former coordinate data are recovered is:

To every polygon curve or polygon feature point extraction, after the offsets point sequence extracts, to the fraction part ZV of the unique point coordinate sequence that contains watermark _If" be designated as:

ZV _if″＝{(Zx _f″，Zy _f″)|f＝1，2，...，n}

i＝0，1，...，m-1

Watermark information ω _jExtracting and can't harm restoration methods is

ω _j＝LSB(Zx _f″，Zy _f″)

f＝1，2，...，n

Original coordinates fraction part data value horizontal ordinate Zx _fHarmless reverting to:

Zx wherein _f ^*Expression is with Zx _f" value after the extreme lower position 0, ordinate Zy _fRecovery identical with it; Every polygon curve in the map vector is carried out this step repeatedly, finish the extraction of watermark; The fraction part Zx of unique point coordinate sequence _f, Zy _fAfter harmless the recovery, and carry out radix point and move to left, dwindle identical multiple, obtain the primitive characteristics point coordinate.

5, the treatment method for reversibly watermarking vector map based on space characteristics according to claim 4 is characterized in that the described method that the map vector that contains linear encryption is carried out non-linear harmless recovery is:

1. according to Douglas-Pu Kefa (reduced parameter thresholding D is between 0m～1m), the map vector after the extraction watermark is carried out Douglas-Pu Kefa carry out feature point extraction;

2. map vector polygon curve or polygonal unique point are carried out the selection of reference position line;

3. map vector unique point angle is traveled through;

4. the non-linear angle of unique point is recovered; On the basis that the unique point coordinate data is recovered,, obtain maximal value and be no more than S according to given seed key Seed _MaxRandom number sequence d _i, then original angle theta _iRecover according to following formula:

θ _i＝{θ _i′-d _i|d _i∈{0，1，...，S _max}}。

i＝1，2，...，m

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