CN1648935A - Three dimension face identifying method based on polar spectrum image - Google Patents

Abstract

The 3D face identifying method based on polar spectrum image includes the following steps: 1) intercepting face characteristic area, which is one 3D spherical area with nose tip as center and proper radium; 2) mapping the intercepted 3D face area to 2D plane to obtain 2D face parameters: 3) expanding the 3D image of face and performing 2D image processing to obtain so-called polar spectrum image, which is planar image of face constructed from 3D image of face in different postures and is posture independent; and 4) identifying polar spectrum face image through proper algorithm. The present invention has the beneficial effect of identifying the face in different expressions.

Description

Three-dimensional face identification method based on polar spectrum image

Technical field

The present invention relates to a kind of three-dimensional face identification method, mainly is the three-dimensional face identification method based on polar spectrum image that a kind of new approaches based on parametrization and spectrum are handled three-dimensional face identification.

Background technology

Computer face identification has obtained many scientific payoffss up to now owing to its application prospects has obtained extensive studies.Under the variation owing to conditions such as shining in people's face portion expression, shooting angle or pickup light, the feature difference in the human face photo that obtains, therefore the recognition of face of two dimension is very restricted.

For overcome the face identification method that only depends on the two-dimension human face photo deficiency, we turn to three-dimensional face to sight.Along with the development of 3-D scanning technology, be present research focus based on the identity identifying method of three-dimensional face.Though three-dimensional face is comprising more information than plane picture, be not very ripe for the processing of three-dimensional face.On the one hand, for the different people's face of attitude, in alignment, need more computing time; On the other hand, because the scrambling in people's face space, the existing space statistical and analytical method also is difficult to be applied directly on the three-dimensional face.

Summary of the invention

The objective of the invention is to overcome above-mentioned deficiency and a kind of three-dimensional face identification method based on polar spectrum image be provided, mainly solve be different 3 d poses with expression under the recognition of face problem.

The technical solution adopted for the present invention to solve the technical problems.This three-dimensional face identification method based on polar spectrum image, 1), face characteristic zone intercepting its step is as follows:: with the nose is the center, choose suitable radius length and make a ball, utilize the space symmetrical feature of sphere that people's face is intercepted, the three-dimensional face curved surface area that just will be included in ball inside is as the face characteristic zone.2), the three-dimensional face zone that intercepts is mapped on the two-dimensional plane, the plane parameterization of three-dimensional face.3), three-dimensional face launched in the plane after, by the two dimensional image disposal route, the polar spectrum image of generation.At the people's face under the different attitudes, construct the irrelevant plane picture of a kind of attitude and be used for representing three-dimensional face, we claim that this image is a polar spectrum image.4), utilize algorithm to carry out people's face polar spectrum image identification, polar spectrum image can well adopt present two-dimentional recognizer to carry out recognition of face, experimental result shows that FisherFaces has desirable recognition effect for the polar spectrum image of people's face.

The effect that the present invention is useful is: mainly solve be different 3 d poses with expression under the recognition of face problem.

Description of drawings

Fig. 1 is the process flow diagram of three-dimensional face identification of the present invention;

Fig. 2 is the planar synoptic diagram of simple 3D grid of the present invention;

Fig. 3 is a sampling synoptic diagram of the present invention;

Fig. 4 is ROC curve of the present invention and CMC curve synoptic diagram.

Embodiment:

Below in conjunction with drawings and Examples the present invention is further described.

One, whole concept of the present invention:

Three-dimensional face has scrambling in space distribution, existing method for expressing can't well be described three-dimensional face.We mainly consider following three aspects: when being mapped to three-dimensional planar on the two dimensional surface, how to keep the minimum disappearance of identifying information of three-dimensional face; Two dimensional surface after the mapping is handled, how to be made it irrelevant with initial attitude; Use any two-dimension human face recognition methods to discern the attitude unrelated images.

Two, this three-dimensional face identification method of the present invention based on polar spectrum image, (as shown in Figure 1), its step was as follows:

1, face characteristic zone intercepting:

The data volume of whole people's face is very big, and we consider to remove the fewer point of some quantity of information that comprise, thereby reaches the compromise of information and data volume.Make discovery from observation, it is the part at center that the feature of people's face mainly is distributed in the nose.In this piece zone, comprised eyes, the principal character of people's faces such as face and nose, they play a part very crucial for recognition of face.Because the uncertainty of people's face direction when scanning is even also there is the otherness on the direction in same individual's scanning result.When making the space intercepting like this, need to consider that the intercepting result must guarantee the independence of direction in space.

Here propose with the nose is the center, the length of choosing radius is approximately nose and makes a ball to about the corners of the mouth, make and people's face surface intersection, utilize the space symmetrical feature of sphere that people's face is intercepted, the three-dimensional face curved surface area that just will be included in ball inside is as the face characteristic zone.Characteristic area comprises the eyes of people's face, principal characters such as nose and face.Because the spatial symmetry of spheroid, so no matter how people's face changes on the direction in space, as long as determined the centre of sphere, the intersecting area of ball and people's face curved surface is just constant forever.So just in the intercepting characteristic area, guaranteed the orientation independent of primitive man's face.

2, three-dimensional face is mapped on the two-dimensional plane, the plane parameterization of three-dimensional face;

Also there are not good a kind of analysis and disposal route for three-dimensional body at present, but very ripe for the processing of two dimensional image.Therefore three-dimensional face is mapped on the two-dimensional plane, analyze with the existing two-dimensional image processing method again, not only can significantly reduce the complexity of 3D processing, and can compare complicated pattern analysis and conversion to the people's face after the mapping, thereby obtain reasonable recognition result.When mapping, because the minimizing of dimension, the loss of information is inevitable, and therefore when mapping, needs to consider the loss minimum of identifying information.For the three-dimensional face grid, its main information can be summed up as two kinds of angle information and area information.We estimate information loss degree in people's face two dimensionization with the loss of these two kinds of information.In order better to say something, we at first consider the information loss of simple 3D grid in mapping as shown in Figure 2.The information loss of its angle and area can be calculated by equation (1) (2).

1) angle information loss:

$E_A=\underset{\mathrm{neighbour\; edges}(i,j)}{\mathrm{\Σ}}\cot {\mathrm{\α}}_{\mathrm{ij}}{|u_i-u_j|}^2---\left(1\right)$

2) area information loss:

$E_X=\underset{j\∈N\left(i\right)}{\mathrm{\Σ}}\frac{(\cot {\mathrm{\γ}}_{\mathrm{ij}}+\cot {\mathrm{\δ}}_{\mathrm{ij}})}{{|x_i-x_j|}^2}{(u_i-u_j)}^2---\left(2\right)$

The key issue of complanation is exactly that the quantity of information of the two-dimensional person's face that the obtains loss how to make is minimum.Here, we consider to work as E _AAnd E _XReach respectively hour, both of these case is to the result's of mapping influence.From Fig. 2 we as can be seen: under the fixing situation of frontier point, unique variable shines upon the central point u of plane U ' exactly _i, so E _AAnd E _XVariation be along with u _iAnd change.Work as E _AAnd E _XWhen getting minimum value, must have

$\frac{\∂E_A}{\∂u_i}=\underset{j\∈N\left(i\right)}{\mathrm{\Σ}}(\cot {\mathrm{\α}}_{\mathrm{ij}}+\cot {\mathrm{\β}}_{\mathrm{ij}})(u_i-u_j)=0---\left(3\right)$

$\frac{\∂E_X}{\∂u_i}=\underset{j\∈N\left(i\right)}{\mathrm{\Σ}}\frac{(\cot {\mathrm{\γ}}_{\mathrm{ij}}+\cot {\mathrm{\δ}}_{\mathrm{ij}})}{{|x_i-x_j|}^2}(u_i-u_j)=0---\left(4\right)$

Promote whole three-dimensional face, can obtain:

$M^A\left[\begin{array}{c}{U}_{\mathrm{inetrnal}}\\ U_{\mathrm{boundary}}\end{array}\right]=0$ $M_{\mathrm{ij}}^A=\left\{\begin{array}{cc}\cot \left({\mathrm{\α}}_{\mathrm{ij}}\right)+\cot \left({\mathrm{\β}}_{\mathrm{ij}}\right)& \mathrm{if\; j}\∈N\left(i\right)\\ -{\mathrm{\Σ}}_{k\∈N\left(i\right)}{M}_{\mathrm{ik}}^A& \mathrm{if\; i}=j\\ 0& \mathrm{Otherwise}\end{array}\right.---\left(5\right)$

$M^X\left[\begin{array}{c}{U}_{\mathrm{inetrnal}}\\ U_{\mathrm{boundary}}\end{array}\right]=0$ $M_{\mathrm{ij}}^X=\left\{\begin{array}{cc}(\cot \left({\mathrm{\γ}}_{\mathrm{ij}}\right)+\cot {\left(}_{\mathrm{\β}\mathrm{ij}})/{|x_i-x_j|}^2& \mathrm{if\; j}\∈N\left(i\right)\\ -{\mathrm{\Σ}}_{k\∈N\left(i\right)}{M}_{\mathrm{ik}}^X& \mathrm{if\; i}=j\\ 0& \mathrm{otherwise}\end{array}\right.---\left(6\right)$

Work as E _AOr E _XReach respectively hour, be mapped to the point set U on the plane _InetrnalAnd U _BoundaryNeed satisfy equation 5 or equation 6, wherein U _InetrnalAnd U _BoundaryInternal point set after the behaviour face two dimensionization and external point set.Equation 5 and 6 is difficult to satisfy simultaneously, therefore uses balance parameters α to be used for regulating E yet in fact, _AAnd E _XShared proportion is very necessary in the two dimension result.This just means that we can come adjusting angle information loss and area information loss according to the actual needs.Shown in equation 7:

$M\left[\begin{array}{c}{U}_{\mathrm{inetrnal}}\\ U_{\mathrm{boundary}}\end{array}\right]=\left[\begin{array}{c}0\\ U_{\mathrm{boundary}}\end{array}\right]=0M=\mathrm{\α}{M}^A+(1-\mathrm{\α})M^X---\left(7\right)$

Equation 7 is to be based upon on the fixing condition of frontier point, therefore, with the frontier point of original three-dimensional face, is distributed in radius and is on 600 the circle, is U _Boundary, separate the mapping that linear equation promptly obtains internal point.

3, three-dimensional face is launched in the plane after, by the two dimensional image disposal route, the polar spectrum image of generation;

For the same individual face on any direction, the circular mapping area that obtains according to said method exists different on the anglec of rotation.We have constructed the rotation problem that polar spectrum image comes process angle.Polar spectrum image has been realized the independence of angle rotation by the two-dimensional fourier transform under the polar coordinates.This just means that regardless of the inceptive direction of a three-dimensional face, his polar spectrum image is always identical.In the recognition of face at present, particularly identification based on expression, for the alignment between the different people face be all the time one not only consuming time but also consume the task of power.The orientation independent of polar spectrum image needs complicated calculating alignment, not only can accelerate the speed discerned greatly, and has avoided the error that produced by the alignment of people's face.The generation flow process of polar spectrum image is as follows:

1), polar coordinates change

People's face coordinate after the mapping is based upon Cartesian coordinates and fastens, but the two dimensional image that causes owing to the initialization direction of three-dimensional face can not show on Cartesian coordinates very intuitively in the difference on the anglec of rotation, therefore we at first the image transitions of two dimension to polar coordinate image, then new image can be expressed as g (ρ, θ).Under polar coordinates, after the center of circle rotates Δ σ, image rotating is g (ρ, θ+Δ σ), be that rotational transform under the Cartesian coordinates can realize with simple translation transformation under polar coordinates, owing in map image, only have the variation of rotation, therefore be transformed into the displacement that just only exists under the polar coordinates on the θ direction.

In the process of changes in coordinates, we must guarantee ρ and the consistance of θ in sampling.Promptly as shown in Figure 3: in the distance center of circle is the r/2 place, and the sampling interval at radian direction and radial direction that makes is roughly the same.Suppose polar image size for (K, L), thereby we obtain, $\frac{2\mathrm{\π}}{L}\×\frac{r}{2}=\frac{r}{K},$ Be L=π K ≈ 3K.Therefore the image length breadth ratio after resampling and the polar coordinatesization is 1: 3, and same individual's polar coordinate image only exists translation to change.

2), two-dimensional fourier transform

Initial three-dimensional face has only the difference of displacement on polar coordinate image, through after the two-dimentional fourier conversion, the different polar coordinate image of displacement produces identical polar spectrum image, so two-dimensional fourier transform is used to generate the spectrum of polar coordinate image, shown in equation 8:

$F(k,l)=\frac{1}{\mathrm{MN}}\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{N-1}{\mathrm{\&Sigma;}}}f(i,j)e^{-i2\mathrm{\&pi;}(\frac{\mathrm{ki}}{M}+\frac{\mathrm{lj}}{N})}--0<k<K,0<l<L---\left(8\right)$

Wherein (i is that polar coordinate image is in point (I, j) pairing value j) to f.Through after the two-dimentional fourier conversion, the different polar coordinate image of displacement produces identical polar spectrum image, and initial three-dimensional face has only the difference of displacement so polar spectrum image and the most initial orientation independent of three-dimensional face on polar coordinate image.

4, utilize the FisherFaces algorithm to carry out the identification of people's face polar spectrum image.

The FisherFaces algorithm is based upon on the Fisher sorting technique.The essence of sorter is exactly by linear or nonlinear conversion, and the ratio of the interior sample dispersion of sample and class reaches maximum between the class that makes, that is:

$W_{\mathrm{opt}}=\arg \underset{W}{\max }\frac{\left|W^T{S}_{B}W\right|}{\left|W^T{S}_{W}W\right|}$

S _B, S _WBe expressed as the dispersion of sample between the dispersion of sample in the class and class respectively:

$S_B=\underset{i=1}{\overset{c}{\mathrm{\&Sigma;}}}{N}_i({\mathrm{\&mu;}}_i-\mathrm{\&mu;}){({\mathrm{\&mu;}}_j-\mathrm{\&mu;})}^T$

$S_w=\underset{i=1}{\overset{c}{\mathrm{\&Sigma;}}}\underset{x_k\&Element;X_i}{\mathrm{\&Sigma;}}(x_k-{\mathrm{\&mu;}}_i){(x_k-{\mathrm{\&mu;}}_i)}^T$

Wherein, c is the classification number of sample, N ₁Be the number of i class sample, μ _iBe the mean value of i class sample, μ is the mean value of sample, x _kBe the value of single sample, X _iIt is the set of i class sample.This is the basic thought of sorter.

And in Fisherfaces, we use following formula to calculate W _Opt:

$W_{\mathrm{opt}}=W_{\mathrm{fld}}^T{W}_{\mathrm{pca}}^T$

W _PcaAnd W _FldBe defined as follows:

$W_{\mathrm{fld}}=\arg \underset{W}{\max }\frac{\left|W^T{W}_{\mathrm{pca}}^T{S}_B{W}_{\mathrm{pca}}W\right|}{\left|W^T{W}_{\mathrm{pca}}^T{S}_W{W}_{\mathrm{pca}}W\right|}$

$W_{\mathrm{pca}}=\arg \underset{W}{\max }\left|W^T{S}_{T}W\right|,$ $S_T=\underset{k=1}{\overset{N}{\mathrm{\&Sigma;}}}(x_k-\mathrm{\&mu;}{)(x_k-\mathrm{\&mu;})}^T$

S _TDispersion for whole sample.

W _OptBe the transformation matrix of linear space, sample is through W _OptLinear space change, the sample that makes projects in the linear space that dimension is c-1, and of a sort sample gets together as much as possible, inhomogeneous sample separates as much as possible, thereby reaches the purpose of classification.On polar spectrum image, use the FisherFaces algorithm, have good recognition effect.

Three, checking result:

In order to verify the effect of this algorithm to three-dimensional face identification, we verify this algorithm on the 3D_RMA face database.S1m and two parts of s2m of the 3D_RMA face database that we have used, every part has 30 people, everyone three people's faces.

We are the centre of sphere with the nose, with to the general corners of the mouth be radius apart from length, i.e. it is 600 that intercepting makes unified intercepting radius, obtains having been comprised eyes, major parts such as nose and face by the zone after intercepting.

During two-dimensional map, we set circle and are the border, the frontier point of three-dimensional face according to range distribution on circumference, obtain people's face mapping on the two dimension according to the tolerance of the above-mentioned minimum information loss of mentioning, and to make the adjusting parameter alpha between angle information loss and the area information loss be 0.5.

After two-dimension human face process polar coordinate transform and Fourier conversion, the polar spectrum image that obtains is that owing to the orientation independent of polar spectrum image for primitive man's face, we carry out the recognition of face of final step with its input as the FisherFaces algorithm.

Four, performance specification:

General common use EER and CMC show that the value of its recognition capability: EER is low more, illustrate that performance is good more; The CMC value is high more, illustrates that performance is good more.For the more efficient use data, we adopt the standard of leaving-one method to calculate the value of EER.Below two experiments prove the superiority of this system:

1) adopt leaving-one method that s1m and s2m are calculated final EER value, under the variation of sampling parameter K from 10 to 50, its result is as follows:

DatabaseK	10	?15	?20	?25	?30	?35	?40	?45	?50
										?S1M(％)	7.10	?6.67	?6.67	?6.67	?6.26	?5.96	?5.15	?3.33	?3.32
?S2M(％)	10.56	?9.44	?9.44	?9.76	?8.89	?8.89	?8.71	?9.15	?8.97

2) utilize the s2m storehouse to do training sample, s1m does test sample book in the storehouse, and the value of K is 50, and its ROC curve and CMC curve are as shown in Figure 4.

Five, experiment conclusion:

By experimental result as can be seen: adopt and image is done identification, on EER and two indexs of CMC, obtained more satisfactory result based on the Fisherfaces algorithm of auroral spectrum.The total system flow process has made full use of plane parameterization, thereby the attribute of polar coordinates and TWO-DIMENSIONAL FOURIER obtains the polar spectrum image that need not align.Thereby required a large amount of computing time when having avoided three-dimensional face alignment or two dimensional surface alignment.Every people's face in the 3D_RMA storehouse has only 3000 joints, and everyone face is not that the value of EER has reached 3.32% under the very accurate situation, this in the method for present three-dimensional face identification than higher.

Claims (8)

1, a kind of three-dimensional face identification method based on polar spectrum image, it is characterized in that, 1), face characteristic zone intercepting its step is as follows:: with the nose is the center, choose suitable radius length and make a ball, utilize the space symmetrical feature of sphere that people's face is intercepted, the three-dimensional face curved surface area that just will be included in ball inside is as the face characteristic zone; 2), the three-dimensional face zone that intercepts is mapped on the two-dimensional plane, the plane parameterization of three-dimensional face; 3), three-dimensional face launched in the plane after, by the two dimensional image disposal route, the polar spectrum image of generation; 4), utilize algorithm to carry out the identification of people's face polar spectrum image.

2, the three-dimensional face identification method based on polar spectrum image according to claim 1 is characterized in that: the radius described in the step 1) is the length of nose to the corners of the mouth.

3, the three-dimensional face identification method based on polar spectrum image according to claim 1, it is characterized in that: in step 2) in angle information and area information two basic tolerance as people's face information, when the planar of three-dimensional face, calculate the least disadvantage of angle information and area information, to reach the purpose that three-dimensional face information keeps, concrete formula is as follows:

$M^A\left[\begin{array}{c}{U}_{\mathrm{ineirnal}}\\ U_{\mathrm{boundary}}\end{array}\right]=0$ $M_{\mathrm{ij}}^A=\left\{\begin{array}{cc}\cot \left({\mathrm{\&alpha;}}_{\mathrm{ij}}\right)+\cot \left({\mathrm{\&beta;}}_{\mathrm{ij}}\right)& \mathrm{if\; j}\&Element;N\left(i\right)\\ -{\mathrm{\&Sigma;}}_{k\&Element;N\left(i\right)}{M}_{\mathrm{ik}}^A& \mathrm{if\; i}=j\\ 0& \mathrm{Otherwise}\end{array}\right.---\left(5\right)$

$M^X\left[\begin{array}{c}{U}_{\mathrm{inetrnal}}\\ U_{\mathrm{boundary}}\end{array}\right]=0$ $M_{\mathrm{ij}}^X=\left\{\begin{array}{cc}(\cot \left({\mathrm{\&gamma;}}_{\mathrm{ij}}\right)+\cot \left({\mathrm{\&beta;}}_{\mathrm{ij}}\right))/{|x_i-x_j|}^2& \mathrm{if\; j}\&Element;N\left(i\right)\\ -{\mathrm{\&Sigma;}}_{k\&Element;N\left(i\right)}{M}_{\mathrm{ik}}^X& \mathrm{if\; i}=j\\ 0& \mathrm{otherwise}\end{array}\right.---\left(6\right).$

4, the three-dimensional face identification method based on polar spectrum image according to claim 1, it is characterized in that: in step 3), the two-dimension human face that shines upon is adopted polar coordinate transform and two-dimension fourier transform successively, thereby obtain the polar spectrum image of irrelevant to rotation by the two dimensional image disposal route; Polar coordinates change be with the image transitions of two dimension to polar coordinate image, new image can be expressed as g (ρ, θ); Through generating the spectrum of polar coordinate image after the two-dimentional fourier conversion, the different polar coordinate image of displacement produces identical polar spectrum image, shown in equation 8:

$F(k,l)=\frac{1}{\mathrm{MN}}\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}\underset{j=0}{\overset{N-1}{\mathrm{\&Sigma;}}}f(i,j)e^{-i2\mathrm{\&pi;}(\frac{\mathrm{ki}}{M}+\frac{\mathrm{lj}}{N})},0<k<K,0<l<L---\left(8\right).$

5, the three-dimensional face identification method based on polar spectrum image according to claim 1, it is characterized in that: in step 4), adopt the FisherFaces algorithm that the training sample data are trained, according to training result with the test sample book dimensionality reduction, classification then makes between class that the ratio of sample dispersion reaches maximum in the sample and class.

6, the three-dimensional face identification method based on polar spectrum image according to claim 3 is characterized in that: introduces balance parameters α, loses ratio to come adjusting angle information loss and area information according to the actual needs, shown in formula:

$M\left[\begin{array}{c}{U}_{\mathrm{inetrnal}}\\ U_{\mathrm{boundary}}\end{array}\right]=\left[\begin{array}{c}0\\ U_{\mathrm{boundary}}\end{array}\right]=0,M=\mathrm{\&alpha;}{M}^A+(1-\mathrm{\&alpha;})M^X---\left(7\right).$

7, the three-dimensional face identification method based on polar spectrum image according to claim 3 is characterized in that: can preestablish frontier point or internal point after the mapping as required, to satisfy the requirement of mapping.

8, the three-dimensional face identification method based on polar spectrum image according to claim 4 is characterized in that: in polar conversion process, make at the sampling interval of radian direction and radial direction roughly the same, to guarantee ρ and the θ consistance in sampling.