CN1169079C

CN1169079C - Computer Segmentation Method of TCM Tongue Image Based on Spline Snakes Model

Info

Publication number: CN1169079C
Application number: CNB021037973A
Authority: CN
Inventors: 沈兰荪; 卫保国
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2002-03-25
Filing date: 2002-03-25
Publication date: 2004-09-29
Anticipated expiration: 2022-03-25
Also published as: CN1367455A

Abstract

The present invention relates to a computer cutting method based on a sample strip Snakes model for a tongue picture of Chinese medicine. The present invention cuts a tongue body in the tongue picture of the Chinese medicine from the background to be convenient for the following characteristic analysis. The present invention adopts a digital camera to collect the tongue picture and input the picture to a computer to be processed, transmitted, etc. The method is characterized in that according to the statistical analysis of the shape of the tongue body, a mould plate of a tongue body contour which takes a rectangular region as an outer boundary is defined; with an analysis method of greyscale projection, a rectangular region is obtained to determine the approximate position and size of the tongue body; the present invention provides an initialization method for the tongue body contour, which is based on the greyscale projection and a rigid mould plate; prior knowledge relating to the tongue body contour is added into the energy function of a Snakes model; a Catmull-Rom sample strip Snakes model is used for representing the tongue body contour which is optimized by the greedy method; a tongue body contour is obtained from a colored tongue picture; a tongue body region is cut from the tongue body contour. The cutting method has accuracy and practicality.

Description

Traditional Chinese medical science tongue picture computing machine dividing method based on batten Snakes (Snakes) model

Technical field

The present invention relates to computing machine Medical image Processing field, designed a kind of tongue body dividing method, the tongue body in the traditional Chinese medical science tongue image is split from background, so that signature analysis subsequently based on batten Snakes (Snakes) model.

Background technology

Being commonly used in image processing field and tongue picture, to cut apart correlation technique as follows:

It is tongue image tongue body Region Segmentation that tongue picture is cut apart, and is a kind of concrete application of image partitioning method.Traditional image Segmentation adopts rim detection, region clustering scheduling algorithm, these methods all are to utilize the low-level feature of image, be the homogeneity or the mutability of pictorial data, and do not have to utilize the relevant priori of cutting apart target, as the position of target, size, shape etc.These methods need be carried out the integrity profile that complicated aftertreatment could be determined tongue body.And, often be difficult to obtain gratifying segmentation result owing to the reasons such as difference of contour feature and image quality.

Snakes (Snakes) model claims active contour model (active contour model) again, is proposed in 1987 by people such as Kass.Snakes (Snakes) is a kind of method that the skeleton pattern and the image feature of target are complementary, it utilizes the polygon of object to represent, target is formulated as a suitable energy function E, E is minimized obtain desired outline line then, thereby be partitioned into the target in the image.Snakes (Snakes) is a kind of batten of energy minimization, under the effect of various power and constraint condition elastic deformation takes place, up to the profile that obtains expecting.Its energy is generally become by three kinds of Lik-Sangs: its shape of internal force constraint, and its behavior of external force guiding, visual power drags it to significant image feature; The outline line of Snakes is locked near the image feature, exactly with its minimization.Like this, when seeking significant image feature, higher layer mechanism may be carried out with model by image feature being pushed to a suitable Local Extremum alternately.The maximum characteristics of Snakes (Snakes) are low-level feature and the high-rise knowledge that combines image, when being used for image Segmentation, all are better than classic method at aspects such as robustness, degree of accuracy, practicality.

Usually, Snakes is controlled simultaneously by several different acting forces, and each power produces an energy term.Can be expressed as

E_{snake} (V) = Σ_{i = 1}^{n} E_{snake} (v_{i}) = Σ_{i = 1}^{n} [E_{internal} (v_{i}) + E_{image} (v_{i}) + E_{extrnal} (v_{i})]

E wherein _InternalBe called internal energy, do not rely on pictorial data, only relevant with the shape facility of profile, be used for calculating the characteristic that some we are paid close attention to of contour shape, for example continuity and flatness; E _ImageBeing called picture power, is that the interaction of geometric model and pictorial data produces, at interested characterizing definition in the image, for example: edge, line, zone, texture etc.; E _ExternalBe external energy, represent the constraint condition of various artificial definition.

Batten Snakes as the reference mark, defines a SPL with this with one group of discrete coordinates point, and these points have provided the general shape of curve.Batten is a SPL, be with a series of polynomial curve sections form continuously, the curve of fairing.On mathematics, batten is a set of segmentation smooth function, is used for being similar to or the interpolative data point set.The represented curve of batten Snakes be resolve, can be little, and local detail can be described.Can resolve how much derivative characteristics of finding the solution it, be convenient to the calculating of energy function.

The whole process that adopts Snakes (Snakes) model to carry out image Segmentation is that an iteration optimization is up to the convergent process.In this process, need to solve three problems:

A) initialization of profile, b) design of energy function, c) optimisation strategy.

The initialization of profile will be determined the initial position of point and the original shape and the size of target, adopts the interactive means manual drawing usually.

Optimisation strategy has determined the speed of iteration convergence.Optimize is exactly by calculating the internal energy and the external energy of initial estimation profile, constantly attributes such as the position of this estimation profile, shape are upgraded according to certain rule, till profile satisfied some predetermined constraint conditions, this was the process of an iteration.Here, can be at a certain size search window of one of the definition of each reference mark on the profile, the point of selecting to have minimum Snakes energy in each search window replaces original reference mark as new profile reference mark, and the rest may be inferred, up to satisfying stopping criterion for iteration.

Optimization is the important step that Snakes finds the solution.The initial estimation profile approaches to profile to be measured in optimizing process gradually, optimizes when finishing, and estimates that profile converges on the desired destination profile.Optimized Algorithm commonly used has: the variational method, dynamic programming, Greedy algorithm, simulated annealing etc., wherein the Greedy algorithm is most widely used method.

The Greedy method is a kind of improved dynamic programming method.It realizes the locally optimal solution of energy function, and time complexity only has O (nm).Therefore computing velocity is fast, and storage demand is less.To each some v _i, its iterative step is as follows:

1) calculates E _Snake(v _i);

2) with v _iOther p in some m * m neighborhood _Jk, j, k ∈ [1, m] replaces v _iPoint calculates E respectively _Snake(p _Jk), j, k ∈ [1, m];

3) note E _Min=min (E _Snake(p _Jk), j, k ∈ [1, m]), if E _Snake(v _i)＜E _Min, v then _iPoint is constant; Otherwise with v _iPoint moves to corresponding to E _MinThe neighborhood point.

The stop criterion of iteration is: the mobile or iterations that no longer produces the reference mark surpasses default maximal value.Fig. 6 is the synoptic diagram of Greedy algorithm, v among the figure _iBe initial point, v _i' be corresponding to E _MinThe neighborhood point.Adopt 9 neighborhoods among the figure.

In image processing, because the condition difference of picture-taking, the parameter in the disposal route may be according to the actual conditions adjustment.The method of adjusting is, from the image that the same terms is taken, takes out a width of cloth or a few width of cloth, by experiment or trial method determine the occurrence of parameter.It also is like this adopting Snakes (Snakes) model to carry out image Segmentation.

Summary of the invention

The present invention just is based on above-mentioned Study on Technology, and the tongue body profile auto-initiation method based on Gray Projection and rigid template has realized cutting apart automatically of tongue image.

For with the tongue body zone automatically, split accurately and rapidly, the present invention has designed a kind of tongue body region segmentation method based on Snakes (Snakes) model.This method has been considered the characteristics such as color distortion of the shape, position, size of tongue body and tongue body zone and background area, and the design energy function carries out the profile initialization, and adopt easy, Local Optimization Algorithm to be to reach practical fast.Technical thought of the present invention is characterised in that:

1, according to the statistical study to the tongue body shape, defining one is the tongue body profile template of outer boundary with the rectangular area.By introducing this tongue body template, when cutting apart, added priori, as close as possible real tongue body profile in the time of can making the contour curve initialization about the tongue body shape.

2, adopt the Gray Projection analytic approach, obtain a rectangular area, the approximate location and the size of tongue body determined in this zone.

3, a kind of tongue body profile initial method based on Gray Projection and rigid template is proposed.

4, the priori that in the energy function of Snakes (Snakes) model, has added relevant tongue body profile.

5, through after tongue body profile initialization and having defined energy function, adopt Catmull-Rom batten Snakes (Snakes) model representation tongue body profile, and adopt existing Greedy method to be optimized, thus in colored tongue image, obtain the tongue body profile, be partitioned into the tongue body zone.

Technical scheme of the present invention is referring to Fig. 1, Fig. 2.The computing machine dividing method of this traditional Chinese medical science tongue picture based on batten Snakes (Snakes) model, be to finish the collection tongue image by digital camera, and the optical signalling of tongue body and colour code is converted to the electric signal image is input to computing machine and handles, operations such as transmission, it is characterized in that Computer Processing mainly is by USB interface software, on batten Snakes (Snakes) model based, tongue image is carried out read/write process, tongue image after the processing or tongue image carried out outputing to buffer after the dividing processing, through the display display result, it comprises the steps: successively

1) computing machine reads in the tongue image signal from USB interface, and is kept in the internal memory.The weighting parameter γ that energy in the Snakes model is calculated simultaneously ₁, γ ₂, α, β and iteration optimization algorithms maximum iteration time carry out initialization, the value of four parameters is obtained by trial method.

2) tongue image is carried out conversion, strengthening tongue body and the contrast between the background on every side, and color image is become gray scale image, conversion is carried out at each pixel, and transformation for mula is:

I (x, y) = \frac{R (x, y) - G (x, y)}{| G (x, y) - B (x, y) | + 1}

R in the formula (x, y), G (x, y) and B (x y) is the original red, green, blue tristimulus values of pixel, and (x y) is the gray-scale value after the conversion to I.

Because we find that three chroma color value R, G, the B of tongue image pixel have following rule: the G value on the skin is greater than the G value at tongue edge, the G value on the tongue edge usually and the B value difference seldom or bigger, the G value on skin is then all greater than the B value; The R value of tongue and skin is all greater than G value and B value.According to these color component values relative nature to each other, for strengthening the gray difference of tongue body profile and background, we adopt the intensity transformation function of above tongue image.Through such conversion, the gray-scale value of tongue body part is higher, and the part gray-scale value beyond the tongue body is relatively low.

3) enter based on Gray Projection and rigid template, initialized profile initialization subroutine is carried out at batten Snakes (Snakes) model silhouette reference mark: promptly adopt the Gray Projection analytic approach, obtain a rectangular area, the approximate location and the size of tongue body determined in this zone.Earlier according to strengthening visual level and the gray scale of vertical direction or the feature of brightness projection, determine the border of a rectangular area, obtain 4 borders up and down of rectangular area thus, thereby the position and the size in tongue body zone have been determined, after having determined tongue body zone square boundary, calculating tongue body profile template is the rigidity deformation parameter λ on border at home and abroad, and then definite initial control point and profile, thereby finishes the auto-initiation of batten Snakes (Snakes) model.

4) be outstanding tongue body, make things convenient for the picture power of successive iterations process to calculate,, be divided into following a few step the line nonlinearity conversion of going forward side by side of tongue image thresholding:

1. to 2) in the enhancing image ask the maximal value maxI of gray-scale value, mean value meanI, and calculate maximum difference dI=maxI-meanI;

2. be threshold value with meanI,, will be changed to 0 less than the gray-scale value of meanI strengthening image thresholdingization;

3. the image behind the thresholding is carried out nonlinear transformation, transformation for mula is:

U (x, y) = {(\frac{I (x, y) - meanI}{dI})}^{γ}

Exponent gamma in the formula is the nonlinear transformation parameter.

5) with the Greedy iteration optimization algorithms batten Snakes (Snakes) model is found the solution, solution procedure as previously mentioned, up to satisfying end condition: the position at an iteration rear profile reference mark no longer changes, or iterations reaches certain default maximal value, the iteration optimization subroutine call of profile reference mark finishes, obtain the final position at tongue body profile reference mark, adopt general Catmull-Rom spline interpolation formula to carry out spline interpolation, can obtain continuous tongue body contour curve.

6) adopt general Catmull-Rom spline interpolation formula to carry out spline interpolation, obtain continuous profile; The energy minimization of Snakes (Snakes) is to carry out on sparse discrete point, in order to obtain the continuous profile of target, need carry out interpolation and obtain accurate, continuous outline line.

7) will be positioned at by usual method that three chroma color values of pixel are changed to (255,255,255) (white) on the tongue body contour curve, save as destination file and output.

In addition according to the computing machine dividing method of above-described traditional Chinese medical science tongue picture based on batten Snakes (Snakes) model, wherein initialized profile initialization subroutine is carried out at batten Snakes (Snakes) model silhouette reference mark and is characterised in that, divide five stepping road wheels wide initialization:

1) on the basis that strengthens image, carry out the Gray Projection of horizontal direction, the characteristics of utilizing tongue body area grayscale projection value obviously to increase are from the middle part of projection, search for the position that first projection value reduces suddenly respectively left, to the right, obtain the border, the left and right sides of rectangular area;

2) center on border, the left and right sides is decided to be horizontal central line, and near the regional area the center line is defined as the center;

3) center is carried out the Gray Projection of vertical direction, because significant change often takes place near the enhancing gray-scale value the tongue body district lower boundary, so lower boundary is corresponding to the first order derivative maximal value of projection value;

4) center is carried out raw image brightness value (i.e. (R+G+B)/3) projection of vertical direction, owing to there is shade under the lip, the coboundary in tongue body zone is corresponding to the minimum value of projection value;

5) after above step is determined square boundary, according to the rigidity deformation parameter on border, tongue body profile template China and foreign countries, determine the initial position at profile reference mark, the computing method of deformation parameter are: the long L of being of outer boundary rectangle that establishes rigid template ₀, wide is W ₀, be respectively by above four positions in tongue image that go on foot the rectangle left and right sides up-and-down boundary that obtains: l ₁, r ₁, t ₁, b ₁, then the rectangular area is long is L=r-l, and wide is W=b-t, and deformation parameter is so: λ=(λ _l, λ _w), λ _l=L/L ₀, λ _w=W/W ₀, because the position, reference mark of profile template is that promptly the top left corner apex with this rectangle is coordinate center (0,0) with respect to the definition of outer boundary rectangle, so be (x if establish the coordinate position at i profile reference mark in the template _0i, y _0i), the coordinate at the initialization profile reference mark that then obtains is:

x _i＝l+λ _lx _0i

y _i＝t+λ _wy _0i。

In addition the computing machine dividing method according to above-described traditional Chinese medical science tongue picture based on batten Snakes (Snakes) model is characterised in that: internal energy adopts common version, when the computational picture energy, at first the raw image thresholding is gone forward side by side the line nonlinearity conversion with outstanding tongue body, according to image intensity behind the thresholding and gradient calculation picture power, internal energy and picture power sum are the gross energy of Snakes (Snakes) model then.

For a certain profile reference mark v _i, consider that tongue body profile in the tongue image meets the hypothesis of continuity and flatness, internal energy adopts common version, that is:

E _internal(v _i)＝α(v _i)E _elas(v _i)+β(v _i)E _bend(v _i)

E_{elas} (v_{i}) = {| \frac{&PartialD; V}{&PartialD; s} |}^{2} \approx \frac{{| v_{i} - v_{i - 1} |}^{2}}{d s^{2}} = \frac{{(x_{i} - x_{i - 1})}^{2} + {(y_{i} - y_{i - 1})}^{2}}{d s^{2}}

E_{bend} (v_{i}) = {| \frac{{&PartialD;}^{2} V}{&PartialD; s^{2}} |}^{2} \approx \frac{{| v_{i - 1} - 2 v_{i} + v_{i + 1} |}^{2}}{d s^{4}} = \frac{{(x_{i - 1} - 2 x_{i} + x_{i + 1})}^{2} + {(y_{i - 1} - 2 y_{i} + y_{i + 1})}^{2}}{d s^{4}}

Wherein weighting parameter α, β control the degree of restraint to continuity and flatness respectively.

Picture power is

E _image(v _i)＝γ ₁U(v _i)+γ ₂|U(v _i))| ²

Weighting parameter γ wherein ₁, γ ₂Control is to I (x, y) strength constraint and the gradient constraint of profile region; γ ₁, γ ₂Be made as negative value, make the maximum value that energy-minimum levels off to and the maximum value of gradient response,

External energy E _External=0,

Total energy function is expressed as

E (v_{i}) = α \frac{{(x_{i} - x_{i - 1})}^{2} + {(y_{i} - y_{i - 1})}^{2}}{d s^{2}} + β \frac{{(x_{i - 1} - 2 x_{i} + x_{i + 1})}^{2} + {(y_{i - 1} - 2 y_{i} + y_{i + 1})}^{2}}{d s^{4}}

+ γ_{1} U (v_{i}) + γ_{2} | &dtri; U (v_{i})) |

Other illustrates 2 points:

1, in the image processing, for some feature of outstanding concrete image, usually will do some conversion to image, promptly chromatic value or the gray-scale value to visual pixel carries out computing, claims such image enhancement that is transformed to again.For example, three chroma color value R of tongue image pixel, G, B have following rule: the G value on the skin is greater than the G value at tongue edge, the G value on the tongue edge usually and the B value difference seldom or bigger, the G value on skin is then all greater than the B value; The R value of tongue and skin is all greater than G value and B value.According to these color component values relative nature to each other, be to strengthen the gray difference of tongue body profile and background, we adopt tongue image intensity transformation function I (x, y):

I (x, y) = \frac{R (x, y) - G (x, y)}{| G (x, y) - B (x, y) | + 1}

The nonlinear transformation of being carried out when the calculating energy function also is based on same reason, and introducing exponential transform is in order to give prominence to the contrast of tongue body and skin more.

2, the initialization of profile will be determined the initial position of point and the original shape and the size of target, adopts the interactive means manual drawing usually.Owing to the tongue body that will cut apart at native system in the tongue image, if can determine approximate location, size and the shape of tongue body automatically, then the profile initialization can be carried out automatically.The present invention just is based on such consideration, and the tongue body profile auto-initiation method based on Gray Projection and rigid template has realized cutting apart automatically of tongue image.Energy function will design according to image and the characteristics of cutting apart target.

Effect of the present invention is seen Fig. 7, Fig. 8.Adopt as can be seen based on batten Snakes (Snakes) model, and, can obtain tongue body profile accurately automatically in conjunction with the characteristics of tongue image.Do not need manual initialization, thereby created condition for subsequently accurate tongue picture analysis.

Description of drawings

Fig. 1 is a traditional Chinese medical science tongue picture segmenting system block diagram.

1, digital camera, 2, USB interface, 3, computer processor, 4, output buffers, 5, tongue body cuts apart, 6, display, 7, segmentation result;

Fig. 2 is the inventive method main program flow chart;

Fig. 3 is a profile initialization subroutine process flow diagram in the inventive method;

Fig. 4 is an iteration optimization subroutine flow chart in the inventive method;

Fig. 6 is a Greedy iteration optimization synoptic diagram among the present invention;

Fig. 7 is the initialization procedure example of profile

(a) horizontal Gray Projection, center line and center signal among the figure; (b) horizontal Gray Projection and left and right border signal; (c) first order derivative of vertical Gray Projection and lower boundary signal; (d) vertical color brightness projection and coboundary signal; (e) initialization result;

Fig. 8 is colored tongue image of a width of cloth and a segmentation result (white line is represented outline line) thereof among the present invention;

Fig. 9 is system's main program flow chart that the inventive method is moved on computers;

Figure 10 is the profile initialization subroutine process flow diagram that the inventive method is moved on computers;

Figure 11 is the iteration optimization subroutine flow chart that the inventive method is moved on computers.

Embodiment

In the traditional Chinese medical science tongue picture segmenting system block diagram of Fig. 1, digital camera and USB interface all are commercially available, mainly finish the collection tongue image, the optical signalling of tongue body and colour code is converted to visual electric signal is input to computing machine, are convenient to operations such as Computer Processing, transmission; Computer Processing mainly is by USB interface software tongue image to be carried out read/write process; Tongue image after the processing outputs to buffer, is convenient to show; Display is the output device of image, and human eye is watched raw image by display and cut apart the back image; It is that tongue image to computing machine reads in carries out dividing processing that tongue body is cut apart, the output result.Original tongue image can be the image that collects in real time by digital camera, also can be to realize by being kept at the image in the hard disc of computer after the digital camera collection.The tongue body segmenting system is finished following master routine in computing machine, referring to Fig. 8, Fig. 9:

1, under coloured target situation: initiation parameter l, r, t, b, δ, γ, α, β, γ ₁, γ ₂, w, N and tongue body template.Three color lump bars of Fig. 8 periphery) and the part more than the upper lip wherein l, r, t, b are default value, are in order to remove color scale space 9 colour codes:.Their value can be determined according to a width of cloth tongue image in advance.δ is a threshold value of asking border, the left and right sides used.Set in advance according to trial method.δ among the present invention=0.2.γ is the parameter that nonlinear transformation adopted, and establishes γ=0.15 herein.α, β, γ ₁, γ ₂Be the energy calculated weighting coefficient of Snakes (Snakes), the value of four parameters is obtained by trial method.Can be made as respectively in the present invention: α=0.5, β=3.0, γ ₁=-0.2, γ ₂=-1.0.The width of window was established w=3 when w was Snakes (Snakes) iteration optimization among the present invention.The maximum iterations of setting when N is iteration optimization, N=200 among the present invention.The tongue body template is represented with an array of representing a relative coordinate.Under colourless target situation: initiation parameter l=0, t=0, b are that image is high, and r is the figure image width.

2, tongue image is carried out conversion.The conversion individual element carries out.Transformation for mula is:

I (x, y) = \frac{R (x, y) - G (x, y)}{| G (x, y) - B (x, y) | + 1} .

3, tongue body profile initialization.Be divided into following each step:

The first step: calculate the horizontal direction projection that strengthens image.As previously mentioned, (x y) has the capable w row of h to strengthen visual I.Be listed as row since l, calculate the gray-scale value sum S that each lists all pixels (r-l+1 pixel altogether) up to r _i,

S_{i} = Σ_{i = t}^{b - 1} I (i, j)

Obtain an array S, S=[S ₁, S ₂... S _i... S _r], this array promptly represents to strengthen the horizontal direction Gray Projection of image.Wherein l, r, t, b are default value, are in order to remove color scale space and the part more than the upper lip, to simplify the color characteristics of calculating and making full use of aforementioned tongue body, and are not subjected to the influence of color scale space.Their value can be determined according to a width of cloth tongue image in advance.

Second step: the characteristics of utilizing the projection of tongue body area grayscale obviously to increase, the border, the left and right sides of acquisition rectangular area.Method is:

From half j=[n/2 of projection array] beginning, first is less than δ to left search (promptly making j reduce 1) at every turn _lS _jWherein [n/2] expression rounds n/2.If promptly

S _j＜δ _l (0＜j＜[n/2])

Straight line x=l then ₁, l ₁=j+l is decided to be the left margin of rectangular area.

From half j=[n/2 of projection array] beginning, first reaches in δ to right-hand search (promptly making j increase 1) at every turn _rS _jIf promptly

S _j＜δ _l ([n/2]+1＜j＜r-l+1)

Straight line x=r then ₁, r ₁=j+l is decided to be the left margin of rectangular area.

The border promptly stops at the search in this zone after determining.In the formula, δ _l, δ _rBe preset threshold value, establish δ at this _l=δ _r=δ (maxS-minS)+minS.MaxS, minS are respectively maximum, the minimum value of horizontal projection.δ sets in advance.δ among the present invention=0.2.

The 3rd step: with the center line x=[(l on border, the left and right sides ₁+ r ₁)/2] be decided to be horizontal central line, near the regional area the center line is defined as the center.If the width of central area is w ₁, promptly from [(l ₁+ r ₁)/2]-w ₁To [(l ₁+ r ₁)/2]+w ₁Be the center.The width of central area can be decided to be half of border, left and right sides difference.

The 4th step: determine the rectangular area lower boundary.As previously mentioned, the Gray Projection of vertical direction is carried out in the center, because significant change often takes place near the enhancing gray-scale value the tongue body district lower boundary, so lower boundary is corresponding to the first order derivative maximal value of projection value.Method computing center district vertical direction projection by the above-mentioned first step.If the vertical projection array is P, P=[P ₁, P ₂... P _i... P _r], then the computing method of first order derivative are:

P _i′＝P _i-P _i-1，0＜i＜h

Ask the maximal value of first order derivative, according to aforementioned, the pairing position of first order derivative maximal value is lower boundary b ₁

The 5th step: raw image brightness value (i.e. (R+G+B)/3) the projection V of vertical direction is carried out in the center, and the pairing position of the minimum value of V is the coboundary t in tongue body zone ₁

The 6th step: calculate the deformation parameter of profile template,

λ＝(λ _l，λ _w)，λ _l＝L/L ₀，λ _w＝W/W ₀

Be calculated as follows the initial position at profile reference mark:

x _i＝l+λ _lx _0i

y _i＝t+λ _wy _0i

(x _0i, y _0i) be the coordinate position at i profile reference mark in the template.In the present invention, have 32 profile reference mark.These group data are kept in the array.

The profile initialization subroutine process flow diagram that Figure 10 moves on computers for the inventive method, Fig. 7 are the initialization procedure exemplary plot of profile.

4, to the line nonlinearity conversion of going forward side by side of tongue image thresholding.Be divided into following a few step:

1) the enhancing image that obtains in 2 is asked the maximal value maxI of gray-scale value, mean value meanI, and calculate maximum difference dI=maxI-meanI;

2) meanI is a threshold value, to strengthening image thresholdingization, will be changed to 0 less than the gray-scale value of meanI;

3) image behind the thresholding is carried out nonlinear transformation, transformation for mula is:

U (x, y) = {(\frac{I (x, y) - meanI}{dI})}^{γ}

Exponent gamma in the formula is the nonlinear transformation parameter, is obtained by trial method.γ=0.15 in the present invention.

5, to tongue body profile iteration optimization.

Iterative process is seen Figure 11, is described below:

1) reads in profile reference mark initial coordinate.I is changed to 0 with iterations, will indicate whether to have the variable bMove of reference mark shift in position to be changed to vacation;

2) read in the coordinate at a profile reference mark;

3) energy of each point (w * w point altogether) in the calculation control vertex neighborhood one by one in size is the search window of w * w, and ask least energy, and write down the coordinate of the pairing point of least energy.Among the present invention, search window adopts 3 neighborhoods, i.e. w=3.Computing formula at energy function:

E (v_{i}) = α \frac{{(x_{i} - x_{i - 1})}^{2} + {(y_{i} - y_{i - 1})}^{2}}{d s^{2}} + β \frac{{(x_{i - 1} - 2 x_{i} + x_{i + 1})}^{2} + {(y_{i - 1} - 2 y_{i} + y_{i + 1})}^{2}}{d s^{4}}

+ γ_{1} U (v_{i}) + γ_{2} | &dtri; U (v_{i})) |

In, ds=1, the value of four parameters is obtained by trial method, is respectively:

α＝0.5，β＝3.0，γ ₁＝-0.2，γ ₂＝-1.0。

4) this profile reference mark is moved to the energy smallest point.The coordinate that is about to this reference mark is revised as the coordinate of the pairing point of least energy.If the coordinate that reads in amended coordinate and the original coordinate (step 2)) different, make then that bMove is very, otherwise do not change the value of bMove;

5), then make iterations i increase by 1 if the profile reference mark disposes; Otherwise change two), handle next profile reference mark;

6) the true and false coordinate at reference mark that judges whether according to bMove changes.If no, then iteration finishes, return, otherwise;

7) judge that whether iterations i is less than default maximum iteration time N, if i＜N then changes two), carry out the next round iteration, otherwise the iteration end is returned.

6, carry out spline interpolation according to the reference mark coordinate and obtain continuous contour curve, can adopt different battens.

Adopt Catmull-Rom batten spline interpolation method among the present invention.

For example the Catmull-Rom batten is a kind of local interpolation batten, and its i section Catmull-Rom batten can be expressed as:

Q_{i} (τ) = ω_{i}^{1} (τ) Q_{i}^{1} (τ) + ω_{i}^{2} (τ) Q_{i}^{2} (τ)

ω wherein _i ¹(τ), ω _i ²Be the linear bending function of batten (τ), be defined as:

Q _i ¹(τ) be interpolation v _I-1, v _i, v _I+1Second order polynomial, Q _i ²(τ) be interpolation v _I-1, v _i, v _I+1Second order polynomial, be defined as respectively:

Q_{i}^{1} (τ) = v_{i - 1} + (τ - τ_{i - 1}) (\frac{- v_{i - 1} + v_{i}}{- τ_{i - 1} + τ_{i}} + \frac{(τ - τ_{i}) (- \frac{- v_{i - 1} + v_{i}}{- τ_{i - 1} + τ_{i}} + \frac{- v_{i} + v_{i + 1}}{- τ_{i} + τ_{i + 1}})}{- τ_{i - 1} + τ_{i + 1}})

Q_{i}^{2} (τ) = v_{i} + (τ - τ_{i}) (\frac{- v_{i} + v_{i + 1}}{- τ_{i} + τ_{i + 1}} + \frac{(τ - τ_{i + 1}) (- \frac{- v_{i} + v_{i + 1}}{- τ_{i} + τ_{i + 1}} + \frac{- v_{i + 1} + v_{i + 2}}{- τ_{i + 1} + τ_{i + 2}})}{- τ_{i} + τ_{i + 2}})

Non-homogeneous parametric method is adopted in the definition of the parameter τ of batten model, makes it be proportional to Euclidean distance between the reference mark, and recursion formula is:

\frac{τ_{i} - τ_{i - 1}}{τ_{i + 1} - τ_{i}} = | | \frac{v_{i} - v_{i - 1}}{v_{i + 1} - v_{i}} | |

Optional τ ₁=0 and τ _n=1.

And the outline line that will finally obtain is represented (tristimulus values that are about to this pixel are changed to (255,255,255)) with white line.

7, output segmentation result

Fig. 8 is a width of cloth tongue image segmentation result.

Claims

1. The computerized tongue image segmentation method based on the spline Snakes model is to collect the tongue image by a digital camera, and convert the optical signal of the tongue body and the color code into an image electrical signal and input it to the computer for further processing. Processing, transmission and other operations, the method is characterized in that the computer processing is mainly to read/write the tongue image through the USB interface software, and the processed tongue image is segmented on the basis of the spline Snakes (Snakes) model After output to the register, the result is displayed on the monitor, which includes the following steps in turn:

1) The computer reads the tongue image signal from the USB interface and saves it in the memory; at the same time, the weight parameters γ ₁ , γ ₂ , α, β and the maximum iteration number of the iterative optimization algorithm in the Sinex model are calculated Initialize, the values of the four parameters are obtained by heuristics,

2) Transform the tongue image to enhance the contrast between the tongue body and the surrounding background, and change the color image into a grayscale image. The transformation is carried out for each pixel. The transformation formula is:

I I ((x x,, y the y)) = = \frac{R R ((x x,, y the y)) - - G G ((x x,, y the y))}{| | G G ((x x,, y the y)) - - B B ((x x,, y the y)) | | + + 11}

In the formula, R(x, y), G(x, y) and B(x, y) are the original red, green and blue color values of the pixel, and I(x, y) is the transformed gray value;

3) Enter the outline initialization subroutine based on grayscale projection and rigid template to initialize the outline control points of the spline Snakes model: that is, use the grayscale projection analysis method to obtain a rectangular area, which determines the For the approximate position and size of the tongue body, first determine the boundary of a rectangular area according to the characteristics of the grayscale or brightness projection in the horizontal and vertical directions of the enhanced image, and thus obtain the four boundaries of the upper, lower, left, and right sides of the rectangular area, thereby determining the tongue body The position and size of the area, after determining the rectangular boundary of the tongue area, calculate the rigid deformation parameters of the outer boundary in the tongue outline template, and then determine the initial control points and outline, so as to complete the spline Snakes (Snakes) model automatic initialization;

4) Thresholding the tongue image and performing nonlinear transformation is divided into the following steps:

1. the enhanced image in 2) is asked for the maximum value maxI of the gray value, the average value meanI, and calculates the maximum difference dI=maxI-meanI;

2. take meanI as the threshold value, thresholding the enhanced image, and setting the gray value less than meanI to 0;

③ Perform nonlinear transformation on the thresholded image, the transformation formula is:

U u ((x x,, y the y)) = = {((\frac{I I ((x x,, y the y)) - - meanI meanI}{dI iGO}))}^{γ γ}

The exponent γ in the formula is a nonlinear transformation parameter;

5) Use the Greedy iterative optimization algorithm to solve the spline Snakes model. The general method is used for the solution step until the termination condition is met, and the position of the contour control point does not change after one iteration, or the number of iterations reaches a certain value. A preset maximum value, the contour control point iterative optimization subroutine is called, and the final position of the tongue contour control point is obtained, and the general Catmull-Rom spline interpolation formula is used for spline interpolation to obtain a continuous tongue body contour curve;

6) The general Catmull-Rom spline interpolation formula is used for spline interpolation to obtain continuous contours;

7) Set the three-color chromaticity value of the pixel on the tongue contour curve to (255, 255, 255) (white) according to the usual method, save it as a result file and output it.

2, the traditional Chinese medical science tongue image computer segmentation method based on spline Si Nikes (Snakes) model according to claim 1, wherein the contour initialization subroutine that spline Si Nex (Snakes) model contour control point is initialized is characterized by contour initialization in five steps:

1) On the basis of enhancing the image, carry out horizontal grayscale projection, using the characteristics of the tongue body area grayscale projection being significantly higher, starting from the middle of the projection, search for the first projection to the left and right and suddenly decrease , get the left and right boundaries of the rectangular area;

2) The center of the left and right boundaries is defined as the horizontal midline, and the local area near the midline is defined as the central area;

3) The central area is grayscale projected in the vertical direction. Since the enhanced grayscale value near the lower boundary of the tongue body often changes significantly, the lower boundary corresponds to the maximum value of the first derivative of the projection value;

4) Project the original image luminance value (i.e. (R+G+B)/3) in the vertical direction to the center area, because there is a shadow under the lip, the upper boundary of the tongue body area corresponds to the minimum value of the projection value;

5) After determining _the rectangular boundary in the above steps, determine the initial position of the contour control point according to the rigid deformation parameters of the outer boundary in the tongue contour template. W ₀ , the positions of the left and right upper and lower boundaries of the rectangle obtained in the above four steps in the tongue image are: l ₁ , r ₁ , t ₁ , b ₁ , then the length of the rectangular area is L=rl, and the width is W=bt , then the deformation parameters are: λ=(λ _l , λ _w ), λ _l ＝L/L ₀ , λ _w ＝W/W ₀ , since the position of the control point of the contour template is defined relative to the outer boundary rectangle, that is, the The upper-left vertex of the rectangle is the coordinate center (0, 0), so if the coordinate position of the i-th contour control point in the template is set to (x _0i , y _0i ), the coordinates of the initialized contour control point obtained are:

x _i ＝l+λ _l x _0i

y _i =t+λ _w y _0i .

3. The computerized method for segmenting tongue images in traditional Chinese medicine based on the spline Snakes (Snakes) model according to claim 1 is characterized in that: the internal energy adopts a general form, and when calculating the image energy, at first the original image Thresholding and performing nonlinear transformation to highlight the tongue, then calculating the image energy based on the thresholded image intensity and gradient, the sum of internal energy and image energy is the total energy of the Snakes model;

For a contour control point v _i , the internal energy adopts a general form, namely: E _internal (v _i )=α(v _i )E _elas (v _i )+β(v _i )E _bend (vi)

{E E.}_{elas elas} (({v v}_{i i})) = = {| | \frac{&PartialD; &PartialD; V V}{&PartialD; &PartialD; s the s} | |}^{22} \approx \approx \frac{{| | {v v}_{i i} {- - v v}_{i i - - 11} | |}^{22}}{{ds ds}^{22}} = = \frac{{(({x x}_{i i} - - {x x}_{i i - - 11}))}^{22} + + {(({y the y}_{i i} - - {y the y}_{i i - - 11}))}^{22}}{{ds ds}^{22}}

{E E.}_{bend bend} (({v v}_{i i})) = = {| | \frac{{&PartialD; &PartialD;}^{22} V V}{{&PartialD; &PartialD; s the s}^{22}} | |}^{22} \approx \approx \frac{{| | {v v}_{i i - - 11} - - 22 {v v}_{i i} + + {v v}_{i i + + 11} | |}^{22}}{{ds ds}^{22}} = = \frac{{(({x x}_{i i - - 11} - - {22 x x}_{i i} + + {x x}_{i i + + 11}))}^{22} + + {(({y the y}_{i i - - 11} - - 22 {y the y}_{i i} + + {y the y}_{i i + + 11}))}^{22}}{{ds ds}^{44}}

Among them, the weight parameters α and β respectively control the degree of constraint on continuity and smoothness,

The image energy is:

E _image (v _i )＝γ ₁ U(v _i )+γ ₂ |U(v _i ))| ²

Among them, the weight parameters γ ₁ and γ ₂ control the I(x, y) intensity constraint and gradient constraint on the area where the contour is located, and γ ₁ and γ ₂ are set to negative values, so that the energy minimum value approaches the maximum value and the gradient The maximum value of the response,

External energy E _external ＝0

The total energy function is expressed as:

E E. (({v v}_{i i})) = = α α \frac{{(({x x}_{i i} - - {x x}_{i i - - 11}))}^{22} + + {(({y the y}_{i i} - - {y the y}_{i i - - 11}))}^{22}}{{ds ds}^{22}} + + β β \frac{{(({x x}_{i i - - 11} - - 22 {x x}_{i i} + + {x x}_{i i + + 11}))}^{22} + + {(({y the y}_{i i - - 11} - - 22 {y the y}_{i i} + + {y the y}_{i i - - 11}))}^{22}}{{ds ds}^{44}}

+ γ_{1} u (v_{i}) + γ_{2} | &dtri; u (v_{i})) |

.