The preferred embodiment and other aspects of the invention will become apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings, which are provided for the purpose of describing embodiments of the invention and not for limiting same, in which:
The application scenario of the directed feature development method is shown in
In one embodiment of the invention, the initial features 106 include
The initial features 106 along with the initial feature list 102, the learning image 100 and the object masks 104 are processed by the interactive feature enhancement step 114 of the invention to generate feature recipe 108. In one embodiment of the invention, the feature recipe contains a subset of the salient features that are selected as most relevant and useful for the applications. In another embodiment of the invention, the feature recipe includes the rules for new feature generation.
The interactive feature enhancement method further consists of a visual profiling selection step for interactive salient feature selection and a contrast boosting step for new feature generation. The two steps could be performed independently or sequentially. The sequential processing flow is shown in
As shown in
The visual profiling selection method allows the input from human application knowledge through visual examination without the need for human's understanding of the mathematical formula underlying the feature calculation. The processing flow for the visual profiling selection method is shown in
The initial features contain the feature distributions for the learning objects. The information measurement method of this invention measures the information content of the feature distribution to generate at least one information score. In one embodiment of the invention, the information content such as coefficient of variation (standard deviation divided by mean) is used for the information score. In another embodiment of the invention, signal percentage is used as the information score measurement. The signal objects are objects whose feature values are greater than mean * (1+α) or are leas than mean * (1−α). Where α is a pre-defined factor such as 0.2.
When the objects are labeled as two classes, the one-dimensional class separation measures can be used for the information score. We can define between-class variance σ2b, within-class variance σ2w, and mixture class variance σ2m. Common class separation measures include S1/S2, ln|S1|−ln|S2|, sqrt(S1)/ Sqrt(S2), etc. Where S1 and S1 are one of between-class variance σ2b, within-class variance σ2w, and mixture variance σ2m (Keinosuke Fukunaga “Statistical Pattern Recognition”, 2nd Edition, Morgan Kaufmann, 1990 P. 446-447).
In another embodiment of the invention, the unlabeled data can be divided into two classes by a threshold. The threshold could be determined by maximizing the value:
(NL×mL2)+(NH×mH2)
where NL and NH are the object counts of the low and high sides of the threshold, and mL2, mH2 are the second order moments on the left and right sides of the threshold. After the two classes are created by thresholding, the above class separation measures could be applied for information scores.
Those ordinary skilled in the art should recognize that other information measurement such as entropy and discriminate analysis measurements could be used as information scores and they are all within the scope of the current invention.
The ranking method 322 inputs the information scores 300 of the features from the initial feature list 102 and ranks them in ascending or descending orders. This results in the ranked feature list 304 output.
The object sorting method 326 inputs the profiling feature 306 index and its associated initial features 106 for all learning objects deriving from the learning image 100 and the object masks 104. It sorts the objects according to their profiling feature values in ascending or descending order. This results in the sorted object sequence as well as their object feature values.
The processing flow for the object montage creation method is shown in
The object zone 400 for each of the objects are processed by an object montage synthesis step 406 that inputs the object sequence 308 to synthesize the object montage containing a plurality of object zones ordered by the object sequence 308 to form an object montage frame 402. An object montage frame 402 is a one-dimensional or two-dimensional frame of object zones where the zones are ordered according to the object sequence 308.
The object mintage frame 402 is processed by an object montage display creation step 408 that associates the object feature values 310 to the object montage frame 402. The object feature values 310 can be hidden or shown by user control through the user interface 324. Also, object zone(s) 400 are highlighted for the selected object(s) 318. The highlight includes either a special indication such as frame drawing or object mask overlay. The object montage frame 402 containing feature value association and selected object highlighting forms the object montage display 316 output.
The processing flow for the histogram method is shown in
The user interface step 324 of the invention displays the ranked feature list 304 and their information scores 300 and allows human 110 to select profiling feature 306 for object montage creation 330. The processing flow for the user interface is shown in
The contrast boosting method 208 of the invention allows user re-arrange objects on montage to specify extreme examples. This enables the utilization of application knowledge to guide feature selection. Initial features ranked by contrast between the user specified extreme examples are used for application specific feature selection. New features are generated automatically to boost the contrast between the user specified extreme examples for application specific feature optimization. The processing flow for the contrast boosting feature optimization method is shown in
This invention allows human 110 to specify extreme examples by visual examination of montage object zones and utilizing application knowledge to guide the re-arrangement of object zones. The extreme example specification 906 is performed by re-arranging the objects in an object montage display 316. In this way, human 110 can guide the new feature generation and selection but do not have to know the mathematics behind computer feature calculation. Human 110 is good at identifying extreme examples of distinctive characteristics yet human 110 is not good at discriminating between borderline cases. Therefore, the extreme example specification 906 requires only human to move obvious extreme objects to the top and bottom of the object montage display 316. Other objects do not have to be moved. In the extreme examples that are moved by human 110, human could sort them according to the human perceived strength of the extreme feature characteristics. The updated object montage display 316 after extreme example specification forms the updated montage 904 output. The updated montage output specifies three populations: extreme 1 objects, extreme 2 objects, and other unspecified objects.
The contrast boosting feature generation method automatically generates new features by combining a plurality of initial features to boost the contrast between the extreme examples.
In a particularly preferred, yet not limiting embodiment, the present invention uses two initial feature combination for new feature generation, three types of new features are generated:
The ordinary skilled in the art should recognize that the combination could be performed iteratively using already combined features as the source for new combination. This will generate new features involving more than two initial features without changing the method. To assure that there is no division by zero problem, in one embodiment of the invention, the normalization combination is implemented in the following form:
Feature_1/(Feature_2+α)
Where α is a small non-zero value.
The processing flow for the contrast boosting feature generation is shown in
The updated montage 904 specifies three populations: extreme 1 objects, extreme 2 objects, and other unspecified objects. The population class construction 1102 generates three classes and associate them with the initial features. In the following, we call extreme 1 objects as class 0, extreme 2 objects as class 1, and the other objects as class 2.
For the new features with fixed combination rules such as:
Requires the determination of the boosting_factor. To determine the parameters, goodness metrics are defined.
The goodness metric for contrast boosting consists of two different metrics. The first metric (D) measures the discrimination between class 0 and class 1. The second metric (V) measures the distribution of the class 2 with respect to the distribution of the class 0 and class 1. The metric V estimates the difference between distribution of the class 2 and the distribution of the weighted mean of the class 0 objects and class 1 objects. In one embodiment of the invention, the two metrics include discrimination between class 0 and class 1 (D) and class 2 (V) difference as follows:
where m0, m1, and m2 are mean of the class 0, class 1, and class 2, and σ0, and σ1, and σ2 are the standard deviation of the class 0, class 1, and class 2, respectively. The parameter w is a weighting factor for the population of the classes and the parameter v is a weighting value for the importance of the class 0 and class 1. In one embodiment of the invention, the value of the weight w is
In another embodiment of the invention, we set w=1 without considering the number of objects. In a preferred embodiment of the invention, the value of v is set to 0.5. This is the center of the distribution of the class 0 and class 1. Those ordinary skilled in the art should recognize that other values of w and v can be used and they are within the scope of this invention.
In a particularly preferred, yet not limiting embodiment, the goodness metric of the contrast boosting is defined so that it is higher if D is higher and V is lower. Three types of the rules satisfying the goodness metric properties are provided as non-limiting embodiment of the invention.
In one embodiment of the invention, the new feature generation rules are simply the selected initial features and pre-defined feature combination rules with its optimal boosting_factor values.
The boosting factor determination method determines the boosting factor for the best linear combination of two features: Feature_1+boosting_factor*Feature_2.
Let two features be f and g, the linear combined features can be written as
h=f+αg
From the above method, the mean, variance and covariance are
m
0
=m
0f
+αm
0g
m
1
=m
1f
αm
1g
m
2
=m
2
+αm
2g
σ02=σ0f2+2ασ0fg+α2σ0g2
σ12=σ1f2+2ασ1fg+α2σ0g2
σ11=σ2f2+2ασ2fg+α2σ2g2
Combining the above methods, the metric D can be rewritten as follows:
and its derivative as follows:
where
p
1
=m
0f
+m
1f
p
2
=m
0g
+m
1g
q
1
=wσ
0f
2+(1−w)σ1f2
q
2
=wσ
0fg+(1−w)σ1fg
q
3
=wσ
0g
2+(1−w)σ1g2
and metric v can be rewritten as follows:
and its derivative as follows:
where
r
1
=m
2f
−v
m
0f−(1−v)m1f
r
2
=m
2g
−v
m
0g−(1−v)m1g
s
1=σ2f2+v2σ0f2+(1−v)2σ1f2
s
2=σ2fg+v2σ0fg+(1−v)2σ1fg
3=σ2g2+v2σ0g2+(1−v)2σ1g2
The parametric method of finding a is under the Gaussian assumption. In many practical applications, however, the Gaussian assumption does not apply. In one embodiment of the invention, a non-parametric method using the area ROC (receiver operation curve) is applied.
In Gaussian distribution, the smaller area ROC (AR) is
AR=erfc(D)
where
From the above relationship, we could defined:
D=erf
−1(AR)
Therefore, the procedure to find the goodness metric D is
The best α is determined by maximizing the values in the above steps c, d, and e. In one embodiment of the invention, the operation of the erf−1(x) is used in table or inverse function of the sigmoid functions.
In the case that the ranking among the extreme examples is specified, one embodiment of the invention generates new features considering the ranks. The goodness metric include the integration of two metrics as follows:
JR1=E(1+γV)
JR2=EeγV
where E is the error estimation part of the metric and V is the class 2 part of the metric. The better feature is the one with smaller JR value.
The error estimation metric E for this case is simply related to the error of the ranks. When rank between 1 to LL and HH to N from the N objects are given, in one embodiment of the invention, the metric is
which uses only rank information. However, the rank misleads the contrast boosting result when feature values of the several ranks are similar. To overcome this problem, in another embodiment of the invention, the metric is
where fr is the feature value of the given rank r and {circumflex over (f)}r is the feature value of the sorted rank r. {circumflex over (f)}HQ and {circumflex over (f)}LQ are the feature values of top 25 and 75 percentile. The weight value wr can be used for the emphasis the specific rank. For example, wr=1 or
The rank of class 2 is meaningless, so the comparison of the ranking is not meaningful. Therefore, the metric of given class may be better. The procedure of this method is
The boosting factor can be determined by finding the best α to have minimum of the cost1/cost2 using the new feature f+αg .
The new features and the initial features are processed to generate goodness metric using the methods described above. The goodness metrics represent extreme directed measures. Therefore, the features are ranked according to the goodness metrics. This results in the extreme ranked features for displaying to human 110.
The feature display and selection 912 allows human 110 to select the features based on the extreme ranked features 902. The object montage display 316 of the selected features is generated using the previously described method. The object montage display 316 is shown to human 110 along with the new feature generation rules 204 and the generating features. After object montage display 316 reviewing, the human 110 makes the selection among the initial features 106 and the new features 900 for optimal feature selection. This results in the optimized features 202. The optimized features 202 along with their new feature generation rules 204 are the feature recipe output 108 of the invention.
The invention has been described herein in considerable detail in order to comply with the Patent Statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the inventions can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment details and operating procedures, can be accomplished without departing from the scope of the invention itself.