Utilizing Posterior Probability for Race-composite Age Estimation Early Applications to MORPH-II Benjamin Yip NSF-REU in Statistical Data Mining and Machine Learning for Computer Vision and Pattern Recognition The University of North Carolina at Wilmington
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Utilizing Posterior Probability forRace-composite Age EstimationEarly Applications to MORPH-II
Benjamin Yip
NSF-REU in Statistical Data Mining and Machine Learningfor Computer Vision and Pattern Recognition
The University of North Carolina at Wilmington
Presentation Outline
1. Introduction
2. MORPH-II
3. Image Pre-processing
4. Methods
5. Preliminary Results
6. Conclusions
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Introduction
The Importance of Age Estimation
The human face encodes a wealth of information about theindividual; when properly analyzed, this information becomesvaluable data that can be used in a wide array of applications [2]:
The human face encodes a wealth of information about theindividual; when properly analyzed, this information becomesvaluable data that can be used in a wide array of applications [2]:
The human face encodes a wealth of information about theindividual; when properly analyzed, this information becomesvaluable data that can be used in a wide array of applications [2]:
Previous research [3] has shown that age estimation is highlysensitive to race and gender categories. However, as far as we aware,no previous models have taken multiracial individuals into account.
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Project Overview
MORPH-IIPre-
processingGenderClsf.
Race ClassificationRace Classification
BM AgeEstimator
WM AgeEstimator
BF AgeEstimator
WF AgeEstimator
MaleFemale
Figure 1: The four subgroup age estimators correspond to: black females(BF), white females (WF), black males (BM) and white males (WM)
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Utilizing Posterior Probability
Let b,w ∈ [0, 1] be the posterior probabilities of belonging to eachrace, where b+ w = 1.
Pre-processing is a very important operation in computer visiontasks, as valuable information is usually enveloped in meaninglessspace. Accordingly, the absence of a pre-processing step can havedrastic consequences on the results.
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Pre-processing Objectives
Given a standardmugshot,
the objective is to:
1. ensure properrotation,
2. extract only theface, and
3. standardize theimage,
yielding thepre-processed face.
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Pre-processing MORPH-II
Figure 4: Stages of Pre-processing Figure 5: Challenging Images
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Methods
Subsetting
Given the heavily imbalanced nature of MORPH-II, only images ofBlack and White individuals were used in this project. These imageswere subsetted according to the below scheme:
bf_1 wf_1 bm_1 wm_1
bf_2 wf_2 bm_2 wm_2
f1
f2
m1
m2
Figure 6: Subsetting Scheme
In this reduced dataset there are a total of 20,560 images in a 3 to 1Male to Female ratio. The images for each gender are split into twohalves, and every race and gender subgroup is divided similarly (±1image). There are no common individuals between subsets.
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Feature Extraction
After undergoing histogram equalization to correct for illuminationvariation, features were extracted from each image using LocalBinary Patterns (LBPs); these feature vectors were used for all stagesof the age estimation pipeline.
Figure 7: Examples of LBPs1
A Note on Dimensionality ReductionThe dimension of the LBP feature vectors was reduced using Principal ComponentAnalysis (PCA). 400 principal components were kept.1http://scikit-image.org/docs/0.12.x/auto_examples/features_detection/plot_local_binary_pattern.html
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Race Classification
Race ClassifierSupport Vector Machine (SVM)with a linear kernel
• Used to obtain posteriorprobabilities
Table 3: Race Classification Accuracies
train : test Accuracy Cost
f1 : f2 96.03 .0002f2 : f1 95.97 .0001m1 : m2 96.01 .0001m2 : m1 98.13 .0001
Posterior probabilities are obtained by fitting a sigmoid/logisticmodel to the SVM outputs (Platt scaling) [4]:
P(y = 1 | f) = 11+ exp(Af+ B) (1)
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Age Estimation
ModelSupport Vector Regression (SVR)with a linear kernel
Race Classification
Black AgeEstimator
White AgeEstimator
YB YW
b w
Y∗ = (b ∗ YB) + (w ∗ YW)
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Preliminary Results
Partial Dataset
The Partial (even) dataset contains 1,000 images of 1,000 distinctindividuals; it differs from the reduced version of MORPH-II in thatthe overall age distribution is uniform.
While the results from the Partial dataset seem to show that thecomposite age estimate is an improvement over the straightforwardprediction, the preliminary results from the reduced MORPH-IIdataset are mixed. Much more work remains to be done in testingthe model on the full dataset.
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Future Work
The race labels do not account for multiracial individuals; therefore,there may be mixed race individuals in the training sets that arediluting the models. To correct for this:
1. Assemble training sets of individuals who are not of mixed race(i.e. they fall clearly into the Black or White race categories)
2. Use these sets to train race classifiers and age models
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Future Work
The race labels do not account for multiracial individuals; therefore,there may be mixed race individuals in the training sets that arediluting the models. To correct for this:
1. Assemble training sets of individuals who are not of mixed race(i.e. they fall clearly into the Black or White race categories)
2. Use these sets to train race classifiers and age models
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References i
G. Bingham, B. Yip, M. Ferguson, and C. Nansalo.MORPH-II: Inconsistencies and Cleaning.
Y. Fu, G. Guo, and T. S. Huang.Age synthesis and estimation via faces: A survey.IEEE Transactions on Pattern Analysis and Machine Intelligence,32(11):1955–1976, Nov 2010.
G. Guo and G. Mu.Human age estimation: What is the influence across race andgender?In 2010 IEEE Computer Society Conference on Computer Visionand Pattern Recognition - Workshops, pages 71–78, June 2010.
References ii
J. C. Platt.Probabilistic outputs for support vector machines andcomparisons to regularized likelihood methods.In ADVANCES IN LARGE MARGIN CLASSIFIERS, pages 61–74. MITPress, 1999.
K. Ricanek and T. Tesafaye.Morph: A longitudinal image database of normal adultage-progression.In Automatic Face and Gesture Recognition, 2006. FGR 2006. 7thInternational Conference on, pages 341–345. IEEE, 2006.