quantification of facial asymmetry for expression-invariant human identification
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Quantification of Facial Asymmetry for Expression-invariant Human
Identification
Yanxi Liu yanxi@cs.cmu.edu
The Robotics Institute School of Computer ScienceCarnegie Mellon University
Pittsburgh, PA USA
Acknowledgement• Joint work with Drs. Karen Schmidt and Jeff Cohn (Psychology, U. Of Pitt).• Students who work on the data as research projects: Sinjini Mitra, Nicoleta Serban, and Rhiannon Weaver (statistics, CMU), Yan Karklin, Dan Bohus (scomputer science) and Marc Fasnacht (physics).• Helpful discussions and advices provided by Drs. T. Minka, J. Schneider, B. Eddy, A. Moore and G. Gordon. • Partially funded by DARPA HID grant to CMU entitled:“Space Time Biometrics for Human Identification in Video”
Human Faces are Asymmetrical
Left Face Right Face
Under Balanced Frontal Lighting (from CMU PIE Database)
What is Facial Asymmetry?
• Intrinsic facial asymmetry in individuals is determined by biological growth, injury, age, expression …
• Extrinsic facial asymmetry is affected by viewing orientation, illuminations, shadows, highlights …
Extrinsic Facial asymmetry on an image is Pose-variantOriginal ImageLeft face Right Face
Facial Asymmetry Analysis• A lot of studies in Psychology has been done on
the topics of– attractiveness v. facial asymmetry (Thornhill &
Buelthoff 1999)– expression v. facial movement asymmetry
• Identification– Humans are extremely sensitive to facial asymmetry– Facial attractiveness for men is inversely related to
recognition accuracy (O’Toole 1998)
Limitations: qualitative, subjective, still photos
Motivations
• Facial (a)symmetry is a holistic structural feature that has not been explored quantitatively before
• It is unknown whether intrinsic facial asymmetry is characteristic to human expressions or human identities
The question to be answered in this work
How does intrinsic facial asymmetry affect human face identification?
DATA: Expression VideosCohn-Kanade AU-Coded Facial Expression Database
joy
anger
disgust
Neutral Peak
Sample Facial Expression Frames
Neutral
Joy
Disgust
Anger
Total 55 subjects. Each subject has three distinct expression videos of varied number of frames. Total 3703 frames.
Face Image Normalization
AffineDeformation based on 3 reference points
Inner canthus
Philtrum
Face Midline
Quantification of Facial Asymmetry1. Density Difference: D-face
D (x,y) = I(x,y) – I’(x,y)I(x,y) --- normalized face image, I’(x,y) --- bilateral reflection of I(x,y) about face midline
2. Edge Orientation Similarity: S-face
S(x,y) = cos(Ie(x,y),I’e(x,y))
where Ie, Ie’ are edge images of I and I’ respectively, is the angle between the two gradient vectors at each pair of corresponding points
Asymmetry Faces
Original D-face S-face
An half of D-face or S-face contains all the needed information. We call these half faces Dh, Sh,Dhx, Dhy,
Shx,Shy AsymFaces.
Asymmetry Measure Dhy for two subjects each has 3 distinct expressions
Joy | anger | disgust Joy anger | disgust
forehead
chin
forehead
chin
Dhy Dhy
temporalspatial
Forehead -- chin
Forehead -- chin
Forehead -- chin
temporalspatial
Forehead -- chin
Forehead -- chin
Forehead -- chin
spatial
Forehead -- chin
Forehead -- chin
Forehead -- chin
Evaluation of Discriminative Power of Each
Dimension in SymFace Dhy
Bridge of nose
forehead chin
Variance Ratio
Most Discriminating Facial Regions Found
Experiment Setup55 subjects, each has three expression video sequences (joy, anger, disgust). Total of 3703 frames. Human identification test is done on ----
Experiment #1: train on joy and anger, test on disgust;Experiment #2: train on joy and disgust, test on anger;Experiment #3: train on disgust and anger, test on joy;Experiment #4: train on neutral expression frames,test on peak Experiment #5: train on peak expression frames,test on neutral
The above five experiments are carried out using (1) AsymFaces, (2) Fisherfaces, and (3) AsymFaces and FisherFaces together.
Sample Results: Combining Fisherfaces (FF) with AsymFaces (AF)
(Liu et al 2002)
Data set is composed of 55 subjects, each has three expression videos.There are 1218 joy frames, 1414 anger frames and 1071 disgust frames. Total number of frames is 3703.
All combinations of FF and AF features are tested and evaluated quantitatively
Complement Conventional Face Classifier
107 pairs of face images taken from Feret database.It is shown that asymmetry-signature’s discriminating power demonstrated (1) has a p value << 0.001 from chance
(2) is independent from features used in conventional classifiers, decreases the error rate of a PCA classifier by 38% (15% 9.3%)
Quantified Facial Asymmetry used for Pose estimation
Summary
• Quantification of facial asymmetry is computationally feasible.•The intrinsic facial asymmetry of specific regions captures individual differences that are robust to variations in facial expression• AsymFaces provides discriminating information that is complement to conventional face identification methods (FisherFaces)
Future Work• (1) construct multiple, more robust facial asymmetry measures that can capture intrinsic facial asymmetry under illumination and pose variations using PIE as well as publicly available facial data. • (2) develop computational models for studying how recognition rates is affected by facial asymmetry under gender, race, attractiveness, hyperspectral variations.• (3) study pose estimation using a combination of facial asymmetry with skewed symmetry.
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