1. A 4-WEEK PROJECT IN Active Shape and Appearance Models
by Renée Anderson
and Vedrana Andersen

2. Overview Preprocessing (Renée) Building models (Vedrana)
Manipulating faces (Renée)
Active appearance models (Vedrana)
Tim Cootes

3. STATISTICAL MODELS Concept
Several steps developed by Cootes and Taylor:
Data capture and representation
Data normalization
Statistical analysis

4. For each object (face, heart, spine): Image Landmark points
PREPROCESSING Data
For each object (face, heart, spine):
Image
Landmark points
Faces, hearts, spines

5. PREPROCESSING Cropping and Translation
Cropping out the background
Center of gravity of landmark points in the center of image

6. PREPROCESSING Alignment
Allowed transformations: translation, rotation and scaling
Iterative method: aligning each shape with mean shape

7. PREPROCESSING Masking
For visualization
Leave inside of convex hull of landmark points

8. PREPROCESSING Warping
Mapping landmark points to mean shape
Tried two - piecewise linear - thin-plate spline

9. PREPROCESSING Gray-level Normalization
Applying scaling and offset to gray-level vectors (samples)
Iterative method: normalizing each gray-level vector with mean gray-level

10. BUILDING THE MODELS Normalized Data
Each object contributes with:
Landmark points, aligned
Shape-free patch, normalized
Statistical analysis (PCA)

11. BUILDING THE MODELS Principal Component Analysis
Objects (shapes, gray-levels) as vectors:
Distribution of s points in n- dimensional space
Alternative coordinate system: - no correlations - sorted coordinates

12. BUILDING THE MODELS Principal Component Analysis
Method: finding eigenvectors and eigenvalues of the covariance matrix
Linear model:

13. BUILDING THE MODELS Shape Model
Shape vector:
Model:

14. BUILDING THE MODELS Gray-level Model
Gray-level vector: samples of gray values
Model:

15. BUILDING THE MODELS Appearance Model
Appearance vector:
Model:

16. BUILDING THE MODELS All Faces – Modes of Variation
First mode
Second mode
Third mode

17. BUILDING THE MODELS Neutral - Appearance Variation
Changing the first three modes of variation simultaneously

18. BUILDING THE MODELS Hearts - Appearance Variation
Changing the first three modes of variation simultaneously

19. MANIPULATING FACES Reconstruction

20. MANIPULATING FACES Caricatures

21. MANIPULATING FACES Forced Smiles

22. ACTIVE APPEARANCE MODELS Concept
Search – optimization to minimize
Learning – estimating A
Iterative model refinement

23. Thank you!