Transcript Active Shape and Appearance Models A 4-WEEK PROJECT IN by Renée Anderson

A 4-WEEK PROJECT IN
Active Shape and
Appearance Models
by Renée Anderson
and Vedrana Andersen
Overview




Preprocessing (Renée)
Building models (Vedrana)
Manipulating faces (Renée)
Active appearance models (Vedrana)
STATISTICAL MODELS
Concept
Several steps developed by Cootes and
Taylor:



Data capture and representation
Data normalization
Statistical analysis
PREPROCESSING
Data
For each object
(face, heart, spine):
 Image
 Landmark points
PREPROCESSING
Cropping and Translation


Cropping out the
background
Center of gravity of
landmark points in
the center of
image
PREPROCESSING
Alignment


Allowed
transformations:
translation,
rotation and
scaling
Iterative method:
aligning each
shape with mean
shape
PREPROCESSING
Masking


For visualization
Leave inside of
convex hull of
landmark points
PREPROCESSING
Warping


Mapping landmark
points to mean
shape
Tried two
- piecewise linear
- thin-plate spline
PREPROCESSING
Gray-level Normalization


Applying scaling
and offset to graylevel vectors
(samples)
Iterative method:
normalizing each
gray-level vector
with mean graylevel
BUILDING THE MODELS
Normalized Data
Each object contributes with:
 Landmark points, aligned
 Shape-free patch, normalized
Statistical analysis (PCA)
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
BUILDING THE MODELS
Principal Component Analysis


Method: finding eigenvectors and
eigenvalues of the covariance matrix
Linear model:
BUILDING THE MODELS
Shape Model

Shape vector:

Model:
BUILDING THE MODELS
Gray-level Model


Gray-level vector:
samples of gray
values
Model:
BUILDING THE MODELS
Appearance Model

Appearance vector:

Model:
BUILDING THE MODELS
All Faces – Modes of Variation
First mode
Second mode
Third mode
BUILDING THE MODELS
Neutral - Appearance Variation

Changing the first
three modes of
variation
simultaneously
BUILDING THE MODELS
Hearts - Appearance Variation

Changing the first
three modes of
variation
simultaneously
MANIPULATING FACES
Reconstruction
MANIPULATING FACES
Caricatures
MANIPULATING FACES
Forced Smiles
ACTIVE APPEARANCE MODELS
Concept

Search – optimization to minimize

Learning – estimating A

Iterative model refinement
Thank you!