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