A 4-WEEK PROJECT IN Active Shape and Appearance Models

1
A 4-WEEK PROJECT INActive Shape and Appearance
Models

• by Renée Anderson
• and Vedrana Andersen

2
Overview

• Preprocessing (Renée)
• Building models (Vedrana)
• Manipulating faces (Renée)
• Active appearance models (Vedrana)

3
STATISTICAL MODELS Concept

• Several steps developed by Cootes and Taylor

• Data capture and representation
• Data normalization
• Statistical analysis

4
PREPROCESSINGData
For each object (face, heart, spine)

• Image
• Landmark points

5
PREPROCESSINGCropping and Translation

• Cropping out the background
• Center of gravity of landmark points in the
  center of image

6
PREPROCESSINGAlignment

• Allowed transformations translation, rotation
  and scaling
• Iterative method aligning each shape with mean
  shape

7
PREPROCESSINGMasking

• For visualization
• Leave inside of convex hull of landmark points

8
PREPROCESSINGWarping

• Mapping landmark points to mean shape
• Tried two- piecewise linear- thin-plate spline

9
PREPROCESSINGGray-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 MODELSNormalized Data

• Each object contributes with
• Landmark points, aligned
• Shape-free patch, normalized
• Statistical analysis (PCA)

11
BUILDING THE MODELSPrincipal 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 MODELSPrincipal Component Analysis

• Method finding eigenvectors and eigenvalues of
  the covariance matrix
• Linear model

13
BUILDING THE MODELSShape Model

• Shape vector
• Model

14
BUILDING THE MODELSGray-level Model

• Gray-level vector samples of gray values
• Model

15
BUILDING THE MODELSAppearance Model

• Appearance vector
• Model

16
BUILDING THE MODELSAll Faces Modes of Variation
First mode
Third mode
Second mode
17
BUILDING THE MODELSNeutral - Appearance Variation

• Changing the first three modes of variation
  simultaneously

18
BUILDING THE MODELSHearts - Appearance Variation

• Changing the first three modes of variation
  simultaneously

19
MANIPULATING FACESReconstruction
20
MANIPULATING FACESCaricatures
21
MANIPULATING FACESForced Smiles
22
ACTIVE APPEARANCE MODELSConcept

• Search optimization to minimize
• Learning estimating A
• Iterative model refinement

23
Thank you!