Stephan Tschechne Chair for Image Understanding Computer Science Technische Universität München [email protected] Designing vs. Learning the Objective Function for Face Model Fitting Abschlußvortrag Diplomarbeit
Jan 20, 2018
Stephan Tschechne
Chair for Image UnderstandingComputer Science
Technische Universität München
Designing vs. Learning the Objective Function for Face Model Fitting
Abschlußvortrag Diplomarbeit
28.6.06 2/15Technische Universität MünchenStephan Tschechne
• Model-based Image Understanding
• Face Model Fitting
• Objective Functions
• Experimental Results
Overview:
28.6.06 3/15Technische Universität MünchenStephan Tschechne
Understanding Facial Images Various Applications
Identification Mimics Hands-free Control
Image Database: 850 Natural Images
28.6.06 4/15Technische Universität MünchenStephan Tschechne
Deformable Face Model 134 Contour Points Perform PCA Point Distribution Model
Description of an Instance: Parameter Vector p = (x,y,scaling,rotation,deform1..deform17)
28.6.06 5/15Technische Universität MünchenStephan Tschechne
Objective Function• Fitting Algorithms Search for Correct p:
Optimisation Problem• Objective Function Calculates Fitting Accuracy • Lowest Value for Correct Solution
F(Img,p1)=0.0 F(Img,p2)=0.3 F(Img,p3)=0.6
28.6.06 6/15Technische Universität MünchenStephan Tschechne
RequirementsFormulation of Requirements for Robust Objective Functions:
R1: Correct Position of MinimumR2: One MinimumR3: Continuous BehaviourR4: Gradient Vectors Point Away
Optimal Objective Functions:
28.6.06 7/15Technische Universität MünchenStephan Tschechne
Traditional Objective FunctionsCalculation of Objective Function Value ?• Intuitive approach:
Manual Selection of Salient Features:• Distance to Edges..
28.6.06 8/15Technische Universität MünchenStephan Tschechne
Traditional Objective Functions
• …or Distance to Edges from Skin Colour Images
28.6.06 9/15Technische Universität MünchenStephan Tschechne
Traditional Approach Problem: Desired Edges are not the Strongest Ones
28.6.06 10/15Technische Universität MünchenStephan Tschechne
Contribution
Robust Objective Function Better Fulfillment of the Requirements
?!
28.6.06 11/15Technische Universität MünchenStephan Tschechne
Learning the Robust Objective Function Training data:
Ground Truth from Image Database Haar-like Features Desired Value from
Optimal Objective Function
Machine Learns Rules with Model Trees
28.6.06 12/15Technische Universität MünchenStephan Tschechne
Training Data: Feature Values Fi Result R Deliberately Move Instance to Gather Values
Model Trees Learn: F(Feature Values) Result
F1=134F2=66 … R=0.7
F1=54F2=234 … R=0.0
F1=281F2=11 … R=0.5
28.6.06 13/15Technische Universität MünchenStephan Tschechne
Experimental ResultsCenter: Correct ParametersAxes: Variation of p towards ….
..translation ..deformation
28.6.06 14/15Technische Universität MünchenStephan Tschechne
Challenges:
Image Database with Natural Images Database High Dimensionality of Parameter Vector Verification of Requirements
Future research: Model Tracking Other Models: 3D, Appearance Models.. Different Features Other Positions for Features
28.6.06 15/15Technische Universität MünchenStephan Tschechne
The End.
Any Questions ?