Face Detection And Recognization

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  • Words: 635
  • Pages: 23
- Hardik Dhokai ( 07CE017 )

Guide: Prof. Ashish Patel Computer Department LDRP Institute of Technology and Research

Outline Introduction Goal of face detection Challenges in face detection Different Techniques used for face Detection Pros and Cons of each technique Discussion and Future work

Introduction Face Detection Identify and locate human faces in an image regardless of their Size Expressions Pose Illumination Orientation and occlusion where are the faces, if any?

Cont...

Definition The face detection problem can be defined as : “Given as input an image, which could be a digitized video signal or scanned photograph, determine whether or not there are any human faces in the image if there are, return their location”.

Why Face Detection is Important? First step for most automatic security system First step in many surveillance systems Face is the unique identity of a person Example applications: Automated security systems Intelligence information

Why Face Detection is Difficult? Face Localization: A simplified detection problem with the assumption that an input image contains only one face.

Facial feature detection: To detect the presence and location of features such as eyes, nose, nostrils, eyebrow, mouth,

lips, ears, etc.

Face tracking: Continuously estimate the location and possibly the orientation of face in an image sequence in real time.

Facial expression recognition: concerns the affective states of human’s like happy,sad,disgusted etc.

Cont...

Size: small faces are more difficult to detect. pose: frontal, 45 degree, profile, upside down. Presence or absence of structural beards, moustache, and glasses.

Orientation: Faces can appear in different orientations within the image plane depending on the angle of the camera

and face.

occlusions: faces may be partially occluded by other

Some Examples of Partially Occluded Faces

Approaches to Detect faces Knowledge-based Approach 

Feature invariant Approach



Template matching Approach



Appearance-based Approach

Knowledge-Based Approach 

Represent a face using a set of human-coded rules Example: 





The center part of face has uniform intensity values A face often appears with two eyes that are symmetric to each other, a nose and a mouth

Use these rules to guide the search process

Level 2

Level 1 The input image

Candidates of faces

Level 3

Basic face

Face location&

locations

segmentation

Knowledge-based Approach: Summary: 

Pros: 

Easy to come up with simple rules



Based on the coded rules, facial features in an input image are extracted first, and face candidates are identified



Cons: 

Difficult to translate human knowledge into rules



Difficult to extend this approach to detect faces in different poses:

Feature-Based Approach 

Detect facial features (eyes, nose, mouth, etc) first



Facial features: edge, intensity, shape, texture, skin color, etc



Aim to detect invariant features



Group features into candidates and verify them

Feature-Based Approach : Summary 

Pros: 



Features are invariant to pose and orientation change

Cons: 



Difficult to locate facial features due to several corruption (illumination, occlusion) Difficult to detect features in complex background

Template Matching Approach 

Store a template Predefined: based on edges or regions



Deformable: based on outline of face



Templates are handcoded (not learned)



Use correlation to locate faces

Template-Based Approach : Summary 

Pros: 



It is simple to implement

Cons: 



Templates needs to be initialized near the face images Difficult to enumerate templates for different poses (similar to knowledgebased methods)

Appearance-Based Approach Uses machine learning algorithms. Fast and fairly robust techniques. Train a classifier using positive examples of faces Various Methods: Neural model Support vector machine (SVM) Adaboost Hidden Markov Model Distribution Method

CONCLUSION - Face detection is still in a learning mode -

- We hope that in future we will have robust Approaches/methods to detect the face

-

algorithms

Web Resources Face detection home page http://www.facedetection.com/ http://vasc.ri.cmu.edu/NNFaceDetector/#upright

http://vision.ucsd.edu/kriegman-grp/research/ptrack/index.html http://www.cvpr.org/2006/index.html

http://web.archive.org/web/20030602192115/http://www.cs.ru

References

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