Active Contours

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Active Contours
In the Name of Allah

• To be presented in Machine Vision Course by
• Neda Shahidi
• N_shahidi_at_ce.sharif.edu
• Instructor
• Dr. Jamzad
• Computer Dept. Sharif Unicersity of Technology
• Spring 2006

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Outline

• Active contours in simple forms
• Simulation results
• Active contours in advance forms
• Drawbacks of gradient based methods
• Level set formulation
• Simulation Results

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What is a Contour

• Ordered collection of points
• Lock onto features of interest like edges, lines
  and object boundaries

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Active Contour Method Energy function

• Energy function for each point vi of contour
• Internal energy Shape of the contour
• External energy Image properties

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Active Contour Internal Energy

• Internal energy
• Continuity energy
• Line
• Circle
• Balloon force

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Active Contour External Energy

• External energy
• Image intensity energy
• Image gradient energy

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Simulation Results

• Dependency to initial Guess
• Contribution of gradient direction
• Contribution of balloon force

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Advance Form (Gradient Based)

• Contour
• Defining Edge Function
• F function evolution
• Goal Minimizing F(F(t,x,y))

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Level Set Formulation

• Simple case

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Level Set Formulation
H is Heaviside Function

• Goal

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Level Set Formulation
Euler_Lagrange equation for ?
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Simulation Results
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Simulation Results
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References

• Tony F. Chan and Luminita A. Vese, Active
  Contours Without Edges, IEEE TRANSACTIONS ON
  IMAGE PROCESSING, VOL. 10, NO. 2, FEBRUARY 2001,
  pp. 266-277.
• Blair Mackiewich, Intracranial Boundary Detection
  and Radio Frequency Correction in Magnetic
  Resonance Images, M.Sc. thesis, Simon Fraser
  University, August 1995.

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• Thanks
• This presentation is available at
• ce.sharif.edu/n_shahidi