genetic algorithms and image understanding sam clanton computer integrated surgery ii march 14, 2001
TRANSCRIPT
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Genetic Algorithmsand Image Understanding
Sam Clanton
Computer Integrated Surgery II
March 14, 2001
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Resources
• Bhanu, Bir and Lee, Sunkee. Genetic Learning for Adaptive Image Segmentation. Kluwer Academic Publishers, 1994
• Goldberg, David. Genetic Algorithms in Search, Optimization, and Machine Learning. Addison Wesley Longman, 1989.
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Genetic Algorithms
• Optimization Problems
• Adaptive Systems
• Speed-Critical Applications
Are Useful For…
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General Problem to be Solved
• The k-armed bandit problem
Picture: Goldberg
How do we maximize our winnings?
GA’s are good for multiple, many-armed bandits.
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What Is a Genetic Algorithm?
• Operates on principle of
survival of the fittest
• “Population Pool” of Parameters
• Genetic Operators - Reproduction, Crossover, and Mutation
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Survival Of the Fittest
• Analogous to survival in biological system
• Fitness Function
• Optimization == Finding most fit parameter set for a particular problem
Selk(an elk) ~ Ability to run away (elk, lions, tigers)Ability to run away (herd, lions, tigers)
Spset(a pset) ~ Ability to perform task(pset, input)Ability to perform task(population, input)
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Population Pool
24, 32, 76, 1
34, 43, 6, 17
• “Surviving” parameter sets are kept around
• Individuals are extracted and applied when input resembles past input for that individual.
• Genetic operators add new individuals to pool
• Individuals can be dropped when they appear useless
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Genetic Operators
• Affect survival of particular schema
Schema - string representation of a feature
• Reproduction f(H) / favg
• Crossover 1 - pc * L(H) / L(total)• Mutation 1 - L(H) * pm
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Feature Preservation
• Overall Equation
m(H, t+1) = m(H, t) * F(H)/favg
Reproduction
* (1 - pc L(H) / L(tot)
Crossover
- L(H) * pm )
Mutation
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An Example - Reproduction
String Initial Pop
X val F(x) = x * x
Pselect (fitness/ total fitness)
Exp. Count
(fitness / avg fitness)
Actual Count (roulette)
1 01101 13 169 .14 .58 1
2 11000 24 576 .49 1.97 2
3 01000 8 64 .06 .22 0
4 10011 19 361 .31 1.23 1
Sum 1170
Avg 293
Max 576
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An Example - CrossoverString Pop. Pool
(w/
Crossover)
Mate Crossover Site
New Pop. Pool
X value F(x)
1 0110|1 2 4 01100 12 144
2 01100|0 1 4 11001 25 625
3 11|000 4 2 11011 27 729
4 10|011 3 2 10000 16 256
Sum 1754
Avg 439
Max 739
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GA’s in Image Segmentation
• Optimization problem
• “Twiddling Knobs” Approach
• Relationship to “Many k-armed bandit” problem
Figure: Bhanu, Lee
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GA method for image segmentation
Figure: Bhanu, Lee
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Images differ in characteristics such as brightness, saturation, skewness, entropy, etc.
Use these values as inputs to genetic algorithm
Figure: Bhanu, Lee
Image Analysis
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Evolution of Segmentation System
Figure: Bhanu, Lee
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The project: Implementation in DSP / FPGA
Image Capture
Image Processor
Geneticoptimizer
Collator
Memory
Output
Edge DetectorsFPGA
DSP