ee4328, section 005 introduction to digital image processing image segmentation zhou wang dept. of...
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EE4328, Section 005 Introduction to Digital Image
Processing
Image Segmentation
Zhou Wang
Dept. of Electrical EngineeringThe Univ. of Texas at Arlington
Fall 2006
• What is Image Segmentation?
• Image Segmentation Methods– Thresholding– Boundary-based– Region-based: region growing, splitting and merging
Concepts and Approaches
Partition an image into regions, each associated with an object but what defines an
object?
From Prof. Xin
Li
Thresholding Method
0 50 100 150 200 2500
0.5
1
1.5
2
2.5
3x 10
4
thresholding
histogram From Prof. Xin Li
single threshold
multiple thresholds
From [Gonzalez & Woods]
Thresholding Method
From [Gonzalez & Woods]
• Global Thresholding: When does It Work?
Thresholding Method
• Global Thresholding: When does It NOT Work?– A meaningful global threshold may not exist– Image-dependent
globalthresholding
From [Gonzalez & Woods]
Thresholding Method
4
4
4
4
5
5
4
4
4
10
5
5
10 11 5
3
3
9
9
9
1 1 2 2 3
1 1 2 2 8
1 1 2 7 8
1 1 6 7 8
1 5 6 7 8
10
11
11
10
5
5
4 11 5
10 11 5
9
3
3
91 5 6 7 8
1 5 6 7 3
1 5 6 2 3
1 5 2 2 3
5
5
5
5
5
5
5
5
5
4 4 531 1 2 2 3 5
0
0
0
0
1
1
0
0
0
1
1
1
1 1 1
0
0
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1
1
0 0 0 0 0
0 0 0 0 1
0 0 0 1 1
0 0 1 1 1
0 1 1 1 1
1
1
1
1
1
1
0 1 1
1 1 1
1
0
0
10 1 1 1 1
0 1 1 1 0
0 1 1 0 0
0 1 0 0 0
1
1
1
1
1
1
1
1
1
0 0 100 0 0 0 0 1
0
0
0
0
0
0
0
0
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1
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1 1 0
0
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1
1
0 0 0 0 0
0 0 0 0 1
0 0 0 1 1
0 0 1 1 1
0 0 1 1 1
1
1
1
1
0
0
0 1 0
1 1 0
1
0
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10 0 1 1 1
0 0 1 1 0
0 0 1 0 0
0 0 0 0 0
0
0
0
0
0
0
0
0
0
0 0 000 0 0 0 0 0
Thresholding T = 4.5
Thresholding T = 5.5
true object boundary
Thresholding Method
1 1 2 2 3
1 1 2 2 8
1 1 2 7 8
1 1 6 7 8
1 5 6 7 8
4
4
4
4
5
5
4
4
4
10
5
5
10 11 5
3
3
9
9
9
5
5
5
5
5
1 5 6 7 8
1 5 6 7 3
1 5 6 2 3
1 5 2 2 3
1 1 2 2 3
10
11
11
10
5
5
4 11 5
10 11 5
9
3
3
9
5
5
5
5
4 4 53 5
4
4
4
4
5
5
4
4
4
10
5
5
10 11 5
3
3
9
9
9
1 1 2 2 3
1 1 2 2 8
1 1 2 7 8
1 1 6 7 8
1 5 6 7 8
10
11
11
10
5
5
4 11 5
10 11 5
9
3
3
91 5 6 7 8
1 5 6 7 3
1 5 6 2 3
1 5 2 2 3
5
5
5
5
5
5
5
5
5
4 4 531 1 2 2 3 5
Split
• Solution– Spatially adaptive thresholding– Localized processing
Thresholding Method
1 1 2 2 3
1 1 2 2 8
1 1 2 7 8
1 1 6 7 8
1 5 6 7 8
4
4
4
4
5
5
4
4
4
10
5
5
10 11 5
3
3
9
9
9
5
5
5
5
5
1 5 6 7 8
1 5 6 7 3
1 5 6 2 3
1 5 2 2 3
1 1 2 2 3
10
11
11
10
5
5
4 11 5
10 11 5
9
3
3
9
5
5
5
5
4 4 53 5
0 0 0 0 0
0 0 0 0 1
0 0 0 1 1
0 0 1 1 1
0 1 1 1 1
0
0
0
0
0
0
0
0
0
1
0
0
1 1 0
0
0
1
1
1
0
0
0
0
0
0 1 1 1 1
0 1 1 1 0
0 1 1 0 0
0 1 0 0 0
0 0 0 0 0
1
1
1
1
0
0
0 1 0
1 1 0
1
0
0
1
0
0
0
0
0 0 00 0
Thresholding T = 4
Thresholding T = 7
Thresholding T = 4
Thresholding T = 7
spatially adaptive threshold selection
Thresholding Method
0
0
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1
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1 1 0
0
0
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1
0 0 0 0 0
0 0 0 0 1
0 0 0 1 1
0 0 1 1 1
0 1 1 1 1
1
1
1
1
0
0
0 1 0
1 1 0
1
0
0
10 1 1 1 1
0 1 1 1 0
0 1 1 0 0
0 1 0 0 0
0
0
0
0
0
0
0
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0 0 000 0 0 0 0 0
0 0 0 0 0
0 0 0 0 1
0 0 0 1 1
0 0 1 1 1
0 1 1 1 1
0
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0
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1 1 0
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0
merge merge
merge merge
merge local segmentation results
0 1 1 1 1
0 1 1 1 0
0 1 1 0 0
0 1 0 0 0
0 0 0 0 0
1
1
1
1
0
0
0 1 0
1 1 0
1
0
0
1
0
0
0
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0 0 00 0
edgedetection
boundary detection
classificationand labeling
image segmentation
From Prof. Xin Li
Boundary-Based Method
Boundary-Based Method
From Prof. Xin Li
• Advanced Method: Active Contour (Snake) Model– Iteratively update contour (region boundary)– Partial differential equation (PDE) based optimization
Region-Based Method: Region Growing
From [Gonzalez & Woods]
Key: similarit
y measur
e
• Region Growing– Start from a seed, and let it grow (include similar neighborhood)
Region-Based Method: Split and Merge
• Split and Merge– Iteratively split (non-similar region) and merge (similar regions)– Example: quadtree approach
From [Gonzalez & Woods]
Region-Based Method: Split and Merge
original image 4 regions 4 regions(nothing to
merge)
split merge
• Example: Quadtree Split and Merge Procedure
Iteration 1
Split Step split every non-uniform region to 4Merge Step merge all uniform adjacent regions
Region-Based Method: Split and Merge
from Iteration 1 13 regions 4 regions
split merge
• Example: Quadtree Split and Merge Procedure
Iteration 2
Split Step split every non-uniform region to 4Merge Step merge all uniform adjacent regions
Region-Based Method: Split and Merge
from Iteration 2 10 regions
split merge
• Example: Quadtree Split and Merge Procedure
Iteration 3
final segmentation
result
2 regions
Split Step split every non-uniform region to 4Merge Step merge all uniform adjacent regions
Hard Problem: Textures
Similarity measure makes the difference
From Prof. Xin Li