thinning & distance field
DESCRIPTION
Thinning & Distance Field. Advisor : Ku-Yaw Chang Speaker : Jhen -Yu Yang. Outline. Introduction Method Method 1 Method 2 Reference. Introduction. Thinning To produce a skeleton Iteratively removing voxels from the boundary. Introduction. Distance field Find ridge points - PowerPoint PPT PresentationTRANSCRIPT
Thinning & Distance Field
Advisor:Ku-Yaw Chang
Speaker: Jhen-Yu Yang
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Outline Introduction Method
Method 1 Method 2
Reference
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Introduction Thinning
To produce a skeleton Iteratively removing voxels from the boundary
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Introduction Distance field
Find ridge points Connect them
Polyp
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Outline Introduction Method
Method 1 Method 2
Reference
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Method 1 Use two-subfield thinning algorithm
Extracting medial curves on 3D images Source : [C.-M. Ma et al., 2002]
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An original object and its skeleton.
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In a 3D binary image Voxels are partitioned into two subsets
C (object voxel) Marked by
C’ (background voxel) Marked by
A voxel marked Don’t care Can match either C or C’
Method 1
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Method 1 Use the Templates (or masks)
To test each boundary voxel Remove the simple point
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Tested voxels
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Let x be a C-voxel Simple point
Only one C-component in N*(x) x is adjacent to only one C-component
Method 1
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C-component = { a1, d1, b1, e1, δ(x) };
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Voxel x is U-deletable With a C-neighbor β(x)
Method 1
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x can be deleted
( 1 )
( 2 )
( 3 )
C-component = { a, b, c, β(x) };
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Method 1
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Voxels are partitioned into two subfields Two directly adjacent voxels
In different subfields Two diagonally adjacent voxels
In same subfield
Directly adjacent
Diagonally adjacent
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Branches
Method 1
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A tree structure object and its skeleton.
A letter ‘A’ and its skeleton.
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Outline Introduction Method
Method 1 Method 2
Reference
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Method 2 Using a distance field
Compute an object’s centerline Source : [I. Bitter et al., 2001]
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Colon and its skeleton. Dinosaur and its skeleton.
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Method 2 Compute the distance
Each inside voxel to the boundary Recorded at each voxel
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(1)
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Method 2
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Another DT case
Source Result
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Compute gradient vector For each voxel position Requires reading of
neighboring voxels
Method 2
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Vector and its arrow
(2)
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Six classes of regions Flag non-uniform gradient vectors
Directions are non-uniform
Method 2
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(3)GVF: Gradient Vector Field
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Method 2 Connect flagged voxels
Pick a flagged voxel and flag the corresponding voxel Start and traverse Stop when another flagged voxel is reached
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(4)
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Method 2
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Results
Lobster and its skeleton. Aorta and its skeleton.
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Outline Introduction Method
Method 1 Method 2
Reference
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Reference Cherng-Min Ma, Shu-Yen Wan. A medial-surface oriented 3-d two-subfield
thinning algorithm. Pattern Recognition Letters 22 (2001) 1439-1446 Cherng-Min Ma, Shu-Yen Wan, Her-Kun Chang. Extracting medial curves on
3D images. Pattern Recognition Letters 23 (2002) 895-904 Ingmar Bitter, Arie E. Kaufman, Mie Sato.Penalized-Distance Volumetric
Skeleton Algorithm.IEEE Transaction On Visualization And Computer Graphics, Vol. 7, No. 3, July-September 2001
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The endThanks.
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