Post on 31-Dec-2015
description
transcript
A medial-surface oriented 3-d two-subfield
thinning algorithm
Author: Cherng-Min Ma, Shu-Yen WanSource: Pattern Recognition Letters 22 (2001) 1439-1446 Speaker: Jhen-Yu YangAdvisor: Ku-Yaw Chang
Introduction• Thinning
– A fundamental preprocess– To remove unnecessary information
• Allow to topological analysis
2011/12/6
Introduction• 2-subfield thinning algorithm
– Voxels are classified• 6- or directly adjacent voxels
– Different subfields
• Diagonally adjacent voxels– Same subfields
– Applied to voxels in each subfield alternatively
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Method• Basic notations
– Two kinds of voxels• 0’s and 1’s
– N(x)– N*(x) = N(x) – {x}– e(x)– layer
• Ex: east layer– middle layer
• Ex: midEW layer
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Method• Basic notations
– Two kinds of voxels• 0’s and 1’s
– N(x)– N*(x) = N(x) – {x}– e(x)– layer
• Ex: east layer– middle layer
• Ex: midEW layer
2011/12/6
Method• Condition 1, an upper border 1, x, with l(x) = 1 is:
– U-deletable• adjacent to only one 1’s in the midEW layer and
midNS layer, and• a, is 1, then b=1 or c=1
– U-preserving• See next page
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[vertically deletable or preserving]
Method(Condition 1, cont.)
• Condition 1– U-preserving, if x is U-deletable, and
• l(x), adjacent to two distinct 1-component • in N*(x) or• l(x), adjacent only two 1’s, p and q in N*(x) • where {x, l(x), p, q}• is a 2-d element
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Method• Condition 2, an end 1, x, δ(x)=lw(x)=1 in midNS layer is:
– UE-deletable• if all voxels are 0’s, upper and east layer
– UE-preserving• See next page
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Method(Condition 2, cont.)
• Condition 2, UE-preserving, if x is UE-deletable, and
– (a) a1 = a2 = b1 = b2=0, and either a0 = a3 =1 or b0 = b3 =1 ; or
– (b) a0=a3=p=0, where p= a1 or a2, or b0=b3=q=0, where q =b1 or b2
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