How to and how not to use graph cuts
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Transcript of How to and how not to use graph cuts
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How to and how not to usegraph cuts
Karen Liu and Brett Allen
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What graph cuts is good for
• Suppose you want to label the nodes in a graph:
• For each node, you have:– a data term: D(p, fp) – the cost of labeling node p with label fp– a neighbor term, V(fp, fq), the cost of labeling connected nodes p and q with labels fp and fq.
• You want to minimize:
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The algorithm
• we used an existing min-cut implementation
• for each α-expansion, we build a graph that expresses the desirability of switching each node’s label to α ( ):
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Application 1: Stripe labeling
A harder case
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Using graph cuts
color labelcolor pixel),( pfpD
otherwise1
1 if0
if0
),( qp
qp
qp ff
ff
ffV
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Results
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What went wrong?!
True labeling: … 11 12 13 14 15 16 17 18 19 …
Current labeling: … 11 12 13 1 2 3 17 18 19 …
…any α-expansion will not improve the energy!
α-expansion only works if:
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Application 2: Stereo
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Using graph cuts
)by shiftedcolor pixelright (color pixelleft ),( pp fwfpD
otherwise1
if0
),(qp
qp
ff
ffV
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Results
Graph cuts Ground truth
Parameters: 12 labels (12-34 pixel displacement), w = 10
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Results
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Results (2)
Input
Graph cuts Ground truth
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Results (3)