How to and how not to use graph cuts

1. How to and how not to usegraph cuts Karen Liu and Brett Allen

2. You want to minimize: 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.

3. 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 ( ):

4. Application 1: Stripe labeling A harder case

5. Using graph cuts

6. Results

7. 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:

8. Application 2: Stereo

9. Using graph cuts

10. Results Ground truth Graph cuts Parameters: 12 labels (12-34 pixel displacement), w = 10

11. Results

12. Results (2) Input Ground truth Graph cuts

13. Results (3)