1. A computer-implemented method, comprising: obtaining a region of uncertainty in an image within which a global labeling solution for the image lies; covering the region of uncertainty with a set of multiple overlapping tiles; applying a labeling function to each tile in a first subset of the tiles to generate a local labeling for each of the tiles in the first subset; and applying the labeling function to each tile in a second subset of the tiles to generate a local labeling for each of the tiles in the second subset, wherein the local labeling for a tile in the first subset is input as a boundary condition to the labeling function when applied to a tile in the second subset that overlaps the tile in the first subset; and merging the local labelings for all of the tiles in all of the subsets to form a global labeling for the image.