  In this paper, we report an optimized union-find (UF) algorithm that can
label the connected components on a 2D image efficiently by employing the GPU
architecture. The proposed method contains three phases: UF-based local merge,
boundary analysis, and link. The coarse labeling in local merge reduces the
number atomic operations, while the boundary analysis only manages the pixels
on the boundary of each block. Evaluation results showed that the proposed
algorithm speed up the average running time by more than 1.3X.
