A high-speed run-based two-scan labeling algorithm

Abstract

This paper presents a run-based two-scan algorithm for labeling connected components in a binary image. Unlike conventional two-scan labeling algorithms which resolve label equivalences by processing pixels one by one, our algorithm resolves label equivalences by processing runs one by one. At any time, all provisional labels that are assigned to a connected component are combined in a set, and the smallest label is used as their representative label. The corresponding relation of a provisional label and its representative label are recorded in a table. Whenever different components are found to be connected, all provisional label sets related to these connected components are merged together, and the smallest provisional label is considered to be the representative label. When the first scan is finished, all provisional labels that were assigned to each connected component in the given image will have a unique representative label. During the second scan, we need only to replace each provisional label with its representative label. Experimental results on various types of images demonstrated that our algorithm outperforms all conventional labeling algorithms.