Abstract: The existing region growing algorithms do not take into account the direction of the nearest neighbor relations,which results in frequent rebuilt of the neighbor relations．In this paper,a fast algorithm for remote sensing image segmentation was proposed based on nearest neighbor directed graph．First of all,a remote sensing image was segmented using the watershed algorithm,and then a nearest neighbor directed graph was established on the basis of the region objects of the previous segmentation．In the region growing phrase,the adjacent region objects were merged along the directed edges．When the first round is finished,the nearest neighbor directed graph should be rebuilt,and the second round of region growing is initiated．This process repeats until the region number is no longer changed．This method avoids recalculating the neighbor relations whenever a merge happens,which reduces the computational complexity．The experimental results show that the algorithm proposed in this paper is more reasonable,more efficient compared with the other three algorithms.

Key words: Remote sensing image segmentation,Nearest neighbor directed graph,Region growing