In light of the developing process, four semantic image annotation methods text-based manual image annotation, automatic image annotation, Web image annotation with associated texts and folksonomy are reviewed in this paper. Then this paper points out that the existing semantic image annotation methods are faced with the problem of semantic gap, analyzes the root of semantic gap, and introduces beneficial attempts in solving this problem. Furthermore, with the analysis of development venation and discipline distribution of the research of semantic image annota...
