In this paper

a new method for detecting specific objects in the image is presented. It consists of three steps. Firstly

a watershed transformation (WT) is used for over segmenting the image in different small basins and dams. The desired object should be one of these basins or the combination of some ones. Secondly

the basins which are most impossible to be the objects are deleted

and then the neighboring relationships between the remainders are analyzed to construct a region adjacency graph (RAG). Finally

an energy function is constructed and a heuristic genetic algorithm (GA) is proposed to extract the optimized sub graphs from the RAG. The regions corresponding to the sub graphs are the desired objects. Experiment results demonstrate the feasibility of this approach.