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Connected operators based on region-trees

Connected operators are operators that act by merging of elementary regions called flat zones. They cannot create new contours nor modify their position. Therefore, they have very good contour preservation properties. This paper discusses connected operators based on region trees. The filtering approach involves three steps: first, a region tree representation of the input image is constructed. Second, the simplification is obtained by pruning the tree and third, the output image is constructed from the pruned tree. The paper focuses on the trees used in practice and discusses various pruning strategies used in practice.