Unformatted text preview: e region in an upper pyramid level.
The segmentation process can be understood as the construction of a segmentation quadtree
where each leaf node represents a homogeneous region. Splitting and merging corresponds to Faculty of Engineering Robotics Technology MECH 4041 21
B.Eng (Hons.) Mechatronics S. Venkannah Mechanical and Production Engineering Department removing or building parts of the segmentation quadtree. Split-and-merge methods usually store
the adjacency information in region adjacency graphs (or similar data structures). Using
segmentation trees, in which regions do not have to be contiguous, is both implementationally
and computationally easier.
An unpleasant drawback of segmentation quadtrees is the square region shape assumption
merging of regions which are not part of the same branch of the segmentation tree
Because both split-and-merge processing options are available, the starting segmentation does
not have to satisfy any of the homogeneity conditions.
May be summarized by the following procedure:
1. split into four disjointed quadrants any region Ri where P(Ri) = FALSE;
2. merge any adjacent regions Rj and Rk for which P(Rj U Rk) = TRUE; and
3. stop when no further merging or splitting is possible
Several variations of this basic approach are possible, e.g. one possibility is to split the image
initially into a set of square blocks. Further splitting is carried out as described, but merging is
initially limited to groups of four blocks that are descendants in the quad tree representation and
that satisfy the predicate P. When no further mergings of this type are possible, the procedure is
terminated by one final merging of regions satisfying step 2. At this point, the merged regions
may be of different sizes. The principal advantage of this approach is that it uses the same
quadtree for splitting and merging, until the final merging step.
Summary Region-based Segmentation Region growing segmentation should satisfy the following condition of comple...
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