Fill gaps between regions or split overlapping regions.

expand_region closes gaps between the input regions, which resulted from the suppression of small regions in a segmentation operator, for example, (mode 'image'), or to separate overlapping regions (mode 'region'). Both uses result from the expansion of regions. The operator works by adding or removing a one pixel wide ``strip'' to a region.

The expansion takes place only in regions, which are designated as not ``forbidden'' (parameter ForbiddenArea). The number of iterations is determined by the parameter Iterations. By passing 'maximal', expand_region iterates until convergence, i.e., until no more changes occur. By passing 0 for this parameter, all non-overlapping regions are returned. The two modes of operation ('image' and 'region') are different in the following ways:

  'image'
          The input regions are expanded iteratively until they
          touch another region or the image border.  Because
          expand_region processes all regions simultaneously, gaps between
          regions are distributed evenly to all regions.
          Overlapping regions are split by distributing the area of
          overlap evenly to both regions.

  'region'
          No expansion of the input regions is performed.  Instead,
          only overlapping regions are split by distributing the
          area of overlap evenly to the respective regions.  Because
          the intersection with the original region is computed
          after the shrinking operation gaps in the output regions
          may result, i.e., the segmentation is not complete.  This
          can be prevented by calling expand_region a second time with the
          complement of the original regions as ``forbidden area.''

read_image(Image,'fabrik')
threshold(Image,Light,100,255)
disp_region(Light,WindowHandle)
connection(Light,Seg)
expand_region(Seg,[],Exp1,'maximal','image')
set_colored(WindowHandle,12)
set_draw(WindowHandle,'margin')
disp_region(Exp1,WindowHandle)

expand_region always returns the value 2 (H_MSG_TRUE). The behavior in case of empty input (no regions given) can be set via set_system('no_object_result',<Result>), the behavior in case of an empty input region via set_system('empty_region_result',<Result>), and the behavior in case of an empty result region via set_system('store_empty_region',<true/false>). If necessary, an exception handling is raised.

expand_region is reentrant and processed without parallelization.

pouring, threshold, dyn_threshold, regiongrowing

dilation1

expand_gray, interjacent, skeleton

Region processing