expand_region — 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 that are designated as
not “forbidden” (parameter
ForbiddenArea). The number
of iterations is determined by the parameter
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:
The input regions are expanded iteratively until they
touch another region or the image border.
In this case, the image border is defined to be the
rectangle ranging from (0,0) to (row_max,col_max).
Here, (row_max,col_max) corresponds to the lower right
corner of the smallest surrounding rectangle of all input regions
(i.e., of all regions that are passed in
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.
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
Regions for which the gaps are to be closed, or which are to be separated.
Regions in which no expansion takes place.
Expanded or separated regions.
→(integer / string)
Number of iterations.
Default value: 'maximal'
Suggested values: 'maximal', 0, 1, 2, 3, 5, 7, 10, 15, 20, 30, 50, 70, 100, 200
Typical range of values:
Minimum increment: 1
Recommended increment: 1
Default value: 'image'
List of values: 'image', 'region'
read_image(Image,'clip') threshold(Image,Dark,0,150) connection(Dark,ConnectedRegions) gen_circle (Circle, 400, 400, 200.5) expand_region (ConnectedRegions, Circle, RegionExpanded, 'maximal', 'image') dev_display (RegionExpanded)
expand_region always returns the value 2 (H_MSG_TRUE). The behavior in
case of empty input (no regions given) can be set via
the behavior in case of an empty input region via
and the behavior in case of an empty result region via
If necessary, an exception is raised.