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 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:
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 Regions and ForbiddenArea). 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.
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.”
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.
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: 0 ≤ Iterations ≤ 1000 (lin)
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 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 is raised.
pouring, threshold, dyn_threshold, regiongrowing
expand_gray, interjacent, skeleton