difference

Herror ::difference ( Hobject Region, Hobject Sub, Hobject *RegionDifference ) HRegion HRegion::Difference ( const HRegionArray &Sub ) const HRegionArray HRegionArray::Difference ( const HRegionArray &Sub ) const

Calculate the difference of two regions.

::difference calculates the set-theoretic difference of two regions:

   (Regions in Region) - (Regions in Sub)

The resulting region is defined as the input region (Region) with all points from Sub removed. The following two special regions can also be used as input:

     'full'    i.e., the full region (FULL_REGION in Halcon/C) or
     'empty'   i.e., the empty region (EMPTY_REGION in Halcon/C).

Attention

Empty regions are valid for both parameters. On output, empty regions may result The value of the system flag 'store_empty_region' determines the behavior in this case.

Parameters

`Region` (input_object)	region(-array) `->` Hobject: HRegion(Array)
Regions to be processed.

`Sub` (input_object)	region(-array) `->` Hobject: HRegion(Array)
The union of these regions is subtracted from Region.

`RegionDifference` (output_object)	region(-array) `->` Hobject : HRegion(Array)*
Resulting region.

Example

/* provides the region X without the points in Y */
difference(X,Y,&RegionDifference);
/* provides the region. */
difference(Region,EMPTY_REGION,&RegionDifference);

Complexity

Let N be the number of regions, F_{1} be their average area, and F_{2} be the total area of all regions in Sub. Then the runtime complexity is O(F_{1} * F_{1}) + N * (F_{1} + F_{2})).

Result

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

Possible Predecessors

::threshold, ::connection, ::regiongrowing, ::pouring, ::class_ndim_norm

Possible Successors

::select_shape, ::disp_region

Module

Region processing