Erode a region with a circular structuring element.

erosion_circle applies a Minkowski subtraction with a circular structuring element to the input regions Region. Because the circular mask is symmetrical, this is identical to an erosion. The size of the circle used as structuring element is determined by Radius.

The operator results in reduced regions, smoothed region boundaries, and the regions smaller than the circular mask are eliminated. It is useful to select only values like 3.5, 5.5, etc. for Radius in order to avoid a translation of a region, because integer radii result in a circle having a non-integer center of gravity which is rounded to the next integer.

#include "HIOStream.h"
#if !defined(USE_IOSTREAM_H)
using namespace std;
#endif
#include "HalconCpp.h"

main()
{
  cout << "Simulation of 'erosion_circle ()'" << endl;
  cout << "First = original image " << endl;
  cout << "Red   = after segmentation " << endl;
  cout << "Blue  = after erosion " << endl;

  HByteImage img("monkey");
  HWindow    w;

  HRegion      circ   = HRegion::GenCircle (10, 10, 1.5);
  HRegionArray regs   = (img >= 128).Connection();
  HRegionArray minsub = regs.MinkowskiSub1 (circ, 1);

                         img.Display (w);      w.Click ();
  w.SetColor ("red");   regs.Display (w);     w.Click ();
  w.SetColor ("blue");  minsub.Display (w);   w.Click ();

  return(0);
}

Let F1 be the area of an input region. Then the runtime complexity for one region is:

       O(2 * Radius * sqrt(F1)) .

erosion_circle returns 2 (H_MSG_TRUE) if all parameters are correct. The behavior in case of empty or no input region can be set via:

  a) no region:    set_system('no_object_result',<RegionResult>)
  b) empty region: set_system('empty_region_result',<RegionResult>)

erosion_circle is reentrant and automatically parallelized (on tuple level).

threshold, regiongrowing, watersheds, class_ndim_norm

connection, reduce_domain, select_shape, area_center

minkowski_sub1

gen_circle, dilation_circle, closing_circle, opening_circle

Foundation