Operators

# erosion_circle (Operator)

## Name

erosion_circle — Erode a region with a circular structuring element.

## Signature

erosion_circle(Region : RegionErosion : Radius : )

## Description

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.

## Parallelization

• Multithreading type: reentrant (runs in parallel with non-exclusive operators).
• Automatically parallelized on tuple level.

## Parameters

Region (input_object)  region(-array) object

Regions to be eroded.

RegionErosion (output_object)  region(-array) object

Eroded regions.

Radius (input_control)  real (real / integer)

Radius of the circular structuring element.

Default value: 3.5

Suggested values: 1.5, 2.5, 3.5, 4.5, 5.5, 7.5, 9.5, 12.5, 15.5, 19.5, 25.5, 33.5, 45.5, 60.5, 110.5

Typical range of values: 0.5 ≤ Radius ≤ 511.5 (lin)

Minimum increment: 1.0

Recommended increment: 1.0

## Example (C++ (HALCON 5.0-10.0))

```#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);
}
```

## Complexity

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

## Result

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:

• no region: set_system('no_object_result',<RegionResult>)

• empty region: set_system('empty_region_result',<RegionResult>)

Otherwise, an exception is raised.