area_center ( Regions : : : Area, Row, Column )

Area and center of regions.

The operator area_center calculates the area and the center of the input regions. The area is defined as the number of pixels of a region. The center is calculated as the mean value of the line or column coordinates, respectively, of all pixels. If more than one region is passed the results are stored in tuples, the index of a value in the tuple corresponding to the index of the input region. In case of empty region all parameters have the value 0.0 if no other behavior was set (see set_system).


Parameters

Regions (input_object)
region(-array) -> object
Region(s) to be examined.

Area (output_control)
integer(-array) -> integer
Area of the region.

Row (output_control)
point.y(-array) -> real
Line index of the center.

Column (output_control)
point.x(-array) -> real
Column index of the center.


Example
#include  
#include  "HCPP.H"

main()
{
  Tuple   area, row, column;

  HImage   img ("affe");
  HWindow  w;

  img.Display (w);
  w.Click ();

  HRegionArray   reg = (img >= 164).Connection ();

  reg.Display (w);
  w.Click ();

  area = reg.AreaCenter (&row, &column);

  for (int i = 0; i < reg.Num (); i++)
  {
    cout << "Row    [" << i << "]" << "= " << row[i].D ();
    cout << "\t\tColumn [" << i << "]" << "= " << column[i].D () << endl;
  }

  cout << "Total number of regions: " << reg.Num () << endl;
  return(0);
}

Complexity

If F is the area of a region the mean runtime complexity is O(sqrt(F)).


Result

The operator area_center returns the value TRUE if the input is not empty. The behavior in case of empty input (no input regions available) is set via the operator set_system(::'no_object_result',<Result>:). The behavior in case of empty region (the region is the empty set) is set via set_system(::'empty_region_result',<Result>:). If necessary an exception is raised.


Possible Predecessors

threshold__, regiongrowing__, connection


See also

select_shape



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