Method PolygonalizeImage

Filters/Hybrid/vtkImageToPolyDataFilter.cxx:358–432

}

void vtkImageToPolyDataFilter::PolygonalizeImage(vtkUnsignedCharArray* pixels, int dims[3],
  double origin[3], double spacing[3], vtkPolyData* output)
{
  int numPolys;
  int numPixels = dims[0] * dims[1];

  // Perform connected traversal on quantized points. This builds
  // the initial "polygons" in implicit form.
  //
  this->PolyColors = vtkUnsignedCharArray::New();
  this->PolyColors->SetNumberOfComponents(3);
  this->PolyColors->Allocate(5000);

  numPolys = this->ProcessImage(pixels, dims);
  vtkDebugMacro(<< "Visited regions..." << numPolys << " polygons");

  // Build edges around the boundary of the polygons. Also identify
  // junction points where 3 or 4 polygons meet.
  //
  vtkPoints* points = vtkPoints::New();
  points->Allocate(numPixels / 2, numPixels / 2);

  vtkUnsignedCharArray* pointDescr = vtkUnsignedCharArray::New();
  pointDescr->Allocate(numPixels / 2, numPixels / 2);

  vtkCellArray* edgeConn = vtkCellArray::New();
  edgeConn->AllocateEstimate(numPixels / 2, 1);
  vtkPolyData* edges = vtkPolyData::New();
  edges->SetPoints(points);
  edges->SetLines(edgeConn);
  points->Delete();
  edgeConn->Delete();

  this->BuildEdges(pixels, dims, origin, spacing, pointDescr, edges);
  vtkDebugMacro(<< "Edges built...");

  // Now that we've got the edges, we have to build the "loops" around the
  // polygons that define the polygon explicitly.
  //
  vtkUnsignedCharArray* polyColors = vtkUnsignedCharArray::New();
  polyColors->SetNumberOfComponents(3);
  polyColors->SetNumberOfValues(numPolys * 3);

  this->BuildPolygons(pointDescr, edges, numPolys, polyColors);
  this->PolyColors->Delete();
  delete[] this->Visited;
  vtkDebugMacro(<< "Constructed polygons...");

  // Smooth edge network. Some points are identified as fixed, others
  // move using Laplacian smoothing.
  //
  if (this->Smoothing)
  {
    this->SmoothEdges(pointDescr, edges);
    vtkDebugMacro(<< "Edges smoothed...");
  }

  // Decimate edge network. There will be colinear vertices along edges.