VTK/Examples/Cxx/Images/NegativeIndices

#include <vtkVersion.h>
#include <vtkSmartPointer.h>
#include <vtkImageData.h>
 
int main(int, char *[])
{
  // Create an image data
  vtkSmartPointer<vtkImageData> imageData =
    vtkSmartPointer<vtkImageData>::New();
 
  // Specify the size of the image data
  imageData->SetExtent(-5, 5, -5, 5, -5, 5);
 
  // Fill every entry of the image data with "2.0"
  int* extent = imageData->GetExtent();
 
#if VTK_MAJOR_VERSION <= 5
  imageData->SetNumberOfScalarComponents(1);
#else
  imageData->AllocateScalars(VTK_UNSIGNED_CHAR,1);
#endif
 
  std::cout << "Extent: " << " xmin: " << extent[0] << " xmax: " << extent[1]
            << " ymin: " << extent[2] << " ymax: " << extent[3]
            << " zmin: " << extent[4] << " zmax: " << extent[5] << std::endl;
 
 
  for (int z = extent[4]; z < extent[5]; z++)
    {
    for (int y = extent[2]; y < extent[3]; y++)
      {
      for (int x = extent[0]; x < extent[1]; x++)
        {
        imageData->SetScalarComponentFromDouble(x,y,z,0,2.0);
        }
      }
    }
 
  // Retrieve the entries from the image data and print them to the screen
  for (int z = extent[4]; z < extent[5]; z++)
    {
    for (int y = extent[2]; y < extent[3]; y++)
      {
      for (int x = extent[0]; x < extent[1]; x++)
        {
        // Zero is the component, add another loop if you have more
        // than one component
        double v = imageData->GetScalarComponentAsDouble(x,y,z,0);
        // Eo something with v
        std::cout << v << " ";
        }
      std::cout << std::endl;
      }
    std::cout << std::endl;
    }
  return EXIT_SUCCESS;  
}