ImageIterator

#include <vtkImageData.h>
#include <vtkImageIterator.h>
#include <vtkNew.h>

int main(int, char*[])
{
  // Create an image data
  vtkNew<vtkImageData> imageData;

  // Specify the size of the image data
  imageData->SetDimensions(10, 20, 30);
  imageData->AllocateScalars(VTK_DOUBLE, 3);

  // Fill every entry of the image data with x,y,z
  const int* dims = imageData->GetDimensions();
  double* ptr = static_cast<double*>(imageData->GetScalarPointer(0, 0, 0));
  for (int z = 0; z < dims[2]; z++)
  {
    for (int y = 0; y < dims[1]; y++)
    {
      for (int x = 0; x < dims[0]; x++)
      {
        *ptr++ = z;
        *ptr++ = y;
        *ptr++ = x;
      }
    }
  }

  // Define the extent to be extracted
  int extent[6];
  extent[0] = 2;
  extent[1] = 5;
  extent[2] = 2;
  extent[3] = 5;
  extent[4] = 15;
  extent[5] = 15;

  // Retrieve the entries from the image data and print them to the screen
  vtkImageIterator<double> it(imageData, extent);
  while (!it.IsAtEnd())
  {
    const double* valIt = it.BeginSpan();
    const double* valEnd = it.EndSpan();
    while (valIt != valEnd)
    {
      // Increment for each component
      double x = *valIt++;
      double y = *valIt++;
      double z = *valIt++;
      std::cout << "(" << x << "," << y << "," << z << ") ";
    }
    std::cout << std::endl;
    it.NextSpan();
  }

  return EXIT_SUCCESS;
}

cmake_minimum_required(VERSION 3.12 FATAL_ERROR)

project(ImageIterator)

find_package(VTK COMPONENTS 
  CommonCore
  CommonDataModel
)

if (NOT VTK_FOUND)
  message(FATAL_ERROR "ImageIterator: Unable to find the VTK build folder.")
endif()

# Prevent a "command line is too long" failure in Windows.
set(CMAKE_NINJA_FORCE_RESPONSE_FILE "ON" CACHE BOOL "Force Ninja to use response files.")
add_executable(ImageIterator MACOSX_BUNDLE ImageIterator.cxx )
  target_link_libraries(ImageIterator PRIVATE ${VTK_LIBRARIES}
)
# vtk_module_autoinit is needed
vtk_module_autoinit(
  TARGETS ImageIterator
  MODULES ${VTK_LIBRARIES}
)

cd ImageIterator/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./ImageIterator