# ImageIterator

VTKExamples/Cxx/ImageData/ImageIterator

### Description

Extracts an extent from an image using an image iterator.

### Code

ImageIterator.cxx

    #include <vtkVersion.h>

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

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

      // Specify the size of the image data
      imageData->SetDimensions(10,20,30);
    #if VTK_MAJOR_VERSION <= 5
      imageData->SetNumberOfScalarComponents(3);
      imageData->SetScalarTypeToDouble();
      imageData->AllocateScalars();
    #else
      imageData->AllocateScalars(VTK_DOUBLE,3);
    #endif

      // Fill every entry of the image data with x,y,z
      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())
      {
        double* valIt = it.BeginSpan();
        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;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ImageIterator)

    find_package(VTK REQUIRED)
    include(${VTK_USE_FILE})

    add_executable(ImageIterator MACOSX_BUNDLE ImageIterator.cxx )

    target_link_libraries(ImageIterator ${VTK_LIBRARIES})

### Download and Build ImageIterator

Click here to download ImageIterator and its CMakeLists.txt file. Once the tarball ImageIterator.tar has been downloaded and extracted,

    cd ImageIterator/build

If VTK is installed:

    cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

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

Build the project:

    make

and run it:

    ./ImageIterator

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.