# PolyDataToImageData

VTKExamples/Cxx/PolyData/PolyDataToImageData

### Description

- Contributed by: Lars Friedrich

This example generates a sphere (prerequisite: closed surface of type vtkPolyData) and converts it into volume representation vtkImageData) where the foreground voxels are 255 (inside) and the background voxels are 0 (outside). Internally vtkPolyDataToImageStencil is utilized. The resultant image is saved to disk in metaimage file format (SphereVolume.mhd).

### Code

PolyDataToImageData.cxx

    #include <vtkVersion.h>
    #include <vtkSmartPointer.h>
    #include <vtkPolyData.h>
    #include <vtkImageData.h>
    #include <vtkSphereSource.h>
    #include <vtkMetaImageWriter.h>
    #include <vtkPolyDataToImageStencil.h>
    #include <vtkImageStencil.h>
    #include <vtkPointData.h>

    /**
     * This program generates a sphere (closed surface, vtkPolyData) and converts it into volume
     * representation (vtkImageData) where the foreground voxels are 1 and the background voxels are
     * 0. Internally vtkPolyDataToImageStencil is utilized. The resultant image is saved to disk
     * in metaimage file format (SphereVolume.mhd).
     */
    int main(int, char *[])
    {
      vtkSmartPointer<vtkSphereSource> sphereSource =
        vtkSmartPointer<vtkSphereSource>::New();
      sphereSource->SetRadius(20);
      sphereSource->SetPhiResolution(30);
      sphereSource->SetThetaResolution(30);
      vtkSmartPointer<vtkPolyData> pd = sphereSource->GetOutput();
      sphereSource->Update();

      vtkSmartPointer<vtkImageData> whiteImage =
        vtkSmartPointer<vtkImageData>::New();
      double bounds[6];
      pd->GetBounds(bounds);
      double spacing[3]; // desired volume spacing
      spacing[0] = 0.5;
      spacing[1] = 0.5;
      spacing[2] = 0.5;
      whiteImage->SetSpacing(spacing);

      // compute dimensions
      int dim[3];
      for (int i = 0; i < 3; i++)
      {
        dim[i] = static_cast<int>(ceil((bounds[i * 2 + 1] - bounds[i * 2]) / spacing[i]));
      }
      whiteImage->SetDimensions(dim);
      whiteImage->SetExtent(0, dim[0] - 1, 0, dim[1] - 1, 0, dim[2] - 1);

      double origin[3];
      origin[0] = bounds[0] + spacing[0] / 2;
      origin[1] = bounds[2] + spacing[1] / 2;
      origin[2] = bounds[4] + spacing[2] / 2;
      whiteImage->SetOrigin(origin);

    #if VTK_MAJOR_VERSION <= 5
      whiteImage->SetScalarTypeToUnsignedChar();
      whiteImage->AllocateScalars();
    #else
      whiteImage->AllocateScalars(VTK_UNSIGNED_CHAR,1);
    #endif
      // fill the image with foreground voxels:
      unsigned char inval = 255;
      unsigned char outval = 0;
      vtkIdType count = whiteImage->GetNumberOfPoints();
      for (vtkIdType i = 0; i < count; ++i)
      {
        whiteImage->GetPointData()->GetScalars()->SetTuple1(i, inval);
      }

      // polygonal data --> image stencil:
      vtkSmartPointer<vtkPolyDataToImageStencil> pol2stenc =
        vtkSmartPointer<vtkPolyDataToImageStencil>::New();
    #if VTK_MAJOR_VERSION <= 5
      pol2stenc->SetInput(pd);
    #else
      pol2stenc->SetInputData(pd);
    #endif
      pol2stenc->SetOutputOrigin(origin);
      pol2stenc->SetOutputSpacing(spacing);
      pol2stenc->SetOutputWholeExtent(whiteImage->GetExtent());
      pol2stenc->Update();

      // cut the corresponding white image and set the background:
      vtkSmartPointer<vtkImageStencil> imgstenc =
        vtkSmartPointer<vtkImageStencil>::New();
    #if VTK_MAJOR_VERSION <= 5
      imgstenc->SetInput(whiteImage);
      imgstenc->SetStencil(pol2stenc->GetOutput());
    #else
      imgstenc->SetInputData(whiteImage);
      imgstenc->SetStencilConnection(pol2stenc->GetOutputPort());
    #endif
      imgstenc->ReverseStencilOff();
      imgstenc->SetBackgroundValue(outval);
      imgstenc->Update();

      vtkSmartPointer<vtkMetaImageWriter> writer =
        vtkSmartPointer<vtkMetaImageWriter>::New();
      writer->SetFileName("SphereVolume.mhd");
    #if VTK_MAJOR_VERSION <= 5
      writer->SetInput(imgstenc->GetOutput());
    #else
      writer->SetInputData(imgstenc->GetOutput());
    #endif
      writer->Write();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(PolyDataToImageData)

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

    add_executable(PolyDataToImageData MACOSX_BUNDLE PolyDataToImageData.cxx )

    target_link_libraries(PolyDataToImageData ${VTK_LIBRARIES})

### Download and Build PolyDataToImageData

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

    cd PolyDataToImageData/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:

    ./PolyDataToImageData

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.