# GraphAlgorithmFilter

VTKExamples/Cxx/Developers/GraphAlgorithmFilter

### Description

This example demonstrates how to create a filter that takes a vtkGraph as input and produces a vtkGraph as output.

### Code

GraphAlgorithmFilter.cxx

    #include <vtkVersion.h>
    #include <vtkSmartPointer.h>
    #include <vtkGraph.h>
    #include <vtkMutableUndirectedGraph.h>
    #include <vtkMutableDirectedGraph.h>

    #include "vtkTestGraphAlgorithmFilter.h"

    void TestDirected();
    void TestUndirected();

    int main(int, char *[])
    {
      TestDirected();
      TestUndirected();

      return EXIT_SUCCESS;
    }

    void TestDirected()
    {

      vtkSmartPointer<vtkMutableDirectedGraph> g =
        vtkSmartPointer<vtkMutableDirectedGraph>::New();
      vtkIdType v1 = g->AddVertex();
      vtkIdType v2 = g->AddVertex();

      g->AddEdge(v1, v2);
      std::cout << "Input type: " << g->GetClassName() << std::endl;

      vtkSmartPointer<vtkTestGraphAlgorithmFilter> filter =
        vtkSmartPointer<vtkTestGraphAlgorithmFilter>::New();
    #if VTK_MAJOR_VERSION <= 5
      filter->SetInput(g);
    #else
      filter->SetInputData(g);
    #endif
      filter->Update();

      std::cout << "Output type: " << filter->GetOutput()->GetClassName() << std::endl;
      std::cout << "Output has " << filter->GetOutput()->GetNumberOfVertices() << " vertices." << std::endl;
      std::cout << std::endl;
    }

    void TestUndirected()
    {
      std::cout << "TestUndirected" << std::endl;
      vtkSmartPointer<vtkMutableUndirectedGraph> g =
        vtkSmartPointer<vtkMutableUndirectedGraph>::New();
      vtkIdType v1 = g->AddVertex();
      vtkIdType v2 = g->AddVertex();

      g->AddEdge(v1, v2);
      std::cout << "Input type: " << g->GetClassName() << std::endl;

      vtkSmartPointer<vtkTestGraphAlgorithmFilter> filter =
        vtkSmartPointer<vtkTestGraphAlgorithmFilter>::New();
    #if VTK_MAJOR_VERSION <= 5
      filter->SetInput(g);
    #else
      filter->SetInputData(g);
    #endif
      filter->Update();

      std::cout << "Output type: " << filter->GetOutput()->GetClassName() << std::endl;
      std::cout << "Output has " << filter->GetOutput()->GetNumberOfVertices() << " vertices." << std::endl;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(GraphAlgorithmFilter)

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

    add_executable(GraphAlgorithmFilter MACOSX_BUNDLE GraphAlgorithmFilter.cxx)

    target_link_libraries(GraphAlgorithmFilter ${VTK_LIBRARIES})

### Download and Build GraphAlgorithmFilter

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

    cd GraphAlgorithmFilter/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:

    ./GraphAlgorithmFilter

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.