# ImageRegion

VTKExamples/Cxx/Interaction/ImageRegion

### Description

This example shows how to get the image coordinates of the corners of a BorderWidget.

It currently says the pick for the lower left corner of the border widget is valid even when it is off the image.

### Code

ImageRegion.cxx

    #include <vtkSmartPointer.h>
    #include <vtkActor.h>
    #include <vtkAssemblyNode.h>
    #include <vtkAssemblyPath.h>
    #include <vtkBorderRepresentation.h>
    #include <vtkBorderWidget.h>
    #include <vtkCommand.h>
    #include <vtkCoordinate.h>
    #include <vtkImageMapper3D.h>
    #include <vtkImageActor.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkJPEGReader.h>
    #include <vtkPolyData.h>
    #include <vtkPropPicker.h>
    #include <vtkProperty2D.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkRenderer.h>

    class vtkBorderCallback : public vtkCommand
    {
    public:
      vtkBorderCallback(){}

      static vtkBorderCallback *New()
      {
        return new vtkBorderCallback;
      }

      virtual void Execute(vtkObject *caller, unsigned long, void*)
      {
        vtkBorderWidget *borderWidget =
          reinterpret_cast<vtkBorderWidget*>(caller);

        // Get the display coordinates of the two corners of the box
        vtkCoordinate* lowerLeftCoordinate = static_cast<vtkBorderRepresentation*>
           (borderWidget->GetRepresentation())->GetPositionCoordinate();
        double* lowerLeft;
        lowerLeft = lowerLeftCoordinate ->GetComputedWorldValue(this->Renderer);
        std::cout << "Lower left coordinate: " << lowerLeft[0] << ", " << lowerLeft[1] << std::endl;
        lowerLeft[2] = 0;

        vtkCoordinate* upperRightCoordinate = static_cast<vtkBorderRepresentation*>
           (borderWidget->GetRepresentation())->GetPosition2Coordinate();
        double* upperRight;
        upperRight = upperRightCoordinate ->GetComputedWorldValue(this->Renderer);
        std::cout << "Upper right coordinate: " << upperRight[0] << ", " << upperRight[1] << std::endl;
        upperRight[2] = 0;

        // Pick at the two corners of the box
        vtkSmartPointer<vtkPropPicker> picker =
          vtkSmartPointer<vtkPropPicker>::New();

    //    int valid1 = picker->Pick( lowerLeft[0],
        picker->Pick( lowerLeft[0],
                      lowerLeft[1], 0.0, this->Renderer );

        vtkAssemblyPath* path = picker->GetPath();

        vtkProp* pickedProp = NULL;

        bool validPick = false;
        if( path )
        {
          std::cout << "There are " << path->GetNumberOfItems() << " items in the path." << std::endl;
          vtkCollectionSimpleIterator sit;
          path->InitTraversal( sit );
          vtkAssemblyNode *node;
          for( int i = 0; i < path->GetNumberOfItems(); ++i )
          {
            node = path->GetNextNode( sit );
            pickedProp = node->GetViewProp();
            if( this->ImageActor == vtkImageActor::SafeDownCast( pickedProp ) )
            {
              std::cout << "Correct actor picked." << std::endl;
              validPick = true;
              break;
            }
          }
        }

        if(!validPick)
        {
          std::cout << "Off Image" << std::endl;
        }
        else
        {
          double pos1[3];
          picker->GetPickPosition( pos1 );
          std::cout << "Lower Left Pick: " << pos1[0] << " " << pos1[1] << std::endl;
        }
        /*
          if(valid1 != 0)
            {
            std::cout << "Valid1: " << valid1 << std::endl;
            double pos1[3];
            picker->GetPickPosition( pos1 );
            std::cout << "Lower Left Pick: " << pos1[0] << " " << pos1[1] << std::endl;
            }
          else
            {
            std::cout << "Left - nothing was picked" << std::endl;
            }
          */

          /*
          int valid2 = picker->Pick( upperRight[0],
                        upperRight[1], 0.0, this->Renderer );
          if(valid2 != 0)
            {
            std::cout << "Valid2: " << valid2 << std::endl;
            double pos2[3];
            picker->GetPickPosition( pos2 );
            std::cout << "Upper right Pick: " << pos2[0] << " " << pos2[1] << std::endl;
            }
          else
            {
            std::cout << "Right - nothing was picked" << std::endl;
            }
          */
        std::cout << std::endl;
      }

      void SetRenderer(vtkSmartPointer<vtkRenderer> ren) {this->Renderer = ren;}
      void SetImageActor(vtkSmartPointer<vtkImageActor> im) {this->ImageActor = im;}

    private:
      vtkSmartPointer<vtkRenderer> Renderer;
      vtkSmartPointer<vtkImageActor> ImageActor;

    };

    int main (int argc, char *argv[])
    {
      // Parse input arguments
      if ( argc != 2 )
      {
        std::cout << "Usage: " << argv[0]
                  <<" Filename(.jpg)" << std::endl;
        return EXIT_FAILURE;
      }

      std::string InputFilename = argv[1];

      // Read the image
      vtkSmartPointer<vtkJPEGReader> jPEGReader =
        vtkSmartPointer<vtkJPEGReader>::New();
      jPEGReader->SetFileName ( InputFilename.c_str() );

      vtkSmartPointer<vtkImageActor> actor =
        vtkSmartPointer<vtkImageActor>::New();
      actor->GetMapper()->SetInputConnection(jPEGReader->GetOutputPort());

      // A renderer and render window
      vtkSmartPointer<vtkRenderer> renderer =
        vtkSmartPointer<vtkRenderer>::New();
      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->AddRenderer(renderer);

      // An interactor
      vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();
      renderWindowInteractor->SetRenderWindow(renderWindow);

      vtkSmartPointer<vtkInteractorStyleImage> style =
        vtkSmartPointer<vtkInteractorStyleImage>::New();

      renderWindowInteractor->SetInteractorStyle( style );

      vtkSmartPointer<vtkBorderWidget> borderWidget =
        vtkSmartPointer<vtkBorderWidget>::New();
      borderWidget->SetInteractor(renderWindowInteractor);
      static_cast<vtkBorderRepresentation*>(borderWidget->GetRepresentation())->
         GetBorderProperty()->SetColor(1,0,0);
      borderWidget->SelectableOff();

      vtkSmartPointer<vtkBorderCallback> borderCallback =
        vtkSmartPointer<vtkBorderCallback>::New();
      borderCallback->SetRenderer(renderer);
      borderCallback->SetImageActor(actor);

      borderWidget->AddObserver(vtkCommand::InteractionEvent,borderCallback);

      // Add the actors to the scene
      renderer->AddActor(actor);
      renderer->SetBackground(1,1,1);

      renderWindow->Render();
      renderWindowInteractor->Initialize();
      renderWindow->Render();
      borderWidget->On();
      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImageRegion)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkIOImage
      vtkInteractionStyle
      vtkInteractionWidgets
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ImageRegion: ${VTK_NOT_FOUND_MESSAGE}")
      return ()
    endif()
    message (STATUS "VTK_VERSION: ${VTK_VERSION}")
    if (VTK_VERSION VERSION_LESS "8.90.0")
      # old system
      include(${VTK_USE_FILE})
      add_executable(ImageRegion MACOSX_BUNDLE ImageRegion.cxx )
      target_link_libraries(ImageRegion PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ImageRegion MACOSX_BUNDLE ImageRegion.cxx )
      target_link_libraries(ImageRegion PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ImageRegion
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ImageRegion

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

    cd ImageRegion/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:

    ./ImageRegion

WINDOWS USERS

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