# ImageClip

VTKExamples/Cxx/Interaction/ImageClip

### Description

This example loads an image into the left half of the window. When you move the border widget (the green square in the bottom left corner) over the image, the region that is selected is displayed in the right half of the window.

### Code

ImageClip.cxx

    #include <vtkSmartPointer.h>
    #include <vtkActor.h>
    #include <vtkBorderRepresentation.h>
    #include <vtkBorderWidget.h>
    #include <vtkCommand.h>
    #include <vtkImageActor.h>
    #include <vtkImageClip.h>
    #include <vtkImageData.h>
    #include <vtkImageMapper3D.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkJPEGReader.h>
    #include <vtkMath.h>
    #include <vtkProperty2D.h>
    #include <vtkRenderer.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkXMLPolyDataReader.h>

    #include <vtkInformation.h>
    #include <vtkStreamingDemandDrivenPipeline.h>

    #include <string>

    class vtkBorderCallback2 : public vtkCommand
    {
    public:
      vtkBorderCallback2(){}

      static vtkBorderCallback2 *New()
      {
        return new vtkBorderCallback2;
      }

      virtual void Execute(vtkObject *caller, unsigned long, void*)
      {

        vtkBorderWidget *borderWidget =
          reinterpret_cast<vtkBorderWidget*>(caller);

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

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

        double* bounds = this->ImageActor->GetBounds();
        double xmin = bounds[0];
        double xmax = bounds[1];
        double ymin = bounds[2];
        double ymax = bounds[3];

        if( (lowerLeft[0] > xmin) &&
            (upperRight[0] < xmax) &&
            (lowerLeft[1] > ymin) &&
            (upperRight[1] < ymax) )
        {
          this->ClipFilter->SetOutputWholeExtent(
            vtkMath::Round(lowerLeft[0]),
            vtkMath::Round(upperRight[0]),
            vtkMath::Round(lowerLeft[1]),
            vtkMath::Round(upperRight[1]), 0, 1);
        }
        else
        {
          std::cout << "box is NOT inside image" << std::endl;
        }
      }

      void SetLeftRenderer(vtkSmartPointer<vtkRenderer> renderer)
        {this->LeftRenderer = renderer;}
      void SetImageActor(vtkSmartPointer<vtkImageActor> actor)
        {this->ImageActor   = actor;}
      void SetClipFilter(vtkSmartPointer<vtkImageClip> clip)
        {this->ClipFilter   = clip;}

    private:
      vtkSmartPointer<vtkRenderer>   LeftRenderer;
      vtkSmartPointer<vtkImageActor> ImageActor;
      vtkSmartPointer<vtkImageClip>  ClipFilter;
    };

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

      std::string inputFilename = argv[1];

      // Read the image
      vtkSmartPointer<vtkJPEGReader> jPEGReader =
        vtkSmartPointer<vtkJPEGReader>::New();

      if( !jPEGReader->CanReadFile( inputFilename.c_str() ) )
      {
        std::cout << "Error: cannot read " << inputFilename << std::endl;
        return EXIT_FAILURE;
      }

      jPEGReader->SetFileName ( inputFilename.c_str() );
      jPEGReader->Update();

      int extent[6];
      jPEGReader->GetOutput()->GetExtent(extent);
      //xmin, xmax, ymin, ymax
      //std::cout << "extent: " << extent[0] << " " << extent[1] << " " <<
      //extent[2] << " " <<  extent[3] << " " <<  extent[4] << " " <<
      //extent[5] << std::endl;

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

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();

      vtkSmartPointer<vtkRenderWindowInteractor> interactor =
        vtkSmartPointer<vtkRenderWindowInteractor>::New();

      vtkSmartPointer<vtkInteractorStyleImage> style =
        vtkSmartPointer<vtkInteractorStyleImage>::New();
      interactor->SetInteractorStyle( style );

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

      interactor->SetRenderWindow(renderWindow);

      // Define viewport ranges in normalized coordinates
      // (xmin, ymin, xmax, ymax)
      double leftViewport[4] = {0.0, 0.0, 0.5, 1.0};
      double rightViewport[4] = {0.5, 0.0, 1.0, 1.0};

      // Setup both renderers
      vtkSmartPointer<vtkRenderer> leftRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      leftRenderer->SetBackground(1,0,0);
      renderWindow->AddRenderer(leftRenderer);
      leftRenderer->SetViewport(leftViewport);

      vtkSmartPointer<vtkRenderer> rightRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      renderWindow->AddRenderer(rightRenderer);
      rightRenderer->SetViewport(rightViewport);

      leftRenderer->AddActor(imageActor);

      leftRenderer->ResetCamera();
      rightRenderer->ResetCamera();

      vtkSmartPointer<vtkImageClip> imageClip =
        vtkSmartPointer<vtkImageClip>::New();
      imageClip->SetInputConnection(jPEGReader->GetOutputPort());
      jPEGReader->UpdateInformation();
      imageClip->SetOutputWholeExtent(
        jPEGReader->GetOutputInformation(0)->Get(
          vtkStreamingDemandDrivenPipeline::WHOLE_EXTENT()));
      imageClip->ClipDataOn();

      vtkSmartPointer<vtkImageActor> clipActor =
        vtkSmartPointer<vtkImageActor>::New();
      clipActor->GetMapper()->SetInputConnection(
        imageClip->GetOutputPort());

      rightRenderer->AddActor(clipActor);

      vtkSmartPointer<vtkBorderCallback2> borderCallback =
        vtkSmartPointer<vtkBorderCallback2>::New();
      borderCallback->SetLeftRenderer(leftRenderer);
      borderCallback->SetImageActor(imageActor);
      borderCallback->SetClipFilter(imageClip);

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

      renderWindow->Render();
      borderWidget->On();
      interactor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

    project(ImageClip)

    find_package(VTK COMPONENTS
      vtkCommonCore
      vtkCommonDataModel
      vtkCommonExecutionModel
      vtkIOImage
      vtkIOXML
      vtkImagingCore
      vtkInteractionStyle
      vtkInteractionWidgets
      vtkRenderingCore
      vtkRenderingFreeType
      vtkRenderingOpenGL2 QUIET)
    if (NOT VTK_FOUND)
      message("Skipping ImageClip: ${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(ImageClip MACOSX_BUNDLE ImageClip.cxx )
      target_link_libraries(ImageClip PRIVATE ${VTK_LIBRARIES})
    else ()
      # include all components
      add_executable(ImageClip MACOSX_BUNDLE ImageClip.cxx )
      target_link_libraries(ImageClip PRIVATE ${VTK_LIBRARIES})
      # vtk_module_autoinit is needed
      vtk_module_autoinit(
        TARGETS ImageClip
        MODULES ${VTK_LIBRARIES}
        )
    endif ()

### Download and Build ImageClip

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

    cd ImageClip/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:

    ./ImageClip

WINDOWS USERS

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