# ImageMask

VTKExamples/Cxx/Images/ImageMask

### Description

This example creates an all red image. Then it creates a mask of a small rectangle. The red pixels in this rectangle are copied to the output image, while the rest of the output image is black. The black region could be set to a different color using SetMaskedOutputValue.

### Code

ImageMask.cxx

    #include <vtkSmartPointer.h>
    #include <vtkImageData.h>
    #include <vtkImageMapper3D.h>
    #include <vtkJPEGWriter.h>
    #include <vtkImageCanvasSource2D.h>
    #include <vtkImageMask.h>
    #include <vtkRenderWindow.h>
    #include <vtkRenderWindowInteractor.h>
    #include <vtkInteractorStyleImage.h>
    #include <vtkRenderer.h>
    #include <vtkJPEGReader.h>
    #include <vtkImageActor.h>
    #include <vtkImageEllipsoidSource.h>
    #include <vtkImageCast.h>

    int main(int, char *[])
    {
      // Create an image of a rectangle
      vtkSmartPointer<vtkImageCanvasSource2D> source =
        vtkSmartPointer<vtkImageCanvasSource2D>::New();
      source->SetScalarTypeToUnsignedChar();
      source->SetNumberOfScalarComponents(3);
      source->SetExtent(0, 200, 0, 200, 0, 0);

      // Create a red image
      source->SetDrawColor(255,0,0);
      source->FillBox(0,200,0,200);

      source->Update();

      // Create a rectanglular mask
      vtkSmartPointer<vtkImageCanvasSource2D> maskSource =
        vtkSmartPointer<vtkImageCanvasSource2D>::New();
      maskSource->SetScalarTypeToUnsignedChar();
      maskSource->SetNumberOfScalarComponents(1);
      maskSource->SetExtent(0, 200, 0, 200, 0, 0);

      // Initialize the mask to black
      maskSource->SetDrawColor(0,0,0);
      maskSource->FillBox(0,200,0,200);

      // Create a square
      maskSource->SetDrawColor(255,255,255); //anything non-zero means "make the output pixel equal the input pixel." If the mask is zero, the output pixel is set to MaskedValue
      maskSource->FillBox(100,120,100,120);
      maskSource->Update();

      vtkSmartPointer<vtkImageMask> maskFilter =
        vtkSmartPointer<vtkImageMask>::New();
      maskFilter->SetInputConnection(0, source->GetOutputPort());
      maskFilter->SetInputConnection(1, maskSource->GetOutputPort());
      maskFilter->SetMaskedOutputValue(0,1,0);
      maskFilter->Update();

      vtkSmartPointer<vtkImageMask> inverseMaskFilter =
        vtkSmartPointer<vtkImageMask>::New();
      inverseMaskFilter->SetInputConnection(0, source->GetOutputPort());
      inverseMaskFilter->SetInputConnection(1, maskSource->GetOutputPort());
      inverseMaskFilter->SetMaskedOutputValue(0,1,0);
      inverseMaskFilter->NotMaskOn();
      inverseMaskFilter->Update();

      // Create actors
      vtkSmartPointer<vtkImageActor> originalActor =
        vtkSmartPointer<vtkImageActor>::New();
      originalActor->GetMapper()->SetInputConnection(source->GetOutputPort());

      vtkSmartPointer<vtkImageActor> maskActor =
        vtkSmartPointer<vtkImageActor>::New();
      maskActor->GetMapper()->SetInputConnection(maskSource->GetOutputPort());

      vtkSmartPointer<vtkImageActor> maskedActor =
        vtkSmartPointer<vtkImageActor>::New();
      maskedActor->GetMapper()->SetInputConnection(maskFilter->GetOutputPort());

      vtkSmartPointer<vtkImageActor> inverseMaskedActor =
        vtkSmartPointer<vtkImageActor>::New();
      inverseMaskedActor->GetMapper()->SetInputConnection(inverseMaskFilter->GetOutputPort());

      // Define viewport ranges
      // (xmin, ymin, xmax, ymax)
      double originalViewport[4] = {0.0, 0.0, 0.25, 1.0};
      double maskViewport[4] = {0.25, 0.0, 0.5, 1.0};
      double maskedViewport[4] = {0.5, 0.0, 0.75, 1.0};
      double inverseMaskedViewport[4] = {0.75, 0.0, 1.0, 1.0};

      // Setup renderers
      vtkSmartPointer<vtkRenderer> originalRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      originalRenderer->SetViewport(originalViewport);
      originalRenderer->AddActor(originalActor);
      originalRenderer->ResetCamera();
      originalRenderer->SetBackground(.4, .5, .6);

      vtkSmartPointer<vtkRenderer> maskRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      maskRenderer->SetViewport(maskViewport);
      maskRenderer->AddActor(maskActor);
      maskRenderer->ResetCamera();
      maskRenderer->SetBackground(.4, .5, .6);

      vtkSmartPointer<vtkRenderer> maskedRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      maskedRenderer->SetViewport(maskedViewport);
      maskedRenderer->AddActor(maskedActor);
      maskedRenderer->ResetCamera();
      maskedRenderer->SetBackground(.4, .5, .6);

      vtkSmartPointer<vtkRenderer> inverseMaskedRenderer =
        vtkSmartPointer<vtkRenderer>::New();
      inverseMaskedRenderer->SetViewport(inverseMaskedViewport);
      inverseMaskedRenderer->AddActor(inverseMaskedActor);
      inverseMaskedRenderer->ResetCamera();
      inverseMaskedRenderer->SetBackground(.4, .5, .7);

      vtkSmartPointer<vtkRenderWindow> renderWindow =
        vtkSmartPointer<vtkRenderWindow>::New();
      renderWindow->SetSize(1000, 250);
      renderWindow->AddRenderer(originalRenderer);
      renderWindow->AddRenderer(maskRenderer);
      renderWindow->AddRenderer(maskedRenderer);
      renderWindow->AddRenderer(inverseMaskedRenderer);

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

      renderWindowInteractor->SetInteractorStyle(style);

      renderWindowInteractor->SetRenderWindow(renderWindow);
      renderWindowInteractor->Initialize();

      renderWindowInteractor->Start();

      return EXIT_SUCCESS;
    }

### CMakeLists.txt

    cmake_minimum_required(VERSION 2.8)

    PROJECT(ImageMask)

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

    add_executable(ImageMask MACOSX_BUNDLE ImageMask.cxx)

    target_link_libraries(ImageMask ${VTK_LIBRARIES})

### Download and Build ImageMask

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

    cd ImageMask/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:

    ./ImageMask

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.