Add Two Images Together#

Synopsis#

Add two images together.

Results#

../../../../_images/AddTwoImages.png — Output In VTK Image#

Code#

C++#

#include "itkImage.h"
#include "itkRescaleIntensityImageFilter.h"
#include "itkAddImageFilter.h"

#include <itkImageToVTKImageFilter.h>

#include "vtkVersion.h"
#include "vtkImageViewer.h"
#include "vtkImageMapper3D.h"
#include "vtkRenderWindowInteractor.h"
#include "vtkSmartPointer.h"
#include "vtkImageActor.h"
#include "vtkInteractorStyleImage.h"
#include "vtkRenderer.h"

using ImageType = itk::Image<unsigned char, 2>;

static void
CreateImage1(ImageType::Pointer image);
static void
CreateImage2(ImageType::Pointer image);

int
main()
{
  auto image1 = ImageType::New();
  CreateImage1(image1);

  auto image2 = ImageType::New();
  CreateImage2(image2);

  using AddImageFilterType = itk::AddImageFilter<ImageType, ImageType>;

  auto addFilter = AddImageFilterType::New();
  addFilter->SetInput1(image1);
  addFilter->SetInput2(image2);
  addFilter->Update();

  // Visualize first image
  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
  auto connector1 = ConnectorType::New();
  connector1->SetInput(image1);

  vtkSmartPointer<vtkImageActor> actor1 = vtkSmartPointer<vtkImageActor>::New();
#if VTK_MAJOR_VERSION <= 5
  actor1->SetInput(connector1->GetOutput());
#else
  connector1->Update();
  actor1->GetMapper()->SetInputData(connector1->GetOutput());
#endif
  // Visualize first image
  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
  auto connector2 = ConnectorType::New();
  connector2->SetInput(image2);

  vtkSmartPointer<vtkImageActor> actor2 = vtkSmartPointer<vtkImageActor>::New();
#if VTK_MAJOR_VERSION <= 5
  actor2->SetInput(connector2->GetOutput());
#else
  connector2->Update();
  actor2->GetMapper()->SetInputData(connector2->GetOutput());
#endif

  // Visualize joined image
  auto addConnector = ConnectorType::New();
  addConnector->SetInput(addFilter->GetOutput());

  vtkSmartPointer<vtkImageActor> addActor = vtkSmartPointer<vtkImageActor>::New();
#if VTK_MAJOR_VERSION <= 5
  addActor->SetInput(addConnector->GetOutput());
#else
  addConnector->Update();
  addActor->GetMapper()->SetInputData(addConnector->GetOutput());
#endif
  // There will be one render window
  vtkSmartPointer<vtkRenderWindow> renderWindow = vtkSmartPointer<vtkRenderWindow>::New();
  renderWindow->SetSize(900, 300);

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

  // Define viewport ranges
  // (xmin, ymin, xmax, ymax)
  double leftViewport[4] = { 0.0, 0.0, 0.33, 1.0 };
  double centerViewport[4] = { 0.33, 0.0, 0.66, 1.0 };
  double rightViewport[4] = { 0.66, 0.0, 1.0, 1.0 };

  // Setup both renderers
  vtkSmartPointer<vtkRenderer> leftRenderer = vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(leftRenderer);
  leftRenderer->SetViewport(leftViewport);
  leftRenderer->SetBackground(.6, .5, .4);

  vtkSmartPointer<vtkRenderer> centerRenderer = vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(centerRenderer);
  centerRenderer->SetViewport(centerViewport);
  centerRenderer->SetBackground(.4, .5, .6);

  vtkSmartPointer<vtkRenderer> rightRenderer = vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(rightRenderer);
  rightRenderer->SetViewport(rightViewport);
  rightRenderer->SetBackground(.4, .5, .6);

  // Add the sphere to the left and the cube to the right
  leftRenderer->AddActor(actor1);
  centerRenderer->AddActor(actor2);
  rightRenderer->AddActor(addActor);

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

  renderWindow->Render();

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

  interactor->Start();

  return EXIT_SUCCESS;
}

void
CreateImage1(ImageType::Pointer image)
{
  // Create an image with 2 connected components
  ImageType::RegionType region;
  ImageType::IndexType  start;
  start[0] = 0;
  start[1] = 0;

  ImageType::SizeType size;
  unsigned int        NumRows = 200;
  unsigned int        NumCols = 300;
  size[0] = NumRows;
  size[1] = NumCols;

  region.SetSize(size);
  region.SetIndex(start);

  image->SetRegions(region);
  image->Allocate();

  // Make a square
  for (unsigned int r = 20; r < 80; ++r)
  {
    for (unsigned int c = 20; c < 80; ++c)
    {
      ImageType::IndexType pixelIndex;
      pixelIndex[0] = r;
      pixelIndex[1] = c;

      image->SetPixel(pixelIndex, 15);
    }
  }
}


void
CreateImage2(ImageType::Pointer image)
{
  // Create an image with 2 connected components
  ImageType::RegionType region;
  ImageType::IndexType  start;
  start[0] = 0;
  start[1] = 0;

  ImageType::SizeType size;
  unsigned int        NumRows = 200;
  unsigned int        NumCols = 300;
  size[0] = NumRows;
  size[1] = NumCols;

  region.SetSize(size);
  region.SetIndex(start);

  image->SetRegions(region);
  image->Allocate();

  // Make another square
  for (unsigned int r = 40; r < 100; ++r)
  {
    for (unsigned int c = 40; c < 100; ++c)
    {
      ImageType::IndexType pixelIndex;
      pixelIndex[0] = r;
      pixelIndex[1] = c;

      image->SetPixel(pixelIndex, 15);
    }
  }
}

Classes demonstrated#

template<typename TInputImage1, typename TInputImage2 = TInputImage1, typename TOutputImage = TInputImage1> class AddImageFilter : public itk::BinaryGeneratorImageFilter<TInputImage1, TInputImage2, TOutputImage>

Pixel-wise addition of two images.

This class is templated over the types of the two input images and the type of the output image. Numeric conversions (castings) are done by the C++ defaults.

The pixel type of the input 1 image must have a valid definition of the operator+ with a pixel type of the image 2. This condition is required because internally this filter will perform the operation

pixel_from_image_1 + pixel_from_image_2

Additionally the type resulting from the sum, will be cast to the pixel type of the output image.

The total operation over one pixel will be

output_pixel = static_cast<OutputPixelType>( input1_pixel + input2_pixel )

For example, this filter could be used directly for adding images whose pixels are vectors of the same dimension, and to store the resulting vector in an output image of vector pixels.

The images to be added are set using the methods:

SetInput1( image1 );
SetInput2( image2 );

Additionally, this filter can be used to add a constant to every pixel of an image by using

SetInput1( image1 );
SetConstant2( constant );

Warning

No numeric overflow checking is performed in this filter.

ITK Sphinx Examples:

All ITK Sphinx Examples

Add Two Images Together

Add Constant To Every Pixel

See itk::AddImageFilter for additional documentation.