Connected Components In Image

Warning

Fix Problem Contains problems not fixed from original wiki.

Synopsis

Find connected components in an image.

Results

Note

Help Wanted Implementation of Results for sphinx examples containing this message. Reconfiguration of CMakeList.txt may be necessary. Write An Example <https://itk.org/ITKExamples/Documentation/Contribute/WriteANewExample.html>

Code

C++

#include "itkImage.h"
#include "itkImageFileWriter.h"
#include "itkConnectedThresholdImageFilter.h"
#include "itkCastImageFilter.h"

#include <itkImageToVTKImageFilter.h>

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

using PixelType = unsigned char;
constexpr size_t Dimension = 3;
using ImageType = itk::Image<PixelType, Dimension>;

static void
CreateImage(ImageType::Pointer image);

int
main(int argc, char * argv[])
{
  ImageType::Pointer image = ImageType::New();
  CreateImage(image);

  using ConnectedFilterType = itk::ConnectedThresholdImageFilter<ImageType, ImageType>;
  ConnectedFilterType::Pointer connectedThreshold = ConnectedFilterType::New();
  float                        lower = 95.0;
  float                        upper = 105.0;
  connectedThreshold->SetLower(lower);
  connectedThreshold->SetUpper(upper);

  connectedThreshold->SetReplaceValue(255);

  // Seed 1: (25, 35)
  ImageType::IndexType seed1;
  seed1[0] = 25;
  seed1[1] = 35;
  connectedThreshold->SetSeed(seed1);
  connectedThreshold->SetInput(image);

  // Seed 2: (110, 120)
  ImageType::IndexType seed2;
  seed2[0] = 110;
  seed2[1] = 120;
  connectedThreshold->SetSeed(seed2);
  connectedThreshold->SetReplaceValue(150);

  connectedThreshold->SetInput(image);

  // Visualize
  using ConnectorType = itk::ImageToVTKImageFilter<ImageType>;
  ConnectorType::Pointer connector2 = ConnectorType::New();
  connector2->SetInput(image);

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

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

  vtkSmartPointer<vtkImageActor> addActor = vtkSmartPointer<vtkImageActor>::New();
#if VTK_MAJOR_VERSION <= 5
  addActor->SetInput(connector->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
CreateImage(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;
  size[0] = 200;
  size[1] = 300;

  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 = 30; c < 100; c++)
    {
      ImageType::IndexType pixelIndex;
      pixelIndex[0] = r;
      pixelIndex[1] = c;

      image->SetPixel(pixelIndex, 100.0);
    }
  }

  // Make another square
  for (unsigned int r = 100; r < 130; r++)
  {
    for (unsigned int c = 115; c < 160; c++)
    {
      ImageType::IndexType pixelIndex;
      pixelIndex[0] = r;
      pixelIndex[1] = c;

      image->SetPixel(pixelIndex, 100.0);
    }
  }
}

Classes demonstrated