ImageDifference

VTKExamples/Cxx/Images/ImageDifference


Description

This example makes a large square and a smaller square and subtracts them, leaving the outline of a square.

Code

ImageDifference.cxx

#include <vtkSmartPointer.h>
#include <vtkImageData.h>
#include <vtkImageMapper3D.h>
#include <vtkImageCanvasSource2D.h>
#include <vtkImageDifference.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkProperty.h>
#include <vtkRenderer.h>
#include <vtkImageActor.h>

int main(int, char *[])
{
  // Create an image
  vtkSmartPointer<vtkImageCanvasSource2D> source1 = 
    vtkSmartPointer<vtkImageCanvasSource2D>::New();
  source1->SetScalarTypeToUnsignedChar();
  source1->SetNumberOfScalarComponents(3);
  source1->SetExtent(0, 100, 0, 100, 0, 0);
  source1->SetDrawColor(0,0,0,1);
  source1->FillBox(0, 100, 0, 100);
  source1->SetDrawColor(255,0,0,1);
  source1->FillBox(10, 90, 10, 90);
  source1->Update();

  // Create another image
  vtkSmartPointer<vtkImageCanvasSource2D> source2 = 
    vtkSmartPointer<vtkImageCanvasSource2D>::New();
  source2->SetScalarTypeToUnsignedChar();
  source2->SetNumberOfScalarComponents(3);
  source2->SetExtent(0, 100, 0, 100, 0, 0);
  source2->SetDrawColor(0,0,0,1);
  source2->FillBox(0, 100, 0, 100);
  source2->SetDrawColor(255,0,0,1);
  source2->FillBox(20, 80, 20, 80);
  source2->Update();

  vtkSmartPointer<vtkImageDifference> differenceFilter = 
    vtkSmartPointer<vtkImageDifference>::New();

  differenceFilter->SetInputConnection(source1->GetOutputPort());
  differenceFilter->SetImageConnection(source2->GetOutputPort());
  differenceFilter->Update();

  // 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 render window
  vtkSmartPointer<vtkRenderWindow> renderWindow = 
    vtkSmartPointer<vtkRenderWindow>::New();

  // Setup renderers
  vtkSmartPointer<vtkRenderer> leftRenderer = 
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(leftRenderer);
  leftRenderer->SetViewport(leftViewport);
  vtkSmartPointer<vtkImageActor> leftActor = 
    vtkSmartPointer<vtkImageActor>::New();
  leftActor->GetMapper()->SetInputConnection(source1->GetOutputPort());
  leftRenderer->AddActor(leftActor);

  vtkSmartPointer<vtkRenderer> centerRenderer = 
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(centerRenderer);
  centerRenderer->SetViewport(centerViewport);
  vtkSmartPointer<vtkImageActor> centerActor = 
    vtkSmartPointer<vtkImageActor>::New();
  centerActor->GetMapper()->SetInputConnection(source2->GetOutputPort());
  centerRenderer->AddActor(centerActor);

  vtkSmartPointer<vtkRenderer> rightRenderer = 
    vtkSmartPointer<vtkRenderer>::New();
  renderWindow->AddRenderer(rightRenderer);
  rightRenderer->SetViewport(rightViewport);
  vtkSmartPointer<vtkImageActor> rightActor = 
    vtkSmartPointer<vtkImageActor>::New();
  rightActor->GetMapper()->SetInputConnection(differenceFilter->GetOutputPort());
  rightRenderer->AddActor(rightActor);

  // Setup render window interactor
  vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor = 
    vtkSmartPointer<vtkRenderWindowInteractor>::New();

  // Render and start interaction
  renderWindowInteractor->SetRenderWindow ( renderWindow );
  renderWindowInteractor->Initialize();

  renderWindowInteractor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(ImageDifference)

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

Download and Build ImageDifference

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

cd ImageDifference/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:

./ImageDifference

WINDOWS USERS

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