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CannyEdgeDetector

vtk-examples/Cxx/Images/CannyEdgeDetector


Question

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Code

CannyEdgeDetector.cxx

#include <vtkCamera.h>
#include <vtkGeometryFilter.h>
#include <vtkImageActor.h>
#include <vtkImageCast.h>
#include <vtkImageConstantPad.h>
#include <vtkImageGaussianSmooth.h>
#include <vtkImageGradient.h>
#include <vtkImageLuminance.h>
#include <vtkImageMagnitude.h>
#include <vtkImageNonMaximumSuppression.h>
#include <vtkImageToStructuredPoints.h>
#include <vtkLinkEdgels.h>
#include <vtkNamedColors.h>
#include <vtkNew.h>
#include <vtkPNGReader.h>
#include <vtkPolyDataMapper.h>
#include <vtkProperty.h>
#include <vtkRenderWindow.h>
#include <vtkRenderWindowInteractor.h>
#include <vtkRenderer.h>
#include <vtkStripper.h>
#include <vtkStructuredPoints.h>
#include <vtkSubPixelPositionEdgels.h>
#include <vtkThreshold.h>

int main(int argc, char* argv[])
{
  vtkNew<vtkNamedColors> colors;

  if (argc != 2)
  {
    std::cerr << "Required args: filename.png e.g. Gourds.png" << std::endl;
    return EXIT_FAILURE;
  }

  std::string filename = argv[1];

  // Define viewport ranges
  // (xmin, ymin, xmax, ymax)
  double originalViewport[4] = {0.0, 0.0, 0.5, 1.0};
  double edgeViewport[4] = {0.5, 0.0, 1.0, 1.0};

  vtkNew<vtkRenderer> originalRenderer;
  originalRenderer->SetViewport(originalViewport);
  originalRenderer->SetBackground(colors->GetColor3d("SlateGray").GetData());
  vtkNew<vtkRenderer> edgeRenderer;
  edgeRenderer->SetViewport(edgeViewport);
  edgeRenderer->SetBackground(colors->GetColor3d("LightSlateGray").GetData());

  vtkNew<vtkRenderWindow> renderWindow;
  renderWindow->SetSize(600, 300);
  renderWindow->SetMultiSamples(0);
  renderWindow->AddRenderer(originalRenderer);
  renderWindow->AddRenderer(edgeRenderer);
  renderWindow->SetWindowName("CannyEdgeDetector");

  vtkNew<vtkRenderWindowInteractor> interactor;
  interactor->SetRenderWindow(renderWindow);

  vtkNew<vtkPNGReader> imageIn;
  imageIn->SetFileName(filename.c_str());
  imageIn->Update();

  vtkNew<vtkImageActor> imageActor;
  imageActor->SetInputData(imageIn->GetOutput());

  originalRenderer->AddActor(imageActor);

  vtkNew<vtkImageLuminance> il;
  il->SetInputConnection(imageIn->GetOutputPort());

  vtkNew<vtkImageCast> ic;
  ic->SetOutputScalarTypeToFloat();
  ic->SetInputConnection(il->GetOutputPort());

  // Smooth the image
  vtkNew<vtkImageGaussianSmooth> gs;
  gs->SetInputConnection(ic->GetOutputPort());
  gs->SetDimensionality(2);
  gs->SetRadiusFactors(1, 1, 0);

  // Gradient the image
  vtkNew<vtkImageGradient> imgGradient;
  imgGradient->SetInputConnection(gs->GetOutputPort());
  imgGradient->SetDimensionality(2);

  vtkNew<vtkImageMagnitude> imgMagnitude;
  imgMagnitude->SetInputConnection(imgGradient->GetOutputPort());

  // Non maximum suppression
  vtkNew<vtkImageNonMaximumSuppression> nonMax;
  imgMagnitude->Update();
  nonMax->SetMagnitudeInputData(imgMagnitude->GetOutput());
  imgGradient->Update();
  nonMax->SetVectorInputData(imgGradient->GetOutput());
  nonMax->SetDimensionality(2);

  vtkNew<vtkImageConstantPad> pad;
  pad->SetInputConnection(imgGradient->GetOutputPort());
  pad->SetOutputNumberOfScalarComponents(3);
  pad->SetConstant(0);

  vtkNew<vtkImageToStructuredPoints> i2sp1;
  i2sp1->SetInputConnection(nonMax->GetOutputPort());
  pad->Update();
  i2sp1->SetVectorInputData(pad->GetOutput());

  // Link edgles
  vtkNew<vtkLinkEdgels> imgLink;
  imgLink->SetInputConnection(i2sp1->GetOutputPort());
  imgLink->SetGradientThreshold(2);

  // Threshold links
  vtkNew<vtkThreshold> thresholdEdges;
  thresholdEdges->SetInputConnection(imgLink->GetOutputPort());
  thresholdEdges->SetUpperThreshold(10);
  thresholdEdges->SetThresholdFunction(vtkThreshold::THRESHOLD_UPPER);
  thresholdEdges->AllScalarsOff();

  vtkNew<vtkGeometryFilter> gf;
  gf->SetInputConnection(thresholdEdges->GetOutputPort());

  vtkNew<vtkImageToStructuredPoints> i2sp;
  i2sp->SetInputConnection(imgMagnitude->GetOutputPort());
  pad->Update();
  i2sp->SetVectorInputData(pad->GetOutput());

  // Subpixel them
  vtkNew<vtkSubPixelPositionEdgels> spe;
  spe->SetInputConnection(gf->GetOutputPort());
  i2sp->Update();
  spe->SetGradMapsData(i2sp->GetStructuredPointsOutput());

  vtkNew<vtkStripper> strip;
  strip->SetInputConnection(spe->GetOutputPort());

  vtkNew<vtkPolyDataMapper> dsm;
  dsm->SetInputConnection(strip->GetOutputPort());
  dsm->ScalarVisibilityOff();

  vtkNew<vtkActor> planeActor;
  planeActor->SetMapper(dsm);
  planeActor->GetProperty()->SetAmbient(1.0);
  planeActor->GetProperty()->SetDiffuse(0.0);
  planeActor->GetProperty()->SetColor(
      colors->GetColor3d("GhostWhite").GetData());

  // Add the actors to the renderer, set the background and size
  edgeRenderer->AddActor(planeActor);

  // Render the image
  interactor->Initialize();
  renderWindow->Render();
  renderWindow->Render();

  interactor->Start();

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(CannyEdgeDetector)

find_package(VTK COMPONENTS 
  vtkCommonColor
  vtkCommonCore
  vtkCommonDataModel
  vtkCommonExecutionModel
  vtkFiltersCore
  vtkFiltersGeneral
  vtkFiltersGeometry
  vtkIOImage
  vtkImagingColor
  vtkImagingCore
  vtkImagingGeneral
  vtkImagingMath
  vtkImagingMorphological
  vtkInteractionStyle
  vtkRenderingContextOpenGL2
  vtkRenderingCore
  vtkRenderingFreeType
  vtkRenderingGL2PSOpenGL2
  vtkRenderingOpenGL2
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping CannyEdgeDetector: ${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(CannyEdgeDetector MACOSX_BUNDLE CannyEdgeDetector.cxx )
  target_link_libraries(CannyEdgeDetector PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(CannyEdgeDetector MACOSX_BUNDLE CannyEdgeDetector.cxx )
  target_link_libraries(CannyEdgeDetector PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS CannyEdgeDetector
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build CannyEdgeDetector

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

cd CannyEdgeDetector/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:

./CannyEdgeDetector

WINDOWS USERS

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