ITK/Examples/EdgesAndGradients/ZeroCrossingBasedEdgeDetectionImageFilter

The zero-crossing based edge detector looks for pixels in the Laplacian of an image where the value of the Laplacian passes through zero --- points where the Laplacian changes sign. Such points often occur at ``edges in images --- i.e. points where the intensity of the image changes rapidly, but they also occur at places that are not as easy to associate with edges.

This example requires an input file and an optional variance.

Contributed by: Bill Lorensen

ZeroCrossingBasedEdgeDetectionImageFilter.cxx

<source lang="cpp">

1. include "itkImage.h"
2. include "itkImageFileReader.h"
3. include "itkImageFileWriter.h"
4. include "itkZeroCrossingBasedEdgeDetectionImageFilter.h"

1. include "itksys/SystemTools.hxx"

1. include "QuickView.h"

int main(int argc, char * argv[]) {

 // Verify command line arguments
 if( argc < 2 )
   {
   std::cerr << "Usage: " << std::endl;
   std::cerr << argv[0] << " inputImageFile" << std::endl;
   return EXIT_FAILURE;
   }

 double var = 5.0;
 if (argc > 2)
   {
   var = atof(argv[2]);
   }

   // Parse command line arguments
 std::string inputFilename = argv[1];

 // Setup types
 typedef itk::Image< float,  2 >                 FloatImageType;
 typedef itk::ImageFileReader< FloatImageType >  ReaderType;

 typedef itk::ZeroCrossingBasedEdgeDetectionImageFilter<
   FloatImageType, FloatImageType >  FilterType;

 // Create and setup a reader
 ReaderType::Pointer reader = ReaderType::New();
 reader->SetFileName( inputFilename.c_str() );

 // Create and setup a derivative filter
 FilterType::Pointer edgeDetector = FilterType::New();
 edgeDetector->SetInput( reader->GetOutput() );
 FilterType::ArrayType variance;
 variance.Fill(var);
 edgeDetector->SetVariance(variance);

 QuickView viewer;
 viewer.AddImage(
   reader->GetOutput(),true,
   itksys::SystemTools::GetFilenameName(inputFilename));  

 std::stringstream desc;
 desc << "ZeroBasedEdgeDetection, variance = "
      << edgeDetector->GetVariance();
 viewer.AddImage(
   edgeDetector->GetOutput(),
   true,
   desc.str());  

 viewer.Visualize();

 return EXIT_SUCCESS;

} </source>

CMakeLists.txt

<syntaxhighlight lang="cmake"> cmake_minimum_required(VERSION 3.9.5)

project(ZeroCrossingBasedEdgeDetectionImageFilter)

find_package(ITK REQUIRED) include(${ITK_USE_FILE}) if (ITKVtkGlue_LOADED)

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

else()

 find_package(ItkVtkGlue REQUIRED)
 include(${ItkVtkGlue_USE_FILE})
 set(Glue ItkVtkGlue)

endif()

add_executable(ZeroCrossingBasedEdgeDetectionImageFilter MACOSX_BUNDLE ZeroCrossingBasedEdgeDetectionImageFilter.cxx) target_link_libraries(ZeroCrossingBasedEdgeDetectionImageFilter

 ${Glue}  ${VTK_LIBRARIES} ${ITK_LIBRARIES})

</syntaxhighlight>

Download and Build ZeroCrossingBasedEdgeDetectionImageFilter

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

cd ZeroCrossingBasedEdgeDetectionImageFilter/build 

• If ITK is installed:

cmake ..

• If ITK is not installed but compiled on your system, you will need to specify the path to your ITK build:

cmake -DITK_DIR:PATH=/home/me/itk_build ..

Build the project,

make

and run it:

./ZeroCrossingBasedEdgeDetectionImageFilter

WINDOWS USERS PLEASE NOTE: Be sure to add the VTK and ITK bin directories to your path. This will resolve the VTK and ITK dll's at run time.

Building All of the Examples

Many of the examples in the ITK Wiki Examples Collection require VTK. You can build all of the the examples by following these instructions. If you are a new VTK user, you may want to try the Superbuild which will build a proper ITK and VTK.

ItkVtkGlue

ITK >= 4

For examples that use QuickView (which depends on VTK), you must have built ITK with Module_ITKVtkGlue=ON.

ITK < 4

Some of the ITK Examples require VTK to display the images. If you download the entire ITK Wiki Examples Collection, the ItkVtkGlue directory will be included and configured. If you wish to just build a few examples, then you will need to download ItkVtkGlue and build it. When you run cmake it will ask you to specify the location of the ItkVtkGlue binary directory.