ITK/Examples/EdgesAndGradients/GradientRecursiveGaussianImageFilter

This example demonstrates how to use the GradientRecursiveGaussianImageFilter which computes the gradient of an image by convolution with the first derivative of a Gaussian. The filter is implemented using the RecursiveGaussianImageFilter.

GradientRecursiveGaussianImageFilter.cxx

<source lang="cpp">

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

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

  // Verify number of parameters in command line
 if( argc < 3 )
   {
   std::cerr << "Usage: " << std::endl;
   std::cerr << argv[0] << " inputImageFile  outputVectorImageFile " << std::endl;
   return EXIT_FAILURE;
   }

 //typedef
 typedef signed short          InputPixelType;
 typedef float                 ComponentType;
 const   unsigned int          Dimension = 2;

 typedef itk::CovariantVector< ComponentType, 

Dimension > OutputPixelType;

 typedef itk::Image< InputPixelType,  Dimension >    InputImageType;
 typedef itk::Image< OutputPixelType, Dimension >    OutputImageType;

 typedef itk::ImageFileReader< InputImageType  >  ReaderType;
 typedef itk::ImageFileWriter< OutputImageType >  WriterType;

 //Filter class is instantiated
 typedef itk::GradientRecursiveGaussianImageFilter<InputImageType, OutputImageType> FilterType;

 FilterType::Pointer filter = FilterType::New();

 //sigma is specified in millimeters
 filter->SetSigma( 1.5 );  

 //create the reader and writer 
 ReaderType::Pointer reader = ReaderType::New();
 WriterType::Pointer writer = WriterType::New();

 //recover file names from command line arguments
 const char * inputFilename  = argv[1];
 const char * outputFilename = argv[2];		//e.g. *.mhd (can be displayed in Paraview)

 reader->SetFileName( inputFilename  );
 writer->SetFileName(outputFilename);

 //  processing pipeline:
 filter->SetInput( reader->GetOutput() );
 writer->SetInput( filter->GetOutput() );

 try 
   { 
   //execute the pipeline
   writer->Update(); 
   } 
 catch( itk::ExceptionObject & err ) 
   { 
   std::cerr << "ExceptionObject caught !" << std::endl; 
   std::cerr << err << std::endl; 
   return EXIT_FAILURE;
   } 

 return EXIT_SUCCESS;

} </source>

CMakeLists.txt

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

project(GradientRecursiveGaussianImageFilter)

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

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

endif()

add_executable(GradientRecursiveGaussianImageFilter MACOSX_BUNDLE GradientRecursiveGaussianImageFilter.cxx)

if( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(GradientRecursiveGaussianImageFilter ITKReview ${ITK_LIBRARIES})

else( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(GradientRecursiveGaussianImageFilter ${ITK_LIBRARIES})

endif( "${ITK_VERSION_MAJOR}" LESS 4 )

</syntaxhighlight>

Download and Build GradientRecursiveGaussianImageFilter

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

cd GradientRecursiveGaussianImageFilter/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:

./GradientRecursiveGaussianImageFilter

WINDOWS USERS PLEASE NOTE: Be sure to add the ITK bin directory to your path. This will resolve the 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.