ITK/Examples/Developer/ImageFilter

This example demonstrates how to write a filter that produces an output image that is equal to the input image except its corner pixel is set to 3. The image that is the input to the filter remains unchanged.

ImageFilterExample.cxx

<source lang="cpp">

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

1. include "ImageFilter.h"

template <typename TImage> static void CreateImage(TImage* const image);

int main(int, char*[]) {

 // Setup types
 typedef itk::Image<int, 2>   ImageType;
 typedef itk::ImageFilter<ImageType>  FilterType;

 ImageType::Pointer image = ImageType::New();
 CreateImage(image.GetPointer());

 // Create and the filter
 FilterType::Pointer filter = FilterType::New();
 filter->SetInput(image);
 filter->Update();

 itk::Index<2> cornerPixel = image->GetLargestPossibleRegion().GetIndex();

 // The output here is:
 // 0
 // 3
 // That is, the filter changed the pixel, but the input remained unchagned.
 std::cout << image->GetPixel(cornerPixel) << std::endl;
 std::cout << filter->GetOutput()->GetPixel(cornerPixel) << std::endl;

 return EXIT_SUCCESS;

}

template <typename TImage> void CreateImage(TImage* const image) {

 // Create an image with 2 connected components
 typename TImage::IndexType corner = Template:0,0;

 unsigned int NumRows = 200;
 unsigned int NumCols = 300;
 typename TImage::SizeType size = Template:NumRows, NumCols;

 typename TImage::RegionType region(corner, size);

 image->SetRegions(region);
 image->Allocate();

 image->FillBuffer(0);

}

</source>

ImageFilter.h

<source lang="cpp">

1. ifndef __itkImageFilter_h
2. define __itkImageFilter_h

1. include "itkImageToImageFilter.h"

namespace itk { template< class TImage> class ImageFilter:public ImageToImageFilter< TImage, TImage > { public:

 /** Standard class typedefs. */
 typedef ImageFilter             Self;
 typedef ImageToImageFilter< TImage, TImage > Superclass;
 typedef SmartPointer< Self >        Pointer;

 /** Method for creation through the object factory. */
 itkNewMacro(Self);

 /** Run-time type information (and related methods). */
 itkTypeMacro(ImageFilter, ImageToImageFilter);

protected:

 ImageFilter(){}
 ~ImageFilter(){}

 /** Does the real work. */
 virtual void GenerateData();

private:

 ImageFilter(const Self &); //purposely not implemented
 void operator=(const Self &);  //purposely not implemented

}; } //namespace ITK

1. ifndef ITK_MANUAL_INSTANTIATION
2. include "ImageFilter.hxx"
3. endif

1. endif // __itkImageFilter_h

</source>

ImageFilter.hxx

<source lang="cpp">

1. ifndef __itkImageFilter_hxx
2. define __itkImageFilter_hxx

1. include "ImageFilter.h"
2. include "itkObjectFactory.h"
3. include "itkImageRegionIterator.h"
4. include "itkImageRegionConstIterator.h"

namespace itk {

template< class TImage> void ImageFilter< TImage>

GenerateData()

{

 typename TImage::ConstPointer input = this->GetInput();
 typename TImage::Pointer output = this->GetOutput();

 itk::Index<2> cornerPixel = input->GetLargestPossibleRegion().GetIndex();
 typename TImage::PixelType newValue = 3;

 this->AllocateOutputs();

 ImageAlgorithm::Copy(input.GetPointer(), output.GetPointer(), output->GetRequestedRegion(),
                      output->GetRequestedRegion() );

 output->SetPixel( cornerPixel, newValue );

}

}// end namespace

1. endif

</source>

CMakeLists.txt

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

project(ImageFilter)

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

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

endif()

add_executable(ImageFilter MACOSX_BUNDLE ImageFilter.cxx)

if( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(ImageFilter ITKReview ${ITK_LIBRARIES})

else( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(ImageFilter ${ITK_LIBRARIES})

endif( "${ITK_VERSION_MAJOR}" LESS 4 )

</syntaxhighlight>

Download and Build ImageFilter

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

cd ImageFilter/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:

./ImageFilter

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.