ITK/Examples/ImageProcessing/NthElementImageAdaptor

This example demonstrates how to access a specified channel of a vector image as if it were a scalar image. This does NOT work for itk::VectorImage.

NthElementImageAdaptor.cxx

<source lang="cpp">

1. include "itkImageAdaptor.h"
2. include "itkImageRegionIterator.h"
3. include "itkNthElementImageAdaptor.h"

typedef itk::Image<itk::CovariantVector< float, 3>, 2> VectorImageType;

static void CreateImage(VectorImageType::Pointer image);

int main(int, char *[]) {

 VectorImageType::Pointer image = VectorImageType::New();
 CreateImage(image);

 itk::Index<2> index;
 index.Fill(0);

 std::cout << image->GetPixel(index) << std::endl;

 typedef itk::NthElementImageAdaptor<VectorImageType,
   float> ImageAdaptorType;

 ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();

 adaptor->SelectNthElement(0);
 adaptor->SetImage(image);

 std::cout << adaptor->GetPixel(index) << std::endl;

 return EXIT_SUCCESS;

}

void CreateImage(VectorImageType::Pointer image) {

 VectorImageType::IndexType start;
 start.Fill(0);

 VectorImageType::SizeType size;
 size.Fill(2);

 VectorImageType::RegionType region;
 region.SetSize(size);
 region.SetIndex(start);

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

 // Create a pixel and fill it with (1,2,3), and set every pixel of the image to this pixel.

 itk::ImageRegionIterator<VectorImageType> imageIterator(image,image->GetLargestPossibleRegion());
 itk::CovariantVector<float, 3> vectorPixel;
 vectorPixel[0] = 1;
 vectorPixel[1] = 2;
 vectorPixel[2] = 3;

 image->FillBuffer(vectorPixel);

} </source>

CMakeLists.txt

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

project(NthElementImageAdaptor)

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

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

endif()

add_executable(NthElementImageAdaptor MACOSX_BUNDLE NthElementImageAdaptor.cxx)

if( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(NthElementImageAdaptor ITKReview ${ITK_LIBRARIES})

else( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(NthElementImageAdaptor ${ITK_LIBRARIES})

endif( "${ITK_VERSION_MAJOR}" LESS 4 )

</syntaxhighlight>

Download and Build NthElementImageAdaptor

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

cd NthElementImageAdaptor/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:

./NthElementImageAdaptor

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.