ITK/Examples/ImageProcessing/AbsImageFilter

This example demonstrates how to compute the absolute value of each pixel in an image. The output shows the input image and the absolute value image. The input image, by necessity of this demonstration, has negative pixel values. This type of image is impossible to display directly, so it is scaled and shifted before being displayed so its values are in the range (0,255).

AbsImageFilter.cxx

<source lang="cpp">

1. include "itkImage.h"
2. include "itkImageFileWriter.h"
3. include "itkRescaleIntensityImageFilter.h"
4. include "itkAbsImageFilter.h"

1. include "QuickView.h"

typedef itk::Image<unsigned char, 2> UnsignedCharImageType; typedef itk::Image<float, 2> FloatImageType;

static void CreateImage(FloatImageType::Pointer image);

int main(int, char *[]) {

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

 // Take the absolute value of the image
 typedef itk::AbsImageFilter <FloatImageType, FloatImageType>
         AbsImageFilterType;

 AbsImageFilterType::Pointer absFilter
         = AbsImageFilterType::New ();
 absFilter->SetInput(image);

 QuickView viewer;
 viewer.AddImage<FloatImageType>(image);
 viewer.AddImage<FloatImageType>(absFilter->GetOutput());
 viewer.Visualize();

 return EXIT_SUCCESS;

}

void CreateImage(FloatImageType::Pointer image) {

 // Create an image with negative values
 FloatImageType::RegionType region;
 FloatImageType::IndexType start;
 start[0] = 0;
 start[1] = 0;

 FloatImageType::SizeType size;
 size[0] = 200;
 size[1] = 300;

 region.SetSize(size);
 region.SetIndex(start);

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

 itk::ImageRegionIterator<FloatImageType> imageIterator(image,region);

 while(!imageIterator.IsAtEnd())
   {
   imageIterator.Set(imageIterator.GetIndex()[0] - imageIterator.GetIndex()[1]);
   ++imageIterator;
   }
 

} </source>

CMakeLists.txt

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

project(AbsImageFilter)

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(AbsImageFilter MACOSX_BUNDLE AbsImageFilter.cxx) target_link_libraries(AbsImageFilter

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

</syntaxhighlight>

Download and Build AbsImageFilter

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

cd AbsImageFilter/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:

./AbsImageFilter

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.