ITK/Examples/ImageProcessing/ScaleTransform

In this example, we demonstrate the itkScaleTransform. By specifying the scale as 1.5, what we are actually doing is making the new image bigger than the old image in the physical space. When the image is resampled, the outer regions of the image are not overlapping the old image. Therefore, the resulting image appears to have shrunk, even though the scale factor was > 1.

ScaleTransform.cxx

<source lang="cpp">

1. include "itkImage.h"
2. include "itkScaleTransform.h"
3. include "itkImageFileReader.h"
4. include "itkImageFileWriter.h"
5. include "itkResampleImageFilter.h"

typedef itk::Image<unsigned char, 2> ImageType;

static void CreateImage(ImageType::Pointer image);

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

 ImageType::Pointer image = ImageType::New();
 CreateImage(image);
 
 typedef  itk::ImageFileWriter<ImageType> WriterType;
 WriterType::Pointer inputWriter = WriterType::New();
 inputWriter->SetFileName("input.png");
 inputWriter->SetInput(image);
 inputWriter->Update();

 // typedef itk::ScaleTransform<float, 2> TransformType; // If you want to use float here, you must use:
 // typedef itk::ResampleImageFilter<ImageType, ImageType, float> ResampleImageFilterType; later.
 typedef itk::ScaleTransform<double, 2> TransformType;
 TransformType::Pointer scaleTransform = TransformType::New();
 itk::FixedArray<float, 2> scale;
 scale[0] = 1.5; // newWidth/oldWidth
 scale[1] = 1.5;
 scaleTransform->SetScale(scale);

 itk::Point<float,2> center;
 center[0] = image->GetLargestPossibleRegion().GetSize()[0]/2;
 center[1] = image->GetLargestPossibleRegion().GetSize()[1]/2;

 scaleTransform->SetCenter(center);

 typedef itk::ResampleImageFilter<ImageType, ImageType> ResampleImageFilterType;
 ResampleImageFilterType::Pointer resampleFilter = ResampleImageFilterType::New();
 resampleFilter->SetTransform(scaleTransform);
 resampleFilter->SetInput(image);
 resampleFilter->SetSize(image->GetLargestPossibleRegion().GetSize());
 resampleFilter->Update();

 WriterType::Pointer outputWriter = WriterType::New();
 outputWriter->SetFileName("output.png");
 outputWriter->SetInput(resampleFilter->GetOutput());
 outputWriter->Update();

 return EXIT_SUCCESS;

}

void CreateImage(ImageType::Pointer image) {

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

 itk::Size<2> size;
 size.Fill(101);

 ImageType::RegionType region(start, size);
 image->SetRegions(region);
 image->Allocate();
 image->FillBuffer(0);

 // Make a white square
 for(unsigned int r = 40; r < 60; r++)
   {
   for(unsigned int c = 40; c < 60; c++)
     {
     ImageType::IndexType pixelIndex;
     pixelIndex[0] = r;
     pixelIndex[1] = c;

     image->SetPixel(pixelIndex, 255);
     }
   }

 itk::ImageRegionIterator<ImageType> imageIterator(image, image->GetLargestPossibleRegion());

 // Draw a white border
 while(!imageIterator.IsAtEnd())
   {
   if(imageIterator.GetIndex()[0] == 0 || imageIterator.GetIndex()[0] == static_cast<int>(image->GetLargestPossibleRegion().GetSize()[0]) - 1 ||
      imageIterator.GetIndex()[1] == 0 || imageIterator.GetIndex()[1] == static_cast<int>(image->GetLargestPossibleRegion().GetSize()[1]) - 1)
     {
     imageIterator.Set(255);
     }
   ++imageIterator;
   }

}

</source>

CMakeLists.txt

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

project(ScaleTransform)

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

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

endif()

add_executable(ScaleTransform MACOSX_BUNDLE ScaleTransform.cxx)

if( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(ScaleTransform ITKReview ${ITK_LIBRARIES})

else( "${ITK_VERSION_MAJOR}" LESS 4 )

 target_link_libraries(ScaleTransform ${ITK_LIBRARIES})

endif( "${ITK_VERSION_MAJOR}" LESS 4 )

</syntaxhighlight>

Download and Build ScaleTransform

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

cd ScaleTransform/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:

./ScaleTransform

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.