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/*=========================================================================
*
* Copyright NumFOCUS
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
// Software Guide : BeginLatex
//
// This example illustrates how to use the WarpImageFilter and a
// deformation field for resampling an image. This is typically done
// as the last step of a deformable registration algorithm.
//
// \index{itk::WarpImageFilter}
//
// Software Guide : EndLatex
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
// Software Guide : BeginCodeSnippet
#include "itkWarpImageFilter.h"
// Software Guide : EndCodeSnippet
int
main(int argc, char * argv[])
{
if (argc < 4)
{
std::cerr << "Usage: " << std::endl;
std::cerr << argv[0]
<< " inputImageFile inputDisplacementField outputImageFile"
<< std::endl;
return EXIT_FAILURE;
}
constexpr unsigned int Dimension = 2;
// Software Guide : BeginLatex
//
// The deformation field is represented as an image of vector pixel types.
// The dimension of the vectors is the same as the dimension of the input
// image. Each vector in the deformation field represents the distance
// between a geometric point in the input space and a point in the output
// space such that: \begin{equation} p_{in} = p_{out} + \text{distance}
// \end{equation}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using VectorComponentType = float;
using VectorPixelType = itk::Vector<VectorComponentType, Dimension>;
using DisplacementFieldType = itk::Image<VectorPixelType, Dimension>;
using PixelType = unsigned char;
using ImageType = itk::Image<PixelType, Dimension>;
// Software Guide : EndCodeSnippet
using ReaderType = itk::ImageFileReader<ImageType>;
using WriterType = itk::ImageFileWriter<ImageType>;
// Software Guide : BeginLatex
//
// The field is read from a file, through a reader instantiated over the
// vector pixel types.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using FieldReaderType = itk::ImageFileReader<DisplacementFieldType>;
// Software Guide : EndCodeSnippet
auto reader = ReaderType::New();
auto writer = WriterType::New();
reader->SetFileName(argv[1]);
writer->SetFileName(argv[3]);
// Software Guide : BeginCodeSnippet
auto fieldReader = FieldReaderType::New();
fieldReader->SetFileName(argv[2]);
fieldReader->Update();
DisplacementFieldType::ConstPointer deformationField =
fieldReader->GetOutput();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The \doxygen{WarpImageFilter} is templated over the input image type,
// output image type and the deformation field type.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using FilterType =
itk::WarpImageFilter<ImageType, ImageType, DisplacementFieldType>;
auto filter = FilterType::New();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Typically the mapped position does not correspond to an integer pixel
// position in the input image. Interpolation via an image function is used
// to compute values at non-integer positions. This is done via the
// \code{SetInterpolator()} method.
// \index{itk::Warp\-Image\-Filter!SetInterpolator()}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using InterpolatorType =
itk::LinearInterpolateImageFunction<ImageType, double>;
auto interpolator = InterpolatorType::New();
filter->SetInterpolator(interpolator);
// Software Guide : EndCodeSnippet
// SoftwareGuide : BeginLatex
//
// The output image spacing and origin may be set via SetOutputSpacing(),
// SetOutputOrigin(). This is taken from the deformation field.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->SetOutputSpacing(deformationField->GetSpacing());
filter->SetOutputOrigin(deformationField->GetOrigin());
filter->SetOutputDirection(deformationField->GetDirection());
filter->SetDisplacementField(deformationField);
// Software Guide : EndCodeSnippet
filter->SetInput(reader->GetOutput());
writer->SetInput(filter->GetOutput());
try
{
writer->Update();
}
catch (const itk::ExceptionObject & excp)
{
std::cerr << "Exception thrown " << std::endl;
std::cerr << excp << std::endl;
}
return EXIT_SUCCESS;
}
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