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| ==Upsampling.cxx== | | {{warning|1=The media wiki content on this page is no longer maintained. The examples presented on the https://itk.org/Wiki/* pages likely require ITK version 4.13 or earlier releases. In many cases, the examples on this page no longer conform to the best practices for modern ITK versions. |
| <source lang="cpp">
| | }} |
| /**
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| \file Upsampling.cxx
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| \date 15 april 2011
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| \author Francis Girard
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| A simple example showing how to use the ResampleImageFilter and the
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| BSplineInterpolateImageFunction to (up)scale an image using bicubic
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| interpolation.
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| */
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|
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| #include "itkImage.h"
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| #include "itkImageFileReader.h"
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| #include "itkImageFileWriter.h"
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| #include "itkIdentityTransform.h"
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| #include "itkBSplineInterpolateImageFunction.h"
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| #include "itkResampleImageFilter.h"
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|
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| #include <iostream>
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|
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| int main( int argc, char * argv[] )
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| {
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| if( argc != 5 )
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| {
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| std::cerr << "Usage: "
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| << std::endl
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| << argv[0]
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| << " inputImageFile outputImageFile nNewWidth nNewHeight"
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| << std::endl;
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|
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| return EXIT_FAILURE;
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| }
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|
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| // Typedef's for pixel, image, reader and writer types
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| typedef unsigned char T_InputPixel;
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|
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| // Doesn't work for RGB pixels
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| //typedef unsigned char T_OutputPixel;
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| //typedef itk::CovariantVector<unsigned char, 3> T_InputPixel;
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| //typedef itk::CovariantVector<unsigned char, 3> T_OutputPixel;
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| typedef itk::Image<T_InputPixel, 2> T_Image; | |
| typedef itk::ImageFileReader<T_Image> T_Reader;
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|
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| typedef unsigned char T_WritePixel;
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| typedef itk::Image<T_WritePixel, 2> T_WriteImage;
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| typedef itk::ImageFileWriter<T_WriteImage> T_Writer;
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|
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| // Typedefs for the different (numerous!) elements of the "resampling"
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|
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| // Identity transform.
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| // We don't want any transform on our image except rescaling which is not
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| // specified by a transform but by the input/output spacing as we will see
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| // later.
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| // So no transform will be specified.
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| typedef itk::IdentityTransform<double, 2>
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| T_Transform;
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|
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| // If ITK resampler determines there is something to interpolate which is
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| // usually the case when upscaling (!) then we must specify the interpolation
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| // algorithm. In our case, we want bicubic interpolation. One way to implement
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| // it is with a third order b-spline. So the type is specified here and the
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| // order will be specified with a method call later on.
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| typedef itk::BSplineInterpolateImageFunction<T_Image, double, double>
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| T_Interpolator;
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|
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| // The resampler type itself.
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| typedef itk::ResampleImageFilter<T_Image, T_Image>
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| T_ResampleFilter;
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|
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|
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|
| // Prepare the reader and update it right away to know the sizes beforehand.
| | [https://itk.org/ITKExamples[ITK Sphinx Examples]] |
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| T_Reader::Pointer pReader = T_Reader::New();
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| pReader->SetFileName( argv[1] );
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| pReader->Update();
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|
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| // Prepare the resampler.
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|
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| // Instantiate the transform and specify it should be the id transform.
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| T_Transform::Pointer _pTransform = T_Transform::New();
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| _pTransform->SetIdentity();
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|
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| // Instantiate the b-spline interpolator and set it as the third order
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| // for bicubic.
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| T_Interpolator::Pointer _pInterpolator = T_Interpolator::New();
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| _pInterpolator->SetSplineOrder(3);
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|
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| // Instantiate the resampler. Wire in the transform and the interpolator.
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| T_ResampleFilter::Pointer _pResizeFilter = T_ResampleFilter::New();
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| _pResizeFilter->SetTransform(_pTransform);
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| _pResizeFilter->SetInterpolator(_pInterpolator);
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|
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| // Set the output origin. You may shift the original image "inside" the
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| // new image size by specifying something else than 0.0, 0.0 here.
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| | |
| const double vfOutputOrigin[2] = { 0.0, 0.0 };
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| _pResizeFilter->SetOutputOrigin(vfOutputOrigin);
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|
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| // Compute and set the output spacing
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| // Compute the output spacing from input spacing and old and new sizes.
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| //
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| // The computation must be so that the following holds:
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| //
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| // new width old x spacing
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| // ---------- = ---------------
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| // old width new x spacing
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| //
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| //
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| // new height old y spacing
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| // ------------ = ---------------
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| // old height new y spacing
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| //
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| // So either we specify new height and width and compute new spacings (as
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| // we do here) or we specify new spacing and compute new height and width
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| // and computations that follows need to be modified a little (as it is
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| // done at step 2 there:
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| // http://itk.org/Wiki/ITK/Examples/DICOM/ResampleDICOM)
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| //
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| unsigned int nNewWidth = atoi(argv[3]);
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| unsigned int nNewHeight = atoi(argv[4]);
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|
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| // Fetch original image size.
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| const T_Image::RegionType& inputRegion =
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| pReader->GetOutput()->GetLargestPossibleRegion();
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| const T_Image::SizeType& vnInputSize = inputRegion.GetSize();
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| unsigned int nOldWidth = vnInputSize[0];
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| unsigned int nOldHeight = vnInputSize[1];
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|
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| // Fetch original image spacing.
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| const T_Image::SpacingType& vfInputSpacing =
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| pReader->GetOutput()->GetSpacing();
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| // Will be {1.0, 1.0} in the usual
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| // case.
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|
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| double vfOutputSpacing[2];
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| vfOutputSpacing[0] = vfInputSpacing[0] * (double) nOldWidth / (double) nNewWidth;
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| vfOutputSpacing[1] = vfInputSpacing[1] * (double) nOldHeight / (double) nNewHeight;
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|
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| // Set the output spacing. If you comment out the following line, the original
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| // image will be simply put in the upper left corner of the new image without
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| // any scaling.
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| _pResizeFilter->SetOutputSpacing(vfOutputSpacing);
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|
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| // Set the output size as specified on the command line.
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| itk::Size<2> vnOutputSize = { {nNewWidth, nNewHeight} };
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| _pResizeFilter->SetSize(vnOutputSize);
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|
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| // Specify the input.
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| _pResizeFilter->SetInput(pReader->GetOutput());
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|
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| // Write the result
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| T_Writer::Pointer pWriter = T_Writer::New();
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| pWriter->SetFileName(argv[2]);
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| pWriter->SetInput(_pResizeFilter->GetOutput());
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| pWriter->Update();
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|
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| return EXIT_SUCCESS;
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| }
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| </source>
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| {{ITKCMakeLists|{{SUBPAGENAME}}}}
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