ITK  5.2.0
Insight Toolkit
Examples/Iterators/ImageRegionIteratorWithIndex.cxx
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* Licensed under the Apache License, Version 2.0 (the "License");
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// Software Guide : BeginCommandLineArgs
// INPUTS: {VisibleWomanEyeSlice.png}
// OUTPUTS: {ImageRegionIteratorWithIndexOutput.png}
// Software Guide : EndCommandLineArgs
// Software Guide : BeginLatex
//
// \index{Iterators!speed}
// The ``WithIndex'' family of iterators was designed for algorithms that
// use both the value and the location of image pixels in calculations. Unlike
// \doxygen{ImageRegionIterator}, which calculates an index only when
// asked for, \doxygen{ImageRegionIteratorWithIndex} maintains its
// index location as a member variable that is updated during the increment or
// decrement process. Iteration speed is penalized, but the index queries are
// more efficient.
//
// \index{itk::ImageRegionIteratorWithIndex!example of using|(}
//
// The following example illustrates the use of
// ImageRegionIteratorWithIndex. The algorithm mirrors
// a 2D image across its $x$-axis (see \doxygen{FlipImageFilter} for an ND
// version). The algorithm makes extensive use of the \code{GetIndex()}
// method.
//
// We start by including the proper header file.
//
// Software Guide : EndLatex
#include "itkImage.h"
#include "itkRGBPixel.h"
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
int
main(int argc, char * argv[])
{
// Verify the number of parameters on the command line.
if (argc < 3)
{
std::cerr << "Missing parameters. " << std::endl;
std::cerr << "Usage: " << std::endl;
std::cerr << argv[0] << " inputImageFile outputImageFile" << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// For this example, we will use an RGB pixel type so that we can process
// color images. Like most other ITK image iterator,
// ImageRegionIteratorWithIndex class expects the image type as its
// single template parameter.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
constexpr unsigned int Dimension = 2;
using RGBPixelType = itk::RGBPixel<unsigned char>;
// Software Guide : EndCodeSnippet
using ReaderType = itk::ImageFileReader<ImageType>;
using WriterType = itk::ImageFileWriter<ImageType>;
ImageType::ConstPointer inputImage;
ReaderType::Pointer reader = ReaderType::New();
reader->SetFileName(argv[1]);
try
{
reader->Update();
inputImage = reader->GetOutput();
}
catch (const itk::ExceptionObject & err)
{
std::cerr << "ExceptionObject caught !" << std::endl;
std::cerr << err << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// An \code{ImageType} smart pointer called \code{inputImage} points to the
// output of the image reader. After updating the image reader, we can
// allocate an output image of the same size, spacing, and origin as the
// input image.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
ImageType::Pointer outputImage = ImageType::New();
outputImage->SetRegions(inputImage->GetRequestedRegion());
outputImage->CopyInformation(inputImage);
outputImage->Allocate();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Next we create the iterator that walks the output image. This algorithm
// requires no iterator for the input image.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
IteratorType outputIt(outputImage, outputImage->GetRequestedRegion());
// Software Guide : EndCodeSnippet
// Software Guide: BeginLatex
//
// This axis flipping algorithm works by iterating through the output image,
// querying the iterator for its index, and copying the value from the input
// at an index mirrored across the $x$-axis.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
ImageType::IndexType requestedIndex =
outputImage->GetRequestedRegion().GetIndex();
ImageType::SizeType requestedSize =
outputImage->GetRequestedRegion().GetSize();
for (outputIt.GoToBegin(); !outputIt.IsAtEnd(); ++outputIt)
{
ImageType::IndexType idx = outputIt.GetIndex();
idx[0] = requestedIndex[0] + requestedSize[0] - 1 - idx[0];
outputIt.Set(inputImage->GetPixel(idx));
}
// Software Guide : EndCodeSnippet
WriterType::Pointer writer = WriterType::New();
writer->SetFileName(argv[2]);
writer->SetInput(outputImage);
try
{
writer->Update();
}
catch (const itk::ExceptionObject & err)
{
std::cerr << "ExceptionObject caught !" << std::endl;
std::cerr << err << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// Let's run this example on the image \code{VisibleWomanEyeSlice.png} found
// in the \code{Examples/Data} directory.
// Figure~\ref{fig:ImageRegionIteratorWithIndexExample} shows how the
// original image has been mirrored across its $x$-axis in the output.
//
// \begin{figure} \center
// \includegraphics[width=0.44\textwidth]{VisibleWomanEyeSlice}
// \includegraphics[width=0.44\textwidth]{ImageRegionIteratorWithIndexOutput}
// \itkcaption[Using the ImageRegionIteratorWithIndex]{Results of using
// ImageRegionIteratorWithIndex to mirror an image across an axis. The
// original image is shown at left. The mirrored output is shown at right.}
// \label{fig:ImageRegionIteratorWithIndexExample}
// \end{figure}
//
// \index{itk::ImageRegionIteratorWithIndex!example of using|)}
//
// Software Guide : EndLatex
return EXIT_SUCCESS;
}
itk::RGBPixel
Represent Red, Green and Blue components for color images.
Definition: itkRGBPixel.h:58
itkRGBPixel.h
itkImageFileReader.h
itk::GTest::TypedefsAndConstructors::Dimension2::SizeType
ImageBaseType::SizeType SizeType
Definition: itkGTestTypedefsAndConstructors.h:49
itkImage.h
itkImageRegionIteratorWithIndex.h
itk::ImageFileReader
Data source that reads image data from a single file.
Definition: itkImageFileReader.h:75
itk::GTest::TypedefsAndConstructors::Dimension2::IndexType
ImageBaseType::IndexType IndexType
Definition: itkGTestTypedefsAndConstructors.h:50
itk::ImageFileWriter
Writes image data to a single file.
Definition: itkImageFileWriter.h:87
itk::Index::GetIndex
const IndexValueType * GetIndex() const
Definition: itkIndex.h:228
itk::ImageRegionIteratorWithIndex
A multi-dimensional iterator templated over image type that walks pixels within a region and is speci...
Definition: itkImageRegionIteratorWithIndex.h:71
itkImageFileWriter.h
itk::Image
Templated n-dimensional image class.
Definition: itkImage.h:86
itk::GTest::TypedefsAndConstructors::Dimension2::Dimension
constexpr unsigned int Dimension
Definition: itkGTestTypedefsAndConstructors.h:44
itk::Size::GetSize
const SizeValueType * GetSize() const
Definition: itkSize.h:169