ImageRegionIteratorWithIndex.cxx

For a complete description of the ITK Image Iterators and their API, please see the Iterators chapter in the ITK Software Guide. The ITK Software Guide is available in print and as a free .pdf download from http://www.itk.org.

See Also

ImageConstIterator

ConditionalConstIterator

ConstNeighborhoodIterator

ConstShapedNeighborhoodIterator

ConstSliceIterator

CorrespondenceDataStructureIterator

FloodFilledFunctionConditionalConstIterator

FloodFilledImageFunctionConditionalConstIterator

FloodFilledImageFunctionConditionalIterator

FloodFilledSpatialFunctionConditionalConstIterator

FloodFilledSpatialFunctionConditionalIterator

ImageConstIterator

ImageConstIteratorWithIndex

ImageIterator

ImageIteratorWithIndex

ImageLinearConstIteratorWithIndex

ImageLinearIteratorWithIndex

ImageRandomConstIteratorWithIndex

ImageRandomIteratorWithIndex

ImageRegionConstIterator

ImageRegionConstIteratorWithIndex

ImageRegionExclusionConstIteratorWithIndex

ImageRegionExclusionIteratorWithIndex

ImageRegionIterator

ImageRegionIteratorWithIndex

ImageRegionReverseConstIterator

ImageRegionReverseIterator

ImageReverseConstIterator

ImageReverseIterator

ImageSliceConstIteratorWithIndex

ImageSliceIteratorWithIndex

NeighborhoodIterator

PathConstIterator

PathIterator

ShapedNeighborhoodIterator

SliceIterator

ImageConstIteratorWithIndex

/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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
 *
 *         http://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 : 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
#include "itkImageRegionIteratorWithIndex.h"
// Software Guide : EndCodeSnippet
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"

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 -1;
    }

  // 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
  const unsigned int Dimension = 2;

  typedef itk::RGBPixel< unsigned char >        RGBPixelType;
  typedef itk::Image< RGBPixelType, Dimension > ImageType;

  typedef itk::ImageRegionIteratorWithIndex< ImageType > IteratorType;
  // Software Guide : EndCodeSnippet

  typedef itk::ImageFileReader< ImageType > ReaderType;
  typedef itk::ImageFileWriter< ImageType > WriterType;

  ImageType::ConstPointer inputImage;
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName( argv[1] );
  try
    {
    reader->Update();
    inputImage = reader->GetOutput();
    }
  catch ( itk::ExceptionObject &err)
    {
    std::cout << "ExceptionObject caught !" << std::endl;
    std::cout << err << std::endl;
    return -1;
    }

  // 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 ( itk::ExceptionObject &err)
    {
    std::cout << "ExceptionObject caught !" << std::endl;
    std::cout << err << std::endl;
    return -1;
}

  // 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 0;
}