ImageRegionIterator.cxx

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/*=========================================================================

  Program:   ORFEO Toolbox
  Language:  C++
  Date:      $Date$
  Version:   $Revision$


  Copyright (c) Centre National d'Etudes Spatiales. All rights reserved.
  See OTBCopyright.txt for details.


     This software is distributed WITHOUT ANY WARRANTY; without even
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/

//  Software Guide : BeginCommandLineArgs
//     INPUTS: {QB_Suburb.png}
//     OUTPUTS: {ImageRegionIteratorOutput.png}
//     10 10 110 140
//  Software Guide : EndCommandLineArgs

// Software Guide : BeginLatex
//
// \index{Iterators!speed}
// The \doxygen{itk}{ImageRegionIterator} is optimized for
// iteration speed and is the first choice for iterative, pixel-wise operations
// when location in the image is not
// important. ImageRegionIterator is the least specialized of the ITK
// image iterator classes.  It implements all of the methods described in the
// preceding section.
//
// The following example illustrates the use of
// \doxygen{itk}{ImageRegionConstIterator} and ImageRegionIterator.
// Most of the code constructs introduced apply to other ITK iterators as
// well. This simple application crops a subregion from an image by copying
// its pixel values into to a second, smaller image.
//
// \index{Iterators!and image regions}
// \index{itk::ImageRegionIterator!example of using|(}
// We begin by including the appropriate header files.
// Software Guide : EndLatex

#include "otbImage.h"
// Software Guide : BeginCodeSnippet
#include "itkImageRegionConstIterator.h"
#include "itkImageRegionIterator.h"
// Software Guide : EndCodeSnippet
#include "otbImageFileReader.h"
#include "otbImageFileWriter.h"

int main(int argc, char *argv[])
{
  // Verify the number of parameters on the command line.
  if (argc < 7)
    {
    std::cerr << "Missing parameters. " << std::endl;
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0]
              << " inputImageFile outputImageFile startX startY sizeX sizeY"
              << std::endl;
    return -1;
    }

// Software Guide : BeginLatex
//
// Next we define a pixel type and corresponding image type. ITK iterator
// classes expect the image type as their template parameter.
//
// Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  const unsigned int Dimension = 2;

  typedef unsigned char                    PixelType;
  typedef otb::Image<PixelType, Dimension> ImageType;

  typedef itk::ImageRegionConstIterator<ImageType> ConstIteratorType;
  typedef itk::ImageRegionIterator<ImageType>      IteratorType;
  // Software Guide : EndCodeSnippet

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

// Software Guide : BeginLatex
//
// Information about the subregion to copy is read from the command line. The
// subregion is defined by an \doxygen{itk}{ImageRegion} object, with a starting
// grid index and a size (Section~\ref{sec:ImageSection}).
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  ImageType::RegionType inputRegion;

  ImageType::RegionType::IndexType inputStart;
  ImageType::RegionType::SizeType  size;

  inputStart[0] = ::atoi(argv[3]);
  inputStart[1] = ::atoi(argv[4]);

  size[0]  = ::atoi(argv[5]);
  size[1]  = ::atoi(argv[6]);

  inputRegion.SetSize(size);
  inputRegion.SetIndex(inputStart);
// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex
//
// The destination region in the output image is defined using the input region
// size, but a different start index.  The starting index for the destination
// region is the corner of the newly generated image.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  ImageType::RegionType outputRegion;

  ImageType::RegionType::IndexType outputStart;

  outputStart[0] = 0;
  outputStart[1] = 0;

  outputRegion.SetSize(size);
  outputRegion.SetIndex(outputStart);
// Software Guide : EndCodeSnippet

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

  // Check that the region is contained within the input image.
  if (!reader->GetOutput()->GetRequestedRegion().IsInside(inputRegion))
    {
    std::cerr << "Error" << std::endl;
    std::cerr << "The region " << inputRegion <<
    "is not contained within the input image region "
              << reader->GetOutput()->GetRequestedRegion() << std::endl;
    return -1;
    }

// Software Guide : BeginLatex
//
// After reading the input image and checking that the desired subregion is,
// in fact, contained in the input, we allocate an output image.  It is
// fundamental to set valid values to some of the basic image information
// during the copying process.
// In particular, the starting index of the output region
// is now filled up with zero values and the coordinates of the physical
// origin are computed as a shift from the origin of the input image. This is
// quite important since it will allow us to later
// register the extracted region against the original image.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  ImageType::Pointer outputImage = ImageType::New();
  outputImage->SetRegions(outputRegion);
  const ImageType::SpacingType& spacing = reader->GetOutput()->GetSpacing();
  const ImageType::PointType&   inputOrigin = reader->GetOutput()->GetOrigin();
  double                        outputOrigin[Dimension];

  for (unsigned int i = 0; i < Dimension; ++i)
    {
    outputOrigin[i] = inputOrigin[i] + spacing[i] * inputStart[i];
    }

  outputImage->SetSpacing(spacing);
  outputImage->SetOrigin(outputOrigin);
  outputImage->Allocate();
// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex
//
// \index{Iterators!construction of} \index{Iterators!and image regions}
// The necessary images and region definitions are now in place.  All that is
// left to do is to create the iterators and perform the copy.  Note that image
// iterators are not accessed via smart pointers so they are light-weight
// objects that are instantiated on the stack.  Also notice how the input and
// output iterators are defined over the \emph{same corresponding region}.  Though the
// images are different sizes, they both contain the same target subregion.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  ConstIteratorType inputIt(reader->GetOutput(), inputRegion);
  IteratorType      outputIt(outputImage,         outputRegion);

  for (inputIt.GoToBegin(), outputIt.GoToBegin(); !inputIt.IsAtEnd();
       ++inputIt, ++outputIt)
    {
    outputIt.Set(inputIt.Get());
    }
// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex
//
// \index{Iterators!image dimensionality}
//  The \code{for} loop above is a common
// construct in ITK/OTB.  The beauty of these four lines of code is that they are
// equally valid for one, two, three, or even ten dimensional data, and no
// knowledge of the size of the image is necessary.  Consider the ugly
// alternative of ten nested \code{for} loops for traversing an image.
//
// Software Guide : EndLatex

  WriterType::Pointer writer = WriterType::New();
  writer->SetFileName(argv[2]);
  writer->SetInput(outputImage);

  try
    {
    writer->Update();
    }
  catch (itk::ExceptionObject& err)
    {
    std::cerr << "ExceptionObject caught !" << std::endl;
    std::cerr << err << std::endl;
    return -1;
    }

// Software Guide : BeginLatex
//
// Let's run this example on the image \code{QB\_Suburb.png} found
// in \code{Examples/Data}.  The command line arguments specify the
// input and output file names, then the $x$, $y$ origin and the $x$, $y$ size
// of the cropped subregion.
//
// \small
// \begin{verbatim}
// ImageRegionIterator QB_Suburb.png ImageRegionIteratorOutput.png 20 70 210 140
// \end{verbatim}
// \normalsize
//
// The output is the cropped subregion shown in
// Figure~\ref{fig:ImageRegionIteratorOutput}.
//
// \begin{figure}
// \centering
// \includegraphics[width=0.4\textwidth]{QB_Suburb.eps}
// \includegraphics[width=0.3\textwidth]{ImageRegionIteratorOutput.eps}
// \itkcaption[Copying an image subregion using ImageRegionIterator]{Cropping a
// region from an image.  The original image is shown at left.  The image on
// the right is the result of applying the ImageRegionIterator example code.}
// \protect\label{fig:ImageRegionIteratorOutput}
// \end{figure}
//
// \index{itk::ImageRegionIterator!example of using|)}
//
// Software Guide : EndLatex

  return EXIT_SUCCESS;
}