ImageAdaptor1.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 : BeginLatex
//
//This example illustrates how the \doxygen{itk}{ImageAdaptor} can be used to cast
// an image from one pixel type to another. In particular, we will
// \emph{adapt} an \code{unsigned char} image to make it appear as an image of
// pixel type \code{float}.
//
// \index{itk::ImageAdaptor!Instantiation}
// \index{itk::ImageAdaptor!Header}
//
// We begin by including the relevant headers.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
#include "otbImage.h"
#include "itkImageAdaptor.h"
// Software Guide : EndCodeSnippet

#include "itkImageRegionIteratorWithIndex.h"
#include "otbImageFileReader.h"

//  Software Guide : BeginLatex
//
// First, we need to define a \emph{pixel accessor} class that does the actual
// conversion. Note that in general, the only valid operations for pixel
// accessors are those that only require the value of the input pixel. As
// such, neighborhood type operations are not possible. A pixel accessor must
// provide methods \code{Set()} and \code{Get()}, and define the types of
// \code{InternalPixelType} and \code{ExternalPixelType}. The
// \code{InternalPixelType} corresponds to the pixel type of the image to be
// adapted (\code{unsigned char} in this example). The \code{ExternalPixelType}
// corresponds to the pixel type we wish to emulate with the ImageAdaptor
// (\code{float} in this case).
//
//  Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
class CastPixelAccessor
{
public:
  typedef unsigned char InternalType;
  typedef float         ExternalType;

  static void Set(InternalType& output, const ExternalType& input)
  {
    output = static_cast<InternalType>(input);
  }

  static ExternalType Get(const InternalType& input)
  {
    return static_cast<ExternalType>(input);
  }
};
// Software Guide : EndCodeSnippet

//-------------------------
//
//   Main code
//
//-------------------------

int main(int argc, char *argv[])
{
  if (argc < 2)
    {
    std::cerr << "Usage: " << std::endl;
    std::cerr << "ImageAdaptor1   inputFileName" << std::endl;
    return -1;
    }

//  Software Guide : BeginLatex
//
//  The CastPixelAccessor class simply applies a
//  \code{static\_cast} to the pixel values. We now use this pixel accessor
//  to define the image adaptor type and create an instance using
//  the standard \code{New()} method.
//
//  Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  typedef unsigned char InputPixelType;
  const unsigned int Dimension = 2;
  typedef otb::Image<InputPixelType, Dimension> ImageType;

  typedef itk::ImageAdaptor<ImageType, CastPixelAccessor> ImageAdaptorType;
  ImageAdaptorType::Pointer adaptor = ImageAdaptorType::New();
// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex
//
// We also create an image reader templated over the input image type and
// read the input image from file.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  typedef otb::ImageFileReader<ImageType> ReaderType;
  ReaderType::Pointer reader = ReaderType::New();
// Software Guide : EndCodeSnippet

  reader->SetFileName(argv[1]);
  reader->Update();

//  Software Guide : BeginLatex
//
//  The output of the reader is then connected as the input to the image
//  adaptor.
//
//  Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  adaptor->SetImage(reader->GetOutput());
// Software Guide : EndCodeSnippet

//  Software Guide : BeginLatex
//
//  In the following code, we visit the image using an iterator
//  instantiated using the adapted image type and compute the
//  sum of the pixel values.
//
//  Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  typedef itk::ImageRegionIteratorWithIndex<ImageAdaptorType> IteratorType;
  IteratorType it(adaptor, adaptor->GetBufferedRegion());

  double sum = 0.0;
  it.GoToBegin();
  while (!it.IsAtEnd())
    {
    float value = it.Get();
    sum += value;
    ++it;
    }
// Software Guide : EndCodeSnippet

  std::cout << "Sum of pixels is: " << sum << std::endl;

//  Software Guide : BeginLatex
//
// Although in this example, we are just performing a simple summation, the key
// concept is that access to pixels is performed as if the pixel is of type
//  \code{float}. Additionally, it should be noted that the adaptor is used
// as if it was an actual image and not as a filter. ImageAdaptors conform
// to the same API as the  \doxygen{otb}{Image} class.
//
//  Software Guide : EndLatex

  return EXIT_SUCCESS;
}