DataRepresentation/Image/Image2.cxx

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

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


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

  Some parts of this code are derived from ITK. See ITKCopyright.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.

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


#include "otbImage.h"

//  Software Guide : BeginLatex
//
//  The first thing required to read an image from a file is to include
//  the header file of the \doxygen{otb}{ImageFileReader} class.
//
//  Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
#include "otbImageFileReader.h"
// Software Guide : EndCodeSnippet

int main(int, char * argv[])
{
  // Software Guide : BeginLatex
  //
  // Then, the image type should be defined by specifying the
  // type used to represent pixels and the dimensions of the image.
  //
  // Software Guide : EndLatex

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

  typedef otb::Image<PixelType, Dimension> ImageType;
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // Using the image type, it is now possible to instantiate the image reader
  // class. The image type is used as a template parameter to define how the
  // data will be represented once it is loaded into memory. This type does
  // not have to correspond exactly to the type stored in the file. However,
  // a conversion based on C-style type casting is used, so the type chosen
  // to represent the data on disk must be sufficient to characterize it
  // accurately. Readers do not apply any transformation to the pixel data
  // other than casting from the pixel type of the file to the pixel type of
  // the ImageFileReader. The following illustrates a typical
  // instantiation of the ImageFileReader type.
  //
  // \index{otb::ImageFileReader!Instantiation}
  // \index{otb::Image!read}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  typedef otb::ImageFileReader<ImageType> ReaderType;
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // The reader type can now be used to create one reader object.  A
  // \doxygen{itk}{SmartPointer} (defined by the \code{::Pointer}
  // notation) is used to receive the reference to the newly created
  // reader.  The \code{New()}
  // method is invoked to create an instance of the image reader.
  //
  // \index{otb::ImageFileReader!New()}
  // \index{otb::ImageFileReader!Pointer}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  ReaderType::Pointer reader = ReaderType::New();
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // The minimum information required by the reader is the filename
  // of the image to be loaded in memory. This is provided through
  // the \code{SetFileName()} method. The file format here is inferred
  // from the filename extension. The user may also explicitly specify the
  // data format explicitly using the \doxygen{itk}{ImageIO} (See
  // Chapter~\ref{sec:ImagReadWrite} \pageref{sec:ImagReadWrite} for more
  // information):
  //
  // \index{otb::ImageFileReader!SetFileName()}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  const char * filename = argv[1];
  reader->SetFileName(filename);
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // Reader objects are referred to as pipeline source objects; they
  // respond to pipeline update requests and initiate the data flow in the
  // pipeline. The pipeline update mechanism ensures that the reader only
  // executes when a data request is made to the reader and the reader has
  // not read any data.  In the current example we explicitly invoke the
  // \code{Update()} method because the output of the reader is not connected
  // to other filters. In normal application the reader's output is connected
  // to the input of an image filter and the update invocation on the filter
  // triggers an update of the reader. The following line illustrates how an
  // explicit update is invoked on the reader.
  //
  // \index{otb::ImageFileReader!Update()}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  reader->Update();
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // Access to the newly read image can be gained by calling the
  // \code{GetOutput()} method on the reader. This method can also be called
  // before the update request is sent to the reader.  The reference to the
  // image will be valid even though the image will be empty until the reader
  // actually executes.
  //
  // \index{otb::ImageFileReader!GetOutput()}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  ImageType::Pointer image = reader->GetOutput();
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // Any attempt to access image data before the reader executes will yield
  // an image with no pixel data. It is likely that a program crash will
  // result since the image will not have been properly initialized.
  //
  // Software Guide : EndLatex

  return EXIT_SUCCESS;
}