Image2.cxx

Example source code (Image2.cxx):

/*
 * Copyright (C) 1999-2011 Insight Software Consortium
 * Copyright (C) 2005-2020 Centre National d'Etudes Spatiales (CNES)
 *
 * This file is part of Orfeo Toolbox
 *
 *     https://www.orfeo-toolbox.org/
 *
 * 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
 *
 * 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.
 */


#include "otbImage.h"

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

#include "otbImageFileReader.h"

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

  using PixelType              = unsigned char;
  const unsigned int Dimension = 2;

  using ImageType = otb::Image<PixelType, Dimension>;

  // 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}

  using ReaderType = otb::ImageFileReader<ImageType>;

  // 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}

  ReaderType::Pointer reader = ReaderType::New();

  // 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()}

  const char* filename = argv[1];
  reader->SetFileName(filename);

  // 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()}

  reader->Update();

  // 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()}

  ImageType::Pointer image = reader->GetOutput();

  // 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.

  return EXIT_SUCCESS;
}