Image1.cxx

Example source code (Image1.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.
 */


// This example illustrates how to manually construct an \doxygen{otb}{Image}
// class.  The following is the minimal code needed to instantiate, declare
// and create the image class.
//
// \index{Image!Instantiation}
// \index{Image!Header}
//
// First, the header file of the Image class must be included.

#include "otbImage.h"

int main(int, char* [])
{
  // Then we must decide with what type to represent the pixels
  // and what the dimension of the image will be. With these two
  // parameters we can instantiate the image class. Here we create
  // a 2D image, which is what we often use in remote sensing
  // applications, anyway, with \code{unsigned short} pixel data.
  //
  using ImageType = otb::Image<unsigned short, 2>;

  // The image can then be created by invoking the \code{New()} operator
  // from the corresponding image type and assigning the result
  // to a \doxygen{itk}{SmartPointer}.
  //
  // \index{Image!Pointer}
  // \index{Image!New()}
  //
  ImageType::Pointer image = ImageType::New();

  // In OTB, images exist in combination with one or more
  // \emph{regions}. A region is a subset of the image and indicates a
  // portion of the image that may be processed by other classes in
  // the system. One of the most common regions is the
  // \emph{LargestPossibleRegion}, which defines the image in its
  // entirety. Other important regions found in OTB are the
  // \emph{BufferedRegion}, which is the portion of the image actually
  // maintained in memory, and the \emph{RequestedRegion}, which is
  // the region requested by a filter or other class when operating on
  // the image.
  //
  // In OTB, manually creating an image requires that the image is
  // instantiated as previously shown, and that regions describing the image are
  // then associated with it.
  //
  // A region is defined by two classes: the \doxygen{itk}{Index} and
  // \doxygen{itk}{Size} classes. The origin of the region within the
  // image with which it is associated is defined by Index. The
  // extent, or size, of the region is defined by Size. Index
  // is represented by a n-dimensional array where each component is an
  // integer indicating---in topological image coordinates---the initial
  // pixel of the image. When an image is created manually, the user is
  // responsible for defining the image size and the index at which the image
  // grid starts. These two parameters make it possible to process selected
  // regions.
  //
  // The starting point of the image is defined by an Index class
  // that is an n-dimensional array where each component is an integer
  // indicating the grid coordinates of the initial pixel of the image.
  //
  // \index{Image!Size}
  // \index{Image!SizeType}
  //
  ImageType::IndexType start;

  start[0] = 0; // first index on X
  start[1] = 0; // first index on Y

  // The region size is represented by an array of the same dimension of the
  // image (using the Size class). The components of the array are
  // unsigned integers indicating the extent in pixels of the image along
  // every dimension.
  //
  // \index{Image!Index}
  // \index{Image!IndexType}
  //
  ImageType::SizeType size;

  size[0] = 200; // size along X
  size[1] = 200; // size along Y

  // Having defined the starting index and the image size, these two
  // parameters are used to create an ImageRegion object which basically
  // encapsulates both concepts. The region is initialized with the
  // starting index and size of the image.
  //
  // \index{Image!itk::ImageRegion}
  // \index{Image!RegionType}

  ImageType::RegionType region;

  region.SetSize(size);
  region.SetIndex(start);

  // Finally, the region is passed to the \code{Image} object in
  // order to define its extent and origin. The \code{SetRegions}
  // method sets the LargestPossibleRegion, BufferedRegion, and
  // RequestedRegion simultaneously. Note that none of the operations
  // performed to this point have allocated memory for the image pixel
  // data. It is necessary to invoke the \code{Allocate()} method to
  // do this. Allocate does not require any arguments since all the
  // information needed for memory allocation has already been
  // provided by the region.
  //
  // \index{Image!Allocate()}
  // \index{Image!SetRegions()}

  image->SetRegions(region);
  image->Allocate();

  return EXIT_SUCCESS;
}