Examples/DataRepresentation/Image/Image1.cxx

/*=========================================================================
 *
 *  Copyright Insight Software Consortium
 *
 *  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.txt
 *
 *  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.
 *
 *=========================================================================*/

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

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

int main(int, char *[])
{
  // Software Guide : BeginLatex
  //
  // 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 \code{Image} class. Here we create
  // a 3D image with \code{unsigned short} pixel data.
  //
  // Software Guide : EndLatex
  //
  // Software Guide : BeginCodeSnippet
  typedef itk::Image< unsigned short, 3 > ImageType;
  // Software Guide : EndCodeSnippet


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


  // Software Guide : BeginLatex
  //
  // In ITK, 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 ITK 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 ITK, 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{Index} and
  // \doxygen{Size} classes. The origin of the region within the
  // image is defined by the \code{Index}. The extent, or size, of the region
  // is defined by the \code{Size}. 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 \code{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.
  //
  // \index{itk::Image!Size}
  // \index{itk::Image!SizeType}
  //
  // Software Guide : EndLatex
  //
  // Software Guide : BeginCodeSnippet
  ImageType::IndexType start;

  start[0] =   0;  // first index on X
  start[1] =   0;  // first index on Y
  start[2] =   0;  // first index on Z
  // Software Guide : EndCodeSnippet

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

  size[0]  = 200;  // size along X
  size[1]  = 200;  // size along Y
  size[2]  = 200;  // size along Z
  // Software Guide : EndCodeSnippet

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

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

  region.SetSize( size );
  region.SetIndex( start );
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // Finally, the region is passed to the \code{Image} object in order to define its
  // extent and origin. The \code{SetRegions} method sets the
  // \emph{LargestPossibleRegion}, \emph{BufferedRegion}, and \emph{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{itk::Image!Allocate()}
  // \index{itk::Image!SetRegions()}
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  image->SetRegions( region );
  image->Allocate();
  // Software Guide : EndCodeSnippet

  return EXIT_SUCCESS;
}