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/*=========================================================================
*
* 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.
*
*=========================================================================*/
#include "itkImage.h"
// Software Guide : BeginLatex
//
// The first thing required to read an image from a file is to include
// the header file of the \doxygen{ImageFileReader} class.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
#include "itkImageFileReader.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 = 3;
typedef itk::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{itk::ImageFileReader!Instantiation}
// \index{itk::Image!read}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
typedef itk::ImageFileReader< ImageType > ReaderType;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The reader type can now be used to create one reader object. A
// \doxygen{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{itk::ImageFileReader!New()}
// \index{itk::ImageFileReader!Pointer}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
ReaderType::Pointer reader = ReaderType::New();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The minimal 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 using the \doxygen{ImageIOBase} class (a list
// of possibilities can be found in the inheritance diagram of this
// class.).
//
// \index{itk::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{itk::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{itk::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;
}
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