ITK  5.0.0
Insight Segmentation and Registration Toolkit
Examples/IO/CovariantVectorImageRead.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 read an image whose pixel type is
// \code{CovariantVector}. For practical purposes this example is applicable
// to images of pixel type \doxygen{Vector}, \doxygen{Point} and
// \doxygen{FixedArray}. These pixel types are similar in that they are all
// arrays of fixed size in which the components have the same representation
// type.
//
// In this example we are reading a gradient image from a file (written in
// the previous example) and computing its magnitude using the
// \doxygen{VectorMagnitudeImageFilter}. Note that this filter is
// different from the \doxygen{GradientMagnitudeImageFilter} which actually
// takes a scalar image as input and computes the magnitude of its gradient.
// The VectorMagnitudeImageFilter class takes an image of vector
// pixel type as input and computes pixel-wise the magnitude of each vector.
//
// Let's start by including the relevant header files.
//
// \index{ImageFileRead!Vector images}
// \index{VectorMagnitudeImageFilter!header}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
#include "itkImage.h"
int main( int argc, char ** argv )
{
// Verify the number of parameters in the command line
if( argc < 3 )
{
std::cerr << "Usage: " << std::endl;
std::cerr << argv[0] << " inputImageFile outputVectorImageFile " << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// We read an image of \doxygen{CovariantVector} pixels and compute pixel
// magnitude to produce an image where each pixel is of type
// \code{unsigned short}. The components of the CovariantVector
// are selected to be \code{float} here. Notice that a renormalization is
// required in order to map the dynamic range of the magnitude values into
// the range of the output pixel type. The
// \doxygen{RescaleIntensityImageFilter} is used to achieve this.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using ComponentType = float;
constexpr unsigned int Dimension = 2;
using InputPixelType = itk::CovariantVector< ComponentType,
Dimension >;
using MagnitudePixelType = float;
using OutputPixelType = unsigned short;
using MagnitudeImageType = itk::Image< MagnitudePixelType, Dimension >;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The \doxygen{ImageFileReader} and \doxygen{ImageFileWriter}
// are instantiated using the image types.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The VectorMagnitudeImageFilter is instantiated using the
// input and output image types. A filter object is created with the
// \code{New()} method and assigned to a \doxygen{SmartPointer}.
//
// \index{VectorMagnitudeImageFilter!Instantiation}
// \index{VectorMagnitudeImageFilter!New()}
// \index{VectorMagnitudeImageFilter!Pointer}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using FilterType = itk::VectorMagnitudeImageFilter<
InputImageType,
MagnitudeImageType >;
FilterType::Pointer filter = FilterType::New();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The RescaleIntensityImageFilter class is instantiated next.
//
// \index{RescaleIntensityImageFilter!Instantiation}
// \index{RescaleIntensityImageFilter!New()}
// \index{RescaleIntensityImageFilter!Pointer}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using RescaleFilterType = itk::RescaleIntensityImageFilter<
MagnitudeImageType,
OutputImageType >;
RescaleFilterType::Pointer rescaler = RescaleFilterType::New();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// In the following the minimum and maximum values for the output image
// are specified. Note the use of the \doxygen{NumericTraits} class which
// allows us to define a number of type-related constants in a generic
// way. The use of traits is a fundamental characteristic of generic
// programming~\cite{Austern1999,Alexandrescu2001}.
//
// \index{RescaleIntensityImageFilter!SetOutputMinimum()}
// \index{RescaleIntensityImageFilter!SetOutputMaximum()}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
rescaler->SetOutputMinimum( itk::NumericTraits< OutputPixelType >::min() );
rescaler->SetOutputMaximum( itk::NumericTraits< OutputPixelType >::max() );
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Below, we create the reader and writer using the \code{New()} method and
// assign the result to a \doxygen{SmartPointer}.
//
// \index{itk::ImageFileReader!New()}
// \index{itk::ImageFileWriter!New()}
// \index{itk::ImageFileReader!SmartPointer}
// \index{itk::ImageFileWriter!SmartPointer}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
ReaderType::Pointer reader = ReaderType::New();
WriterType::Pointer writer = WriterType::New();
// Software Guide : EndCodeSnippet
// Here we recover the file names from the command line arguments
//
const char * inputFilename = argv[1];
const char * outputFilename = argv[2];
// Software Guide : BeginLatex
//
// The name of the file to be read or written is passed with the
// \code{SetFileName()} method.
//
// \index{itk::ImageFileReader!SetFileName()}
// \index{itk::ImageFileWriter!SetFileName()}
// \index{SetFileName()!itk::ImageFileReader}
// \index{SetFileName()!itk::ImageFileWriter}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
reader->SetFileName( inputFilename );
writer->SetFileName( outputFilename );
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Below we connect the reader, filter and writer to form the data
// processing pipeline.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->SetInput( reader->GetOutput() );
rescaler->SetInput( filter->GetOutput() );
writer->SetInput( rescaler->GetOutput() );
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Finally we execute the pipeline by invoking \code{Update()} on the
// writer. The call is placed in a \code{try/catch} block in case exceptions
// are thrown.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
try
{
writer->Update();
}
catch( itk::ExceptionObject & err )
{
std::cerr << "ExceptionObject caught !" << std::endl;
std::cerr << err << std::endl;
return EXIT_FAILURE;
}
// Software Guide : EndCodeSnippet
return EXIT_SUCCESS;
}