ITK  4.6.0
Insight Segmentation and Registration Toolkit
Filtering/CurvatureFlowImageFilter.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 : BeginCommandLineArgs
// INPUTS: {BrainProtonDensitySlice.png}
// OUTPUTS: {CurvatureFlowImageFilterOutput.png}
// ARGUMENTS: 10 0.25
// Software Guide : EndCommandLineArgs
// Software Guide : BeginLatex
//
// The \doxygen{CurvatureFlowImageFilter} performs edge-preserving smoothing
// in a similar fashion to the classical anisotropic diffusion. The filter
// uses a level set formulation where the iso-intensity contours in a image
// are viewed as level sets, where pixels of a particular intensity form one
// level set. The level set function is then evolved under the control of
// a diffusion equation where the speed is proportional to the
// curvature of the contour:
//
// \begin{equation}
// I_t = \kappa |\nabla I|
// \end{equation}
//
// where $ \kappa $ is the curvature.
//
// Areas of high curvature will diffuse faster than areas of low curvature.
// Hence, small jagged noise artifacts will disappear quickly, while large
// scale interfaces will be slow to evolve, thereby preserving sharp
// boundaries between objects. However, it should be noted that although the
// evolution at the boundary is slow, some diffusion still occur. Thus,
// continual application of this curvature flow scheme will eventually
// result is the removal of information as each contour shrinks to a point
// and disappears.
//
// \index{itk::CurvatureFlowImageFilter}
//
// Software Guide : EndLatex
#include "itkImage.h"
// Software Guide : BeginLatex
//
// The first step required to use this filter is to include its header file.
//
// \index{itk::CurvatureFlowImageFilter!header}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
int main( int argc, char * argv[] )
{
if( argc < 5 )
{
std::cerr << "Usage: " << std::endl;
std::cerr << argv[0] << " inputImageFile outputImageFile numberOfIterations timeStep" << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// Types should be selected based on the pixel types required for the
// input and output images.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
typedef float InputPixelType;
typedef float OutputPixelType;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// With them, the input and output image types can be instantiated.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
typedef itk::Image< InputPixelType, 2 > InputImageType;
typedef itk::Image< OutputPixelType, 2 > OutputImageType;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The CurvatureFlow filter type is now instantiated using both the
// input image and the output image types.
//
// \index{itk::CurvatureFlowImageFilter!instantiation}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
InputImageType, OutputImageType > FilterType;
// Software Guide : EndCodeSnippet
ReaderType::Pointer reader = ReaderType::New();
reader->SetFileName( argv[1] );
// Software Guide : BeginLatex
//
// A filter object is created by invoking the \code{New()} method and
// assigning the result to a \doxygen{SmartPointer}.
//
// \index{itk::CurvatureFlowImageFilter!New()}
// \index{itk::CurvatureFlowImageFilter!Pointer}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
FilterType::Pointer filter = FilterType::New();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The input image can be obtained from the output of another filter. Here,
// an image reader is used as source.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->SetInput( reader->GetOutput() );
// Software Guide : EndCodeSnippet
const unsigned int numberOfIterations = atoi( argv[3] );
const double timeStep = atof( argv[4] );
// Software Guide : BeginLatex
//
// The CurvatureFlow filter requires two parameters, the number of
// iterations to be performed and the time step used in the computation of
// the level set evolution. These two parameters are set using the methods
// \code{SetNumberOfIterations()} and \code{SetTimeStep()} respectively.
// Then the filter can be executed by invoking \code{Update()}.
//
// \index{itk::CurvatureFlowImageFilter!Update()}
// \index{itk::CurvatureFlowImageFilter!SetTimeStep()}
// \index{itk::CurvatureFlowImageFilter!SetNumberOfIterations()}
// \index{SetTimeStep()!itk::CurvatureFlowImageFilter}
// \index{SetNumberOfIterations()!itk::CurvatureFlowImageFilter}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->SetNumberOfIterations( numberOfIterations );
filter->SetTimeStep( timeStep );
filter->Update();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Typical values for the time step are $0.125$ in $2D$ images and
// $0.0625$ in $3D$ images. The number of iterations can be usually around
// $10$, more iterations will result in further smoothing and will
// increase linearly the computing time. Edge-preserving behavior is not
// guaranteed by this filter, some degradation will occur on the edges and
// will increase as the number of iterations is increased.
//
// Software Guide : EndLatex
// Software Guide : BeginLatex
//
// If the output of this filter has been connected to other filters down
// the pipeline, updating any of the downstream filters will
// triggered the execution of this one. For example, a writer filter could
// have been used after the curvature flow filter.
//
// Software Guide : EndLatex
typedef unsigned char WritePixelType;
typedef itk::Image< WritePixelType, 2 > WriteImageType;
OutputImageType, WriteImageType > RescaleFilterType;
RescaleFilterType::Pointer rescaler = RescaleFilterType::New();
rescaler->SetOutputMinimum( 0 );
rescaler->SetOutputMaximum( 255 );
WriterType::Pointer writer = WriterType::New();
writer->SetFileName( argv[2] );
// Software Guide : BeginCodeSnippet
rescaler->SetInput( filter->GetOutput() );
writer->SetInput( rescaler->GetOutput() );
writer->Update();
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// \begin{figure}
// \center
// \includegraphics[width=0.44\textwidth]{BrainProtonDensitySlice}
// \includegraphics[width=0.44\textwidth]{CurvatureFlowImageFilterOutput}
// \itkcaption[CurvatureFlowImageFilter output]{Effect of the
// CurvatureFlowImageFilter on a slice from a MRI proton density image of
// the brain.}
// \label{fig:CurvatureFlowImageFilterInputOutput}
// \end{figure}
//
// Figure \ref{fig:CurvatureFlowImageFilterInputOutput} illustrates the
// effect of this filter on a MRI proton density image of the brain. In this
// example the filter was run with a time step of $0.25$ and $10$
// iterations. The figure shows how homogeneous regions are smoothed and
// edges are preserved.
//
// \relatedClasses
// \begin{itemize}
// \item \doxygen{GradientAnisotropicDiffusionImageFilter}
// \item \doxygen{CurvatureAnisotropicDiffusionImageFilter}
// \item \doxygen{BilateralImageFilter}
// \end{itemize}
//
// Software Guide : EndLatex
return EXIT_SUCCESS;
}