ITK  5.2.0
Insight Toolkit
Examples/Filtering/ThresholdImageFilter.cxx
/*=========================================================================
*
* Copyright NumFOCUS
*
* 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: {ThresholdImageFilterOutputBelow.png}
// OUTPUTS: {ThresholdImageFilterOutputAbove.png}
// OUTPUTS: {ThresholdImageFilterOutputOutside.png}
// Software Guide : EndCommandLineArgs
// Software Guide : BeginLatex
//
// \begin{figure}
// \center
// \includegraphics[height=5cm]{ThresholdTransferFunctionBelow}
// \includegraphics[height=5cm]{ThresholdImageFilterOutputBelow}
// \itkcaption[ThresholdImageFilter using the threshold-below
// mode.]{ThresholdImageFilter using the threshold-below mode.}
// \label{fig:ThresholdTransferFunctionBelow}
// \end{figure}
//
// \begin{figure}
// \center
// \includegraphics[height=5cm]{ThresholdTransferFunctionAbove}
// \includegraphics[height=5cm]{ThresholdImageFilterOutputAbove}
// \itkcaption[ThresholdImageFilter using the threshold-above
// mode]{ThresholdImageFilter using the threshold-above mode.}
// \label{fig:ThresholdTransferFunctionAbove}
// \end{figure}
//
// \begin{figure}
// \center
// \includegraphics[height=5cm]{ThresholdTransferFunctionOutside}
// \includegraphics[height=5cm]{ThresholdImageFilterOutputOutside}
// \itkcaption[ThresholdImageFilter using the threshold-outside
// mode]{ThresholdImageFilter using the threshold-outside mode.}
// \label{fig:ThresholdTransferFunctionOutside}
// \end{figure}
//
// This example illustrates the use of the \doxygen{ThresholdImageFilter}.
// This filter can be used to transform the intensity levels of an image in
// three different ways.
//
// \begin{itemize}
//
// \item First, the user can define a single threshold. Any pixels with
// values below this threshold will be replaced by a user defined value,
// called here the \code{OutsideValue}. Pixels with values above the
// threshold remain unchanged. This type of thresholding is illustrated in
// Figure~\ref{fig:ThresholdTransferFunctionBelow}.
//
// \item Second, the user can define a particular threshold such that all the
// pixels with values above the threshold will be replaced by the
// \code{OutsideValue}. Pixels with values below the threshold remain
// unchanged. This is illustrated in
// Figure~\ref{fig:ThresholdTransferFunctionAbove}.
//
// \item Third, the user can provide two thresholds. All the pixels with
// intensity values inside the range defined by the two thresholds will remain
// unchanged. Pixels with values outside this range will be assigned to the
// \code{OutsideValue}. This is illustrated in
// Figure~\ref{fig:ThresholdTransferFunctionOutside}.
//
// \end{itemize}
//
// The following methods choose among the three operating modes of the filter.
//
// \begin{itemize}
// \item \texttt{ThresholdBelow()}
// \item \texttt{ThresholdAbove()}
// \item \texttt{ThresholdOutside()}
// \end{itemize}
//
// \index{itk::ThresholdImageFilter!Instantiation}
// \index{itk::ThresholdImageFilter!Header}
// \index{itk::ThresholdImageFilter!ThresholdAbove()}
// \index{itk::ThresholdImageFilter!ThresholdBelow()}
// \index{itk::ThresholdImageFilter!ThresholdOutside()}
//
// The first step required to use this filter is to include its header file.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
#include "itkImage.h"
int
main(int argc, char * argv[])
{
if (argc < 5)
{
std::cerr << "Usage: " << argv[0] << " inputImageFile ";
std::cerr << " outputImageFile1 outputImageFile2 outputImageFile3"
<< std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// Then we must decide what pixel type to use for the image. This filter is
// templated over a single image type because the algorithm only modifies
// pixel values outside the specified range, passing the rest through
// unchanged.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using PixelType = unsigned char;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The image is defined using the pixel type and the dimension.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using ImageType = itk::Image<PixelType, 2>;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The filter can be instantiated using the image type defined above.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// An \doxygen{ImageFileReader} class is also instantiated in order to read
// image data from a file.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using ReaderType = itk::ImageFileReader<ImageType>;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// An \doxygen{ImageFileWriter} is instantiated in order to write the
// output image to a file.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
using WriterType = itk::ImageFileWriter<ImageType>;
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// Both the filter and the reader are created by invoking their
// \code{New()} methods and assigning the result to SmartPointers.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
ReaderType::Pointer reader = ReaderType::New();
FilterType::Pointer filter = FilterType::New();
// Software Guide : EndCodeSnippet
WriterType::Pointer writer = WriterType::New();
writer->SetInput(filter->GetOutput());
reader->SetFileName(argv[1]);
// Software Guide : BeginLatex
//
// The image obtained with the reader is passed as input to the
// \doxygen{ThresholdImageFilter}.
//
// \index{itk::ThresholdImageFilter!SetInput()}
// \index{itk::FileImageReader!GetOutput()}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->SetInput(reader->GetOutput());
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The method \code{SetOutsideValue()} defines the intensity value to be
// assigned to those pixels whose intensities are outside the range defined
// by the lower and upper thresholds.
//
// \index{itk::ThresholdImageFilter!SetOutsideValue()}
// \index{SetOutsideValue()!itk::ThresholdImageFilter}
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->SetOutsideValue(0);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The method \code{ThresholdBelow()} defines the intensity value below
// which pixels of the input image will be changed to the
// \code{OutsideValue}.
//
// \index{itk::ThresholdImageFilter!ThresholdBelow()}
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->ThresholdBelow(180);
// Software Guide : EndCodeSnippet
// Software Guide : BeginLatex
//
// The filter is executed by invoking the \code{Update()} method. If the
// filter is part of a larger image processing pipeline, calling
// \code{Update()} on a downstream filter will also trigger update of this
// filter.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->Update();
// Software Guide : EndCodeSnippet
writer->SetFileName(argv[2]);
writer->Update();
// Software Guide : BeginLatex
//
// The output of this example is shown in
// Figure~\ref{fig:ThresholdTransferFunctionBelow}. The second operating
// mode of the filter is now enabled by calling the method
// \code{ThresholdAbove()}.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->ThresholdAbove(180);
filter->Update();
// Software Guide : EndCodeSnippet
writer->SetFileName(argv[3]);
writer->Update();
// Software Guide : BeginLatex
//
// Updating the filter with this new setting produces the output shown in
// Figure~\ref{fig:ThresholdTransferFunctionAbove}. The third operating
// mode of the filter is enabled by calling \code{ThresholdOutside()}.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
filter->ThresholdOutside(170, 190);
filter->Update();
// Software Guide : EndCodeSnippet
writer->SetFileName(argv[4]);
writer->Update();
// Software Guide : BeginLatex
//
// The output of this third, ``band-pass'' thresholding mode is shown in
// Figure~\ref{fig:ThresholdTransferFunctionOutside}.
//
// The examples in this
// section also illustrate the limitations of the thresholding filter for
// performing segmentation by itself. These limitations are particularly
// noticeable in noisy images and in images lacking spatial uniformity, as
// is the case with MRI due to field bias.
//
// \relatedClasses
// \begin{itemize}
// \item \doxygen{BinaryThresholdImageFilter}
// \end{itemize}
//
// Software Guide : EndLatex
return EXIT_SUCCESS;
}
itkImageFileReader.h
itkImage.h
itkThresholdImageFilter.h
itk::ImageFileReader
Data source that reads image data from a single file.
Definition: itkImageFileReader.h:75
itk::ImageFileWriter
Writes image data to a single file.
Definition: itkImageFileWriter.h:87
itk::ThresholdImageFilter
Set image values to a user-specified value if they are below, above, or between simple threshold valu...
Definition: itkThresholdImageFilter.h:71
itkImageFileWriter.h
itk::Image
Templated n-dimensional image class.
Definition: itkImage.h:86