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/*=========================================================================
*
* 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
*
* https://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
//
// \doxygen{ImageRandomConstIteratorWithIndex} was developed to randomly
// sample pixel values. When incremented or decremented, it jumps to a random
// location in its image region.
//
// \index{itk::Image\-Random\-Const\-Iterator\-With\-Index!sample size}
// \index{itk::Image\-Random\-Const\-Iterator\-With\-Index!begin and end
// positions}
//
// The user must specify a sample size when creating this iterator. The sample
// size, rather than a specific image index, defines the end position for the
// iterator. \code{IsAtEnd()} returns
// \code{true} when the current sample number equals the sample size.
// \code{IsAtBegin()} returns \code{true} when the current sample number
// equals zero. An important difference from other image iterators is that
// ImageRandomConstIteratorWithIndex may visit the same pixel
// more than once.
//
// \index{itk::Image\-Random\-Const\-Iterator\-With\-Index!example of using|(}
// \index{itk::Image\-Random\-Const\-Iterator\-With\-Index!and statistics}
// Let's use the random iterator to estimate some simple image statistics. The
// next example calculates an estimate of the arithmetic mean of pixel values.
//
// First, include the appropriate header and declare pixel and image types.
//
// Software Guide : EndLatex
#include "itkImage.h"
// Software Guide : BeginCodeSnippet
#include "itkImageRandomConstIteratorWithIndex.h"
// Software Guide : EndCodeSnippet
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
int
main(int argc, char * argv[])
{
// Verify the number of parameters on the command line.
if (argc < 3)
{
std::cerr << "Missing parameters. " << std::endl;
std::cerr << "Usage: " << std::endl;
std::cerr << argv[0] << " inputImageFile numberOfSamples" << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginCodeSnippet
constexpr unsigned int Dimension = 2;
using PixelType = unsigned short;
using ImageType = itk::Image<PixelType, Dimension>;
using ConstIteratorType = itk::ImageRandomConstIteratorWithIndex<ImageType>;
// Software Guide : EndCodeSnippet
using ReaderType = itk::ImageFileReader<ImageType>;
ImageType::ConstPointer inputImage;
auto reader = ReaderType::New();
reader->SetFileName(argv[1]);
try
{
reader->Update();
inputImage = reader->GetOutput();
}
catch (const itk::ExceptionObject & err)
{
std::cerr << "ExceptionObject caught !" << std::endl;
std::cerr << err << std::endl;
return EXIT_FAILURE;
}
// Software Guide : BeginLatex
//
// The input image has been read as \code{inputImage}. We now create an
// iterator with a number of samples set by command line argument. The call
// to \code{ReinitializeSeed} seeds the random number generator. The
// iterator is initialized over the entire valid image region.
//
// \index{itk::Image\-Random\-Const\-Iterator\-With\-Index!SetNumberOfSamples()}
// \index{itk::Image\-Random\-Const\-Iterator\-With\-Index!ReinitializeSeed()}
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
ConstIteratorType inputIt(inputImage, inputImage->GetRequestedRegion());
inputIt.SetNumberOfSamples(std::stoi(argv[2]));
inputIt.ReinitializeSeed();
// Software Guide : EndCodeSnippet
// Software Guide: BeginLatex
//
// Now take the specified number of samples and calculate their average
// value.
//
// Software Guide : EndLatex
// Software Guide : BeginCodeSnippet
float mean = 0.0f;
for (inputIt.GoToBegin(); !inputIt.IsAtEnd(); ++inputIt)
{
mean += static_cast<float>(inputIt.Get());
}
mean = mean / std::stod(argv[2]);
// Software Guide : EndCodeSnippet
std::cout << "Mean estimate with " << argv[2] << " samples is " << mean
<< std::endl;
// Software Guide : BeginLatex
//
/*
The following table shows the results
of running this example on several of the data files from
\code{Examples/Data} with a range of sample sizes.
\begin{table}
\begin{center}
\begin{tabular}[]{rc|c|c|c}
& \multicolumn{4}{c}{\emph{Sample Size}} \\ & \code{\textbf{10}} &
\code{\textbf{100}} & \code{\textbf{1000}} & \code{\textbf{10000}} \\
\cline{2-5} \code{RatLungSlice1.mha} & 50.5 & 52.4 & 53.0 & 52.4 \\
\code{RatLungSlice2.mha} & 46.7 & 47.5 & 47.4 & 47.6 \\
\code{BrainT1Slice.png} & 47.2 & 64.1 & 68.0 & 67.8 \\ \end{tabular}
\itkcaption[ImageRandomConstIteratorWithIndex usage]{Estimates of mean
image pixel value using the ImageRandomConstIteratorWithIndex at
different sample sizes.} \end{center}
\label{tab:ImageRandomConstIteratorWithIndexExample}
\end{table}
\index{itk::Image\-Random\-Const\-Iterator\-With\-Index!example of
using|)}
*/
// Software Guide : EndLatex
return EXIT_SUCCESS;
}
|
