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/*
* Copyright (C) 2005-2022 Centre National d'Etudes Spatiales (CNES)
*
* This file is part of Orfeo Toolbox
*
* https://www.orfeo-toolbox.org/
*
* 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
*
* 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.
*/
/* Example usage:
./ImageRegionIteratorWithIndex Input/ROI_QB_MUL_2.tif Output/ImageRegionIteratorWithIndexOutput.jpg
*/
// \index{Iterators!speed}
// The ``WithIndex'' family of iterators was designed for algorithms that
// use both the value and the location of image pixels in calculations. Unlike
// \doxygen{itk}{ImageRegionIterator}, which calculates an index only when
// asked for, \doxygen{itk}{ImageRegionIteratorWithIndex} maintains its
// index location as a member variable that is updated during the increment or
// decrement process. Iteration speed is penalized, but the index queries are
// more efficient.
//
// \index{itk::ImageRegionIteratorWithIndex!example of using|(}
//
// The following example illustrates the use of
// ImageRegionIteratorWithIndex. The algorithm mirrors
// a 2D image across its $x$-axis (see \doxygen{itk}{FlipImageFilter} for an ND
// version). The algorithm makes extensive use of the \code{GetIndex()}
// method.
//
// We start by including the proper header file.
#include "otbImage.h"
#include "itkRGBPixel.h"
#include "itkImageRegionIteratorWithIndex.h"
#include "otbImageFileReader.h"
#include "otbImageFileWriter.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 outputImageFile" << std::endl;
return -1;
}
// For this example, we will use an RGB pixel type so that we can process color
// images. Like most other ITK image iterator,
// ImageRegionIteratorWithIndex class expects the image type as its
// single template parameter.
const unsigned int Dimension = 2;
using RGBPixelType = itk::RGBPixel<unsigned char>;
using ImageType = otb::Image<RGBPixelType, Dimension>;
using IteratorType = itk::ImageRegionIteratorWithIndex<ImageType>;
using ReaderType = otb::ImageFileReader<ImageType>;
using WriterType = otb::ImageFileWriter<ImageType>;
ImageType::ConstPointer inputImage;
ReaderType::Pointer reader = ReaderType::New();
reader->SetFileName(argv[1]);
try
{
reader->Update();
inputImage = reader->GetOutput();
}
catch (itk::ExceptionObject& err)
{
std::cout << "ExceptionObject caught !" << std::endl;
std::cout << err << std::endl;
return -1;
}
// An \code{ImageType} smart pointer called \code{inputImage} points to the
// output of the image reader. After updating the image reader, we can
// allocate an output image of the same size, spacing, and origin as the
// input image.
ImageType::Pointer outputImage = ImageType::New();
outputImage->SetRegions(inputImage->GetRequestedRegion());
outputImage->CopyInformation(inputImage);
outputImage->Allocate();
// Next we create the iterator that walks the output image. This algorithm
// requires no iterator for the input image.
IteratorType outputIt(outputImage, outputImage->GetRequestedRegion());
// This axis flipping algorithm works by iterating through the output image,
// querying the iterator for its index, and copying the value from the input
// at an index mirrored across the $x$-axis.
ImageType::IndexType requestedIndex = outputImage->GetRequestedRegion().GetIndex();
ImageType::SizeType requestedSize = outputImage->GetRequestedRegion().GetSize();
for (outputIt.GoToBegin(); !outputIt.IsAtEnd(); ++outputIt)
{
ImageType::IndexType idx = outputIt.GetIndex();
idx[0] = requestedIndex[0] + requestedSize[0] - 1 - idx[0];
outputIt.Set(inputImage->GetPixel(idx));
}
WriterType::Pointer writer = WriterType::New();
writer->SetFileName(argv[2]);
writer->SetInput(outputImage);
try
{
writer->Update();
}
catch (itk::ExceptionObject& err)
{
std::cout << "ExceptionObject caught !" << std::endl;
std::cout << err << std::endl;
return -1;
}
// Let's run this example on the image \code{ROI\_QB\_MUL\_2.tif} found in
// the \code{Examples/Data} directory.
// Figure~\ref{fig:ImageRegionIteratorWithIndexExample} shows how the original
// image has been mirrored across its $x$-axis in the output.
//
// \begin{figure} \center
// \includegraphics[width=0.44\textwidth]{ROI_QB_MUL_2.eps}
// \includegraphics[width=0.44\textwidth]{ImageRegionIteratorWithIndexOutput.eps}
// \itkcaption[Using the ImageRegionIteratorWithIndex]{Results of using
// ImageRegionIteratorWithIndex to mirror an image across an axis. The original
// image is shown at left. The mirrored output is shown at right.}
// \label{fig:ImageRegionIteratorWithIndexExample}
// \end{figure}
//
// \index{itk::ImageRegionIteratorWithIndex!example of using|)}
return EXIT_SUCCESS;
}
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