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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
//
// The \doxygen{ImageLinearIteratorWithIndex} is designed for line-by-line
// processing of an image.  It walks a linear path along a selected image
// direction parallel to one of the coordinate axes of the image. This
// iterator conceptually breaks an image into a set of parallel lines
// that span the selected image dimension.
//
// \index{Iterators!and image lines}
//
// Like all image iterators, movement of the
// ImageLinearIteratorWithIndex is constrained within an
// image region $R$.  The line $\ell$ through which the iterator moves is
// defined by selecting a direction and an origin.   The line $\ell$
// extends from the origin to the upper boundary of $R$. The origin can be
// moved to any position along the lower boundary of $R$.
//
// Several additional methods are defined for this iterator to control
// movement of the iterator along the line $\ell$ and movement of the origin
// of $\ell$.
//
// %Might need a figure here to describe this iterator.
//
// \begin{itemize}
//
// \index{itk::ImageLinearIteratorWithIndex!NextLine()}
//
// \item \textbf{\code{NextLine()}} Moves the iterator to the beginning pixel
// location of the next line in the image.  The origin of the next line is
// determined by incrementing the current origin along the fastest increasing
// dimension of the subspace of the image that excludes the selected
// dimension.
//
//
// \index{itk::ImageLinearIteratorWithIndex!PreviousLine()}
//
// \item \textbf{\code{PreviousLine()}} Moves the iterator to the \emph{last
// valid pixel location} in the previous line. The origin of the previous line
// is determined by decrementing the current origin along the fastest
// increasing dimension of the subspace of the image that excludes the
// selected dimension.
//
// \index{itk::ImageLinearIteratorWithIndex!GoToBeginOfLine()}
//
// \item \textbf{\code{GoToBeginOfLine()}} Moves the iterator to the beginning
// pixel of the current line.
//
// \index{itk::ImageLinearIteratorWithIndex!GoToEndOfLine()}
//
// \item \textbf{\code{GoToEndOfLine()}}  Moves the iterator to
// \emph{one past} the last valid pixel of the current line.
//
// \index{itk::ImageLinearIteratorWithIndex!GoToReverseBeginOfLine()}
//
// \item \textbf{\code{GoToReverseBeginOfLine()}}  Moves the iterator
// to \emph{the last valid pixel} of the current line.
//
// \index{itk::ImageLinearIteratorWithIndex!IsAtReverseEndOfLine()}
//
// \item \textbf{\code{IsAtReverseEndOfLine()}}
// Returns true if the iterator points
// to \emph{one position before} the beginning pixel of the current line.
//
// \index{itk::ImageLinearIteratorWithIndex!IsAtEndOfLine()}
//
// \item \textbf{\code{IsAtEndOfLine()}}
// Returns true if the iterator points to
// \emph{one position past} the last valid pixel of the current line.
// \end{itemize}
//
// The following code example shows how to use the
// ImageLinearIteratorWithIndex.  It implements the same algorithm as
// in the previous example, flipping an image across its $x$-axis.  Two line
// iterators are iterated in opposite directions across the $x$-axis.
// After each line is traversed, the iterator origins are stepped along
// the $y$-axis to the
// next line.
//
// \index{itk::ImageLinearIteratorWithIndex!example of using|(}
//
// Headers for both the const and non-const versions are needed.
//
// Software Guide : EndLatex

#include "itkImage.h"
#include "itkRGBPixel.h"
// Software Guide : BeginCodeSnippet
#include "itkImageLinearIteratorWithIndex.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 outputImageFile" << std::endl;
    return EXIT_FAILURE;
  }

  // Software Guide : BeginLatex
  //
  // The RGB image and pixel types are defined as in the previous example. The
  // ImageLinearIteratorWithIndex class and its const version each have
  // single template parameters, the image type.
  //
  // Software Guide : EndLatex

  constexpr unsigned int Dimension = 2;

  using RGBPixelType = itk::RGBPixel<unsigned char>;
  using ImageType = itk::Image<RGBPixelType, Dimension>;

  // Software Guide : BeginCodeSnippet
  using IteratorType = itk::ImageLinearIteratorWithIndex<ImageType>;
  using ConstIteratorType = itk::ImageLinearConstIteratorWithIndex<ImageType>;
  // Software Guide : EndCodeSnippet

  using ReaderType = itk::ImageFileReader<ImageType>;
  using WriterType = itk::ImageFileWriter<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 a !" << std::endl;
    std::cerr << err << std::endl;
    return EXIT_FAILURE;
  }

  // Software Guide : BeginLatex
  //
  // After reading the input image, we allocate an output image that of the
  // same size, spacing, and origin.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  auto outputImage = ImageType::New();
  outputImage->SetRegions(inputImage->GetRequestedRegion());
  outputImage->CopyInformation(inputImage);
  outputImage->Allocate();
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // Next we create the two iterators.  The const iterator walks the input
  // image, and the non-const iterator walks the output image.  The iterators
  // are initialized over the same region.  The direction of iteration is set
  // to 0, the $x$ dimension.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  ConstIteratorType inputIt(inputImage, inputImage->GetRequestedRegion());
  IteratorType      outputIt(outputImage, inputImage->GetRequestedRegion());

  inputIt.SetDirection(0);
  outputIt.SetDirection(0);
  // Software Guide : EndCodeSnippet

  // Software Guide: BeginLatex
  //
  // Each line in the input is copied to the output.  The input iterator moves
  // forward across columns while the output iterator moves backwards.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  for (inputIt.GoToBegin(), outputIt.GoToBegin(); !inputIt.IsAtEnd();
       outputIt.NextLine(), inputIt.NextLine())
  {
    inputIt.GoToBeginOfLine();
    outputIt.GoToEndOfLine();
    while (!inputIt.IsAtEndOfLine())
    {
      --outputIt;
      outputIt.Set(inputIt.Get());
      ++inputIt;
    }
  }
  // Software Guide : EndCodeSnippet

  auto writer = WriterType::New();
  writer->SetFileName(argv[2]);
  writer->SetInput(outputImage);
  try
  {
    writer->Update();
  }
  catch (const itk::ExceptionObject & err)
  {
    std::cerr << "ExceptionObject caught !" << std::endl;
    std::cerr << err << std::endl;
    return EXIT_FAILURE;
  }

  // Software Guide : BeginLatex
  //
  // Running this example on \code{VisibleWomanEyeSlice.png} produces
  // the same output image shown in
  // Figure~\ref{fig:ImageRegionIteratorWithIndexExample}.
  //
  // \index{itk::ImageLinearIteratorWithIndex!example of using|)}
  // Software Guide : EndLatex

  return EXIT_SUCCESS;
}
