/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: ShapedNeighborhoodIterators1.cxx,v $
  Language:  C++
  Date:      $Date: 2005/02/08 03:59:00 $
  Version:   $Revision: 1.19 $

  Copyright (c) Insight Software Consortium. All rights reserved.
  See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.

     This software is distributed WITHOUT ANY WARRANTY; without even 
     the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR 
     PURPOSE.  See the above copyright notices for more information.

=========================================================================*/
#if defined(_MSC_VER)
#pragma warning ( disable : 4786 )
#endif
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkNeighborhoodAlgorithm.h"
#include <math.h>

// Software Guide : BeginLatex
//
// This example uses \doxygen{ShapedNeighborhoodIterator} to implement a binary
// erosion algorithm.  If we think of an image $I$ as a set of pixel indices,
// then erosion of $I$ by a smaller set $E$, called the \emph{structuring
// element}, is the set of all indices at locations $x$ in $I$ such that when
// $E$ is positioned at $x$, every element in $E$ is also contained in $I$.
//
// This type of algorithm is easy to implement with shaped neighborhood
// iterators because we can use the iterator itself as the structuring element
// $E$ and move it sequentially through all positions $x$.  The result at $x$
// is obtained by checking values in a simple iteration loop through the
// neighborhood stencil.
//
// We need two iterators, a shaped iterator for the input image and a regular
// image iterator for writing results to the output image. 
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
#include "itkConstShapedNeighborhoodIterator.h"
#include "itkImageRegionIterator.h"
// Software Guide : EndCodeSnippet

int main( int argc, char ** argv )
{
  if ( argc < 4 )
    {
    std::cerr << "Missing parameters. " << std::endl;
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0]
              << " inputImageFile outputImageFile element_radius"
              << std::endl;
    return -1;
    }

  // Software Guide : BeginLatex
  //
  // Since we are working with binary images in this example, an \code{unsigned
  // char} pixel type will do.  The image and iterator types are defined using
  // the pixel type.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  typedef unsigned char PixelType;
  typedef itk::Image< PixelType, 2 >  ImageType;

  typedef itk::ConstShapedNeighborhoodIterator< 
                                          ImageType 
                                            > ShapedNeighborhoodIteratorType;

  typedef itk::ImageRegionIterator< ImageType> IteratorType;
  // Software Guide : EndCodeSnippet
  
  typedef itk::ImageFileReader< ImageType > ReaderType;    
  ReaderType::Pointer reader = ReaderType::New();
  reader->SetFileName( argv[1] );
  
  try
    {
    reader->Update();
    }
  catch ( itk::ExceptionObject &err)
    {
    std::cout << "ExceptionObject caught !" << std::endl; 
    std::cout << err << std::endl; 
    return -1;
    }

  ImageType::Pointer output = ImageType::New();
  output->SetRegions(reader->GetOutput()->GetRequestedRegion());
  output->Allocate();

// Software Guide : BeginLatex
//
// Refer to the examples in Section~\ref{sec:itkNeighborhoodIterator} or the
// source code of this example for a description of how to read the input image
// and allocate a matching output image.
//
// The size of the structuring element is read from the command line and used
// to define a radius for the shaped neighborhood iterator.  Using the method
// developed in section~\ref{sec:itkNeighborhoodIterator} to minimize bounds
// checking, the iterator itself is not initialized until entering the
// main processing loop.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  unsigned int element_radius = ::atoi( argv[3] );
  ShapedNeighborhoodIteratorType::RadiusType radius;
  radius.Fill(element_radius);
// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex
//
// The face calculator object introduced in
// Section~\ref{sec:NeighborhoodExample3} is created and used as before.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  typedef itk::NeighborhoodAlgorithm::ImageBoundaryFacesCalculator<
                                                ImageType > FaceCalculatorType;
  
  FaceCalculatorType faceCalculator;
  FaceCalculatorType::FaceListType faceList;
  FaceCalculatorType::FaceListType::iterator fit;
  
  faceList = faceCalculator( reader->GetOutput(), 
                             output->GetRequestedRegion(), 
                             radius );
// Software Guide : EndCodeSnippet 

// Software Guide : BeginLatex
//
// Now we initialize some variables and constants.
//
// Software Guide : EndLatex


// Software Guide : BeginCodeSnippet
  IteratorType out;
  
  const PixelType background_value = 0;
  const PixelType foreground_value = 255;
  const float rad = static_cast<float>(element_radius);
// Software Guide : EndCodeSnippet


// Software Guide : BeginLatex
//
// The outer loop of the algorithm is structured as in previous neighborhood
// iterator examples.  Each region in the face list is processed in turn.  As each new
// region is processed, the input and output iterators are initialized on that
// region.
//
// The shaped iterator that ranges over the input is our structuring element
// and its active stencil must be created accordingly.  For this example, the
// structuring element is shaped like a circle of radius
// \code{element\_radius}.  Each of the appropriate neighborhood offsets is
// activated in the double \code{for} loop.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
  for ( fit=faceList.begin(); fit != faceList.end(); ++fit)
    {
    ShapedNeighborhoodIteratorType it( radius, reader->GetOutput(), *fit );
    out = IteratorType( output, *fit );

    // Creates a circular structuring element by activating all the pixels less
    // than radius distance from the center of the neighborhood.
  
    for (float y = -rad; y <= rad; y++)
      {
      for (float x = -rad; x <= rad; x++)
        {     
        ShapedNeighborhoodIteratorType::OffsetType off;
        
        float dis = ::sqrt( x*x + y*y );
        if (dis <= rad)
          {
          off[0] = static_cast<int>(x);
          off[1] = static_cast<int>(y);
          it.ActivateOffset(off);
          }
        }
      }
// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex
//
// The inner loop, which implements the erosion algorithm, is fairly simple.
// The \code{for} loop steps the input and output iterators through their
// respective images.  At each step, the active stencil of the shaped iterator
// is traversed to determine whether all pixels underneath the stencil contain
// the foreground value, i.e. are contained within the set $I$.  Note the use
// of the stencil iterator, \code{ci}, in performing this check.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
    
    // Implements erosion
    for (it.GoToBegin(), out.GoToBegin(); !it.IsAtEnd(); ++it, ++out)
      {
      ShapedNeighborhoodIteratorType::ConstIterator ci;

      bool flag = true;
      for (ci = it.Begin(); ci != it.End(); ci++)
        {
        if (ci.Get() == background_value)
          {
          flag = false;
          break;
          }
        }
      if (flag == true)
        {
        out.Set(foreground_value);
        }
      else
        {
        out.Set(background_value);
        }
      }
    }
// Software Guide : EndCodeSnippet
  
  typedef itk::ImageFileWriter< ImageType > WriterType;
  
  WriterType::Pointer writer = WriterType::New();
  writer->SetFileName( argv[2] );
  writer->SetInput( output );
  try
    {
    writer->Update();
    }
  catch ( itk::ExceptionObject &err)
    {
    std::cout << "ExceptionObject caught !" << std::endl;
    std::cout << err << std::endl;
    return -1;
    }

  return 0;
}
