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 * __________________________________________________________________________ *
 *                 Multifunctional Library For Image Processing               *
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 *      (c) Copyright 2007 by Humbert Florent                                 *
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#include "SimplePeronaMalikFlow.hpp"
#include "operator/DifferentialOperators.hpp"
#include "MillieStd.hpp"

/*
 * Cet algorithme est fortement inspiré de l'algorithme de résolution proposé par Malik
 * et perona dans l'article :
 *    Scale-Space and Edge Detection Using Anisotropic Diffusion
 */

namespace Millie
{

  SimplePeronaMalikFlow::SimplePeronaMalikFlow(float lambda)
  {
    _lambda2 = Math::square(lambda);
  }



  float SimplePeronaMalikFlow::computeDiffusion(float v) const
  {
    return (_lambda2)/((_lambda2) + Math::square(v));
  }

 SimplePeronaMalikFlow* SimplePeronaMalikFlow::clone() const
 {
  return new SimplePeronaMalikFlow(*this);
 }

  float SimplePeronaMalikFlow::computeFlow(const Image & image, int x, int y, int canal) const
  {
    float current = image.getPixel(x,y, canal);
    int width = image.getWidth();
    int height = image.getHeight();


    int px = x-1;
    int nx = x+1;
    int py = y-1;
    int ny = y+1;
    if (px<0)
      px=0;
    if (nx>=width)
      nx=width-1;
    if (py<0)
      py=0;
    if (ny>=height)
      ny=height-1;

    float ixp = image.getPixel(px, y, canal);
    float ixn = image.getPixel(nx, y, canal);
    float iyp = image.getPixel(x, ny, canal);
    float iyn = image.getPixel(x, py, canal);

    float diffxn = computeDiffusion(current - ixn);
    float diffxp = computeDiffusion(current - ixp);
    float diffyn = computeDiffusion(current - iyn);
    float diffyp = computeDiffusion(current - ixp);


    float delta = (diffxn * (ixn - current))
                  + (diffxp * (ixp - current))
                  + (diffyp * (iyp - current))
                  + (diffyn * (iyn - current));


    return delta;
  }
}

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