/**
 * @file fastbilateral.cpp
 * @brief Fast bilateral filtering
 *
 *
 * This file is a part of LuminanceHDR package, based on pfstmo.
 * ----------------------------------------------------------------------
 * Copyright (C) 2003,2004 Grzegorz Krawczyk
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 * ----------------------------------------------------------------------
 *
 * @author Grzegorz Krawczyk, <krawczyk@mpi-sb.mpg.de>
 *
 * $Id: fastbilateral.cpp,v 1.5 2008/09/09 18:10:49 rafm Exp $
 */

#include <iostream>
#include <cmath>

#include <fftw3.h>

#include "Libpfs/array2d.h"
#include "Libpfs/progress.h"
#include "fastbilateral.h"

#ifdef BRANCH_PREDICTION
#define likely(x)       __builtin_expect((x),1)
#define unlikely(x)     __builtin_expect((x),0)
#else
#define likely(x)       (x)
#define unlikely(x)     (x)
#endif

using namespace std;

// TODO: use spatial convolution rather than FFT, should be much
// faster except for a very large kernels
class GaussianBlur
{
  float* source;
  fftwf_complex* freq;
  fftwf_plan fplan_fw;
  fftwf_plan fplan_in;

  float sigma;

public:
  GaussianBlur( int nx, int ny, float sigma ) : sigma( sigma )
  {
    int ox = nx;
    int oy = ny/2 + 1;            // saves half of the data
    const int osize = ox * oy;
    source =  (float*)fftwf_malloc(sizeof(float) * nx * 2 * (ny/2+1) );
    freq = (fftwf_complex*) fftwf_malloc(sizeof(fftwf_complex) * osize);
//    if( source == NULL || freq == NULL )
    //TODO: throw exception
    fplan_fw = fftwf_plan_dft_r2c_2d(nx, ny, source, freq, FFTW_ESTIMATE);
    fplan_in = fftwf_plan_dft_c2r_2d(nx, ny, freq, source, FFTW_ESTIMATE);
  }


  void blur( const pfs::Array2Df& I, pfs::Array2Df& J )
  {
    int x,y;

    int nx = I.getCols();
    int ny = I.getRows();
    int nsize = nx * ny;

    int ox = nx;
    int oy = ny/2 + 1;            // saves half of the data

    for( y=0 ; y<ny ; y++ )
      for( x=0 ; x<nx ; x++ )
        source[x*ny+y] = I(x,y);

    fftwf_execute(fplan_fw);

    // filter
    float sig = nx/(2.0f*sigma);
    float sig2 = 2.0f*sig*sig;
    for( x=0 ; x<ox/2 ; x++ )
      for( y=0 ; y<oy ; y++ )
      {
        float d2 = x*x + y*y;
        float kernel = exp( -d2 / sig2 );

        freq[x*oy+y][0] *= kernel;
        freq[x*oy+y][1] *= kernel;
        freq[(ox-x-1)*oy+y][0] *= kernel;
        freq[(ox-x-1)*oy+y][1] *= kernel;
      }

    fftwf_execute(fplan_in);

    for( x=0 ; x<nx ; x++ )
      for( y=0 ; y<ny ; y++ )
        J(x,y) = source[x*ny+y] / nsize;
  }

  ~GaussianBlur()
  {
    fftwf_free(source);
    fftwf_free(freq);
    fftwf_destroy_plan(fplan_fw);
    fftwf_destroy_plan(fplan_in);
  }


};


// According to the original paper, downsampling can be used to speed
// up computation. However, downsampling cannot be mathematically
// justified and introduces large errors (mostly excessive bluring) in
// the result of the bilateral filter. Therefore, in this
// implementation, downsampling is disabled.

#if 0
/**
 * @brief upsampling and downsampling
 *
 * original code from pfssize
 */
void upsampleArray( const pfs::Array2D *in, pfs::Array2D *out )
{
  float dx = (float)in->getCols() / (float)out->getCols();
  float dy = (float)in->getRows() / (float)out->getRows();

  float pad;

  float filterSamplingX = max( modff( dx, &pad ), 0.01f );
  float filterSamplingY = max( modff( dy, &pad ), 0.01f );

  const int outRows = out->getRows();
  const int outCols = out->getCols();

  const float inRows = in->getRows();
  const float inCols = in->getCols();

  const float filterSize = 1;

  float sx, sy;
  int x, y;
  for( y = 0, sy = -0.5 + dy/2; y < outRows; y++, sy += dy )
    for( x = 0, sx = -0.5 + dx/2; x < outCols; x++, sx += dx ) {

      float pixVal = 0;
      float weight = 0;

      for( float ix = max( 0, ceilf( sx-filterSize ) ); ix <= min( floorf(sx+filterSize), inCols-1 ); ix++ )
        for( float iy = max( 0, ceilf( sy-filterSize ) ); iy <= min( floorf( sy+filterSize), inRows-1 ); iy++ ) {
          float fx = fabs( sx - ix );
          float fy = fabs( sy - iy );

          const float fval = (1.0f-fx)*(1.0f-fy);

          pixVal += (*in)( (int)ix, (int)iy ) * fval;
          weight += fval;
        }

      if( weight == 0 ) {
        fprintf( stderr, "%g %g %g %g\n", sx, sy, dx, dy );
      }
//      assert( weight != 0 );
      (*out)(x,y) = pixVal / weight;

    }
}

void downsampleArray( const pfs::Array2D *in, pfs::Array2D *out )
{
  const float inRows = in->getRows();
  const float inCols = in->getCols();

  const int outRows = out->getRows();
  const int outCols = out->getCols();

  const float dx = (float)in->getCols() / (float)out->getCols();
  const float dy = (float)in->getRows() / (float)out->getRows();

  const float filterSize = 0.5;

  float sx, sy;
  int x, y;

  for( y = 0, sy = dy/2-0.5; y < outRows; y++, sy += dy )
    for( x = 0, sx = dx/2-0.5; x < outCols; x++, sx += dx ) {

      float pixVal = 0;
      float w = 0;
      for( float ix = max( 0, ceilf( sx-dx*filterSize ) ); ix <= min( floorf( sx+dx*filterSize ), inCols-1 ); ix++ )
        for( float iy = max( 0, ceilf( sy-dx*filterSize ) ); iy <= min( floorf( sy+dx*filterSize), inRows-1 ); iy++ ) {
          pixVal += (*in)( (int)ix, (int)iy );
          w += 1;
        }
      (*out)(x,y) = pixVal/w;
    }
}

#endif

/*
Pseudocode from the paper:

PiecewiseBilateral (Image I, spatial kernel fs , intensity influence gr )
  J=0 // set the output to zero
  for j=0..NB SEGMENTS
    ij= minI+j.*(max(I)-min(I))/NB SEGMENTS
    Gj=gr (I - ij ) // evaluate gr at each pixel
    Kj=Gj x fs // normalization factor
    Hj=Gj .* I // compute H for each pixel
    Hj=Hj x fs
    Jj=Hj ./ Kj // normalize
    J=J+Jj .*  InterpolationWeight(I, ij )
*/

void fastBilateralFilter(const pfs::Array2Df& I, pfs::Array2Df& J,
                         float sigma_s, float sigma_r, int /*downsample*/,
                         pfs::Progress &ph)
{
  int w = I.getCols();
  int h = I.getRows();
  int size = w * h;

  // find range of values in the input array
  float maxI = I(0);
  float minI = I(0);
  for (int i=0 ; i<size ; i++)
  {
    float v = I(i);
    if( unlikely( v>maxI ) ) maxI = v;
    if( unlikely( v<minI ) ) minI = v;
    J(i) = 0.0f;             // zero output
  }

  pfs::Array2Df* JJ;
//  if( downsample != 1 )
//    JJ = new pfs::Array2D(w,h);

//  w /= downsample;
//  h /= downsample;

  int sizeZ = w*h;
//  pfs::Array2D* Iz = new pfs::Array2D(w,h);
//  downsampleArray(I,Iz);
  const pfs::Array2Df* Iz = &I;
//  sigma_s /= downsample;

  pfs::Array2Df* jJ = new pfs::Array2Df(w,h);
  pfs::Array2Df* jG = new pfs::Array2Df(w,h);
  pfs::Array2Df* jK = new pfs::Array2Df(w,h);
  pfs::Array2Df* jH = new pfs::Array2Df(w,h);

  const int NB_SEGMENTS = (int)ceil((maxI-minI)/sigma_r);
  float stepI = (maxI-minI)/NB_SEGMENTS;

  GaussianBlur gaussian_blur( w, h, sigma_s );

  // piecewise bilateral
  for( int j=0 ; j<NB_SEGMENTS ; j++ )
  {
    ph.setValue( j * 100 / NB_SEGMENTS );
    if (ph.canceled())
        break;

    float jI = minI + j*stepI;        // current intensity value

    for (int i=0 ; i<sizeZ ; i++)
    {
      float dI = (*Iz)(i)-jI;
      (*jG)(i) = exp( -(dI*dI) / (sigma_r*sigma_r) );
      (*jH)(i) = (*jG)(i) * I(i);
    }

    gaussian_blur.blur( *jG, *jK );
    gaussian_blur.blur( *jH, *jH );

//    convolveArray(jG, sigma_s, jK);
//    convolveArray(jH, sigma_s, jH);

    for (int i=0 ; i<sizeZ ; i++ )
      if( likely((*jK)(i)!=0.0f) )
        (*jJ)(i) = (*jH)(i) / (*jK)(i);
      else
        (*jJ)(i) = 0.0f;

    //  if( downsample == 1 )
      JJ = jJ;                  // No upsampling is necessary
//    else
//      upsampleArray(jJ,JJ);

    if( j == 0 ) {
      // if the first segment - to account for the range boundary
      for (int i=0 ; i<size ; i++ )
      {
        if( likely( I(i) > jI + stepI ) )
          continue;             // wi = 0;
        if( likely( I(i) > jI ) ) {
          float wi = (stepI - (I(i)-jI)) / stepI;
          J(i) += (*JJ)(i)*wi;
        } else
          J(i) += (*JJ)(i);
      }
    } else if( j == NB_SEGMENTS-1 ) {
      // if the last segment - to account for the range boundary
      for (int i=0 ; i<size ; i++ )
      {
        if( likely( I(i) < jI - stepI ) )
          continue;             // wi = 0;
        if( likely( I(i) < jI ) ) {
          float wi = (stepI - (jI-I(i))) / stepI;
          J(i) += (*JJ)(i)*wi;
        } else
          J(i) += (*JJ)(i);
      }
    } else {
      for(int i=0 ; i<size ; i++ )
      {
        float wi = (stepI - fabs( I(i)-jI )) / stepI;
        if( unlikely( wi>0.0f ) )
          J(i) += (*JJ)(i)*wi;
      }
    }
  }

//  delete Iz;
//  if( downsample != 1 )
//    delete JJ;
  delete jJ;
  delete jG;
  delete jK;
  delete jH;
}
