Image.cpp

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/*
* This file is part of Parallel SURF, which implements the SURF algorithm
* using multi-threading.
*
* Copyright (C) 2010 David Gossow
*
* It is based on the SURF implementation included in Pan-o-matic 0.9.4, 
* written by Anael Orlinski.
* 
* Parallel SURF 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 3 of the License, or
* (at your option) any later version.
* 
* Parallel SURF 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, see <http://www.gnu.org/licenses/>.
*/

#include "Image.h"

using namespace parallelsurf;

Image::Image(const unsigned char **iPixels, unsigned int iWidth, unsigned int iHeight)
{
  init(iPixels, iWidth, iHeight);
}

void Image::init(const unsigned char **iPixels, unsigned int iWidth, unsigned int iHeight)
{
  // store values
  _width = iWidth;
  _height = iHeight;
  _pixels = iPixels;

  // allocate the integral image data
  _ii = AllocateImage(_width + 1, _height + 1);

  // create the integral image
  buildIntegralImage();
}

void Image::clean()
{
  if (_ii)
    DeallocateImage(_ii, _height + 1);
  _ii = 0;
}


Image::~Image()
{
  clean();
}

void Image::buildIntegralImage()
{
  // to make easier the later computation, shift the image by 1 pix (x and y)
  // so the image has a size of +1 for width and height compared to orig image.

  // fill first line with zero
  for(unsigned int i = 0; i <= _width; ++i)
    _ii[0][i] = 0;

  // fill first row with zero
  for(unsigned int i = 0; i <= _height; ++i)
    _ii[i][0] = 0;

  static const double norm=1.0 / 255.0;

  // compute all the others pixels
  for(unsigned int i = 1; i <= _height; ++i)
    for(unsigned int j = 1; j <= _width; ++j)
      _ii[i][j] = norm*double(_pixels[i-1][j-1]) + _ii[i-1][j] + _ii[i][j-1] - _ii[i-1][j-1];
/*
  //implementation suited for parallelized computation:
  // compute all the others pixels
  for(unsigned int i = 1; i <= _height; ++i)
    for(unsigned int j = 1; j <= _width; ++j)
      _ii[i][j] = norm*double(_pixels[i-1][j-1]) + _ii[i][j-1];
    
  for(unsigned int j = 1; j <= _width; ++j)
    for(unsigned int i = 1; i <= _height; ++i)
      _ii[i][j] += _ii[i-1][j];
    */
}

// allocate and deallocate pixels
double** Image::AllocateImage(unsigned int iWidth, unsigned int iHeight)
{
  // create the lines holder
  double ** aImagePtr = new double* [iHeight];

  // create the lines
  for(unsigned int i = 0; i < iHeight; ++i)
    aImagePtr[i] = new double[iWidth];

  // initialize image
  for(unsigned x = 0; x < iHeight; x++)
    for(unsigned y = 0; y < iWidth; y++)
        aImagePtr[x][y] = 0;

  return aImagePtr;
}

void Image::DeallocateImage(double **iImagePtr, unsigned int iHeight)
{
  // delete the lines
  for(unsigned int i = 0; i < iHeight; ++i)
    delete[] iImagePtr[i];

  // delete the lines holder
  delete[] iImagePtr;

}