BoxFilter.h

Go to the documentation of this file.

/*
* 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/>.
*/

#ifndef __parallelsurf_boxfilter_h
#define __parallelsurf_boxfilter_h

#include "MathStuff.h"

namespace parallelsurf {

class Image;

class BoxFilter
{
public:
        BoxFilter(double iBaseSize, Image& iImage);

        void                            setY(unsigned int y);
        double getDxxWithX(unsigned int x) const;
        double getDyyWithX(unsigned int x) const;
        double getDxyWithX(unsigned int x) const;
        double getDetWithX(unsigned int x) const;

        bool checkBounds(int x, int y) const;

        // orig image info
        double**        _ii;
        unsigned int    _im_width;
        unsigned int    _im_height;

        int _basesize;

        // precomp values for det
        double _sqCorrectFactor;


        // the relative values of rectangle position for the first derivatives on x
        int _lxy_d2;

        // new ones
        int _lxx_x_mid;
        int _lxx_x_right;
        int _lxx_y_bottom;

        // stored Y

        unsigned int _y_minus_lxx_y_bottom;
        unsigned int _y_plus_lxx_y_bottom;
        unsigned int _y_minus_lxx_x_right;
        unsigned int _y_plus_lxx_x_right;
        unsigned int _y_minus_lxx_x_mid;
        unsigned int _y_plus_lxx_x_mid;
        unsigned int _y_minus_lxy_d2;
        unsigned int _y_plus_lxy_d2;
        unsigned int _y;

};

inline BoxFilter::BoxFilter(double iBaseSize, Image& iImage)
{
        _ii = iImage.getIntegralImage();
        _im_width = iImage.getWidth();
        _im_height = iImage.getHeight();

        _basesize = Math::Round(iBaseSize); // convert to integer


        // precomputed values for det
        double aCorrectFactor = 9.0 / (iBaseSize * iBaseSize);
        _sqCorrectFactor = aCorrectFactor * aCorrectFactor;

        // the values for lxy are all positive. will negate in the getDxy
        _lxy_d2 = ((int)(iBaseSize * 3) - 1) / 2 - 1;

        // new ones
        _lxx_x_mid = _basesize / 2;
        _lxx_x_right = _lxx_x_mid + _basesize;
        _lxx_y_bottom = _lxx_x_mid * 2;
}

#define CALC_INTEGRAL_SURFACE(II, STARTX, ENDX, STARTY, ENDY) \
        (II[ENDY+1][ENDX+1] + II[STARTY][STARTX] - II[ENDY+1][STARTX] - II[STARTY][ENDX+1])

inline double BoxFilter::getDxxWithX(unsigned int x) const
{
        return  CALC_INTEGRAL_SURFACE(_ii,x - _lxx_x_right,     x + _lxx_x_right, _y_minus_lxx_y_bottom, _y_plus_lxx_y_bottom)
                - 3.0 * CALC_INTEGRAL_SURFACE(_ii,x - _lxx_x_mid,       x + _lxx_x_mid,   _y_minus_lxx_y_bottom, _y_plus_lxx_y_bottom);
}

inline double BoxFilter::getDyyWithX(unsigned int x) const
{
        // calculates the Lyy convolution a point x,y with filter base size, using integral image
        // use the values of Lxx, but rotate them.
        return  CALC_INTEGRAL_SURFACE(_ii,              x - _lxx_y_bottom,              x + _lxx_y_bottom, _y_minus_lxx_x_right, _y_plus_lxx_x_right)
                -  3.0 * CALC_INTEGRAL_SURFACE(_ii,     x - _lxx_y_bottom,              x + _lxx_y_bottom, _y_minus_lxx_x_mid, _y_plus_lxx_x_mid);
}

inline double BoxFilter::getDxyWithX(unsigned int x) const
{
        // calculates the Lxy convolution a point x,y with filter base size, using integral image

        return  CALC_INTEGRAL_SURFACE(_ii,              x,                                              x + _lxy_d2, _y,                        _y_plus_lxy_d2)
                +       CALC_INTEGRAL_SURFACE(_ii,              x - _lxy_d2,                    x, _y_minus_lxy_d2,                     _y)
                -       CALC_INTEGRAL_SURFACE(_ii,              x,                                              x + _lxy_d2, _y_minus_lxy_d2,                   _y)
                -       CALC_INTEGRAL_SURFACE(_ii,              x - _lxy_d2,                    x, _y,                  _y_plus_lxy_d2);
}

#undef CALC_INTEGRAL_SURFACE

inline double BoxFilter::getDetWithX(unsigned int x) const
{
        double aDxy = getDxyWithX(x) * 0.9 * 2 / 3.0;
        double aDxx = getDxxWithX(x);
        double aDyy = getDyyWithX(x);

        return  ((aDxx * aDyy) - (aDxy * aDxy)) * _sqCorrectFactor;
}

inline void     BoxFilter::setY(unsigned int y)
{
        _y_minus_lxx_y_bottom = y - _lxx_y_bottom;
        _y_plus_lxx_y_bottom = y + _lxx_y_bottom;
        _y_minus_lxx_x_right = y - _lxx_x_right;
        _y_plus_lxx_x_right = y + _lxx_x_right;
        _y_minus_lxx_x_mid = y - _lxx_x_mid;
        _y_plus_lxx_x_mid = y + _lxx_x_mid;
        _y_minus_lxy_d2 = y - _lxy_d2;
        _y_plus_lxy_d2 = y + _lxy_d2;
        _y = y;

}

inline bool BoxFilter::checkBounds(int x, int y) const
{
        return (        x > _lxx_x_right && x + _lxx_x_right < (int)_im_width - 1
                        &&      y > _lxx_x_right && y + _lxx_x_right < (int)_im_height - 1);
}

} // namespace parallelsurf

#endif //__parallelsurf_boxfilter_h