filter.h

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/*
Copyright (C) 2006 Pedro Felzenszwalb
 
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
*/
 
/* simple filters */
 
#ifndef FILTER_H
#define FILTER_H
 
#include <vector>
#include <cmath>
#include "image.h"
#include "misc.h"
#include "convolve.h"
#include "imconv.h"
 
#define WIDTH 4.0
 
namespace bp_single_thread_imp {
 
class FilterImage
{
public:
  /* normalize mask so it integrates to one */
  static void normalize(std::vector<float> &mask) {
    int len = mask.size();
    float sum = 0;
    for (int i = 1; i < len; i++) {
    sum += fabs(mask[i]);
    }
    sum = 2*sum + fabs(mask[0]);
    for (int i = 0; i < len; i++) {
    mask[i] /= sum;
    }
  }
 
  /* make filters */
  #define MAKE_FILTER(name, fun)                                \
  static std::vector<float> make_ ## name (float sigma) {       \
    sigma = std::max(sigma, 0.01F);            \
    int len = (int)ceil(sigma * WIDTH) + 1;                     \
    std::vector<float> mask(len);                               \
    for (int i = 0; i < len; i++) {                             \
    mask[i] = fun;                                            \
    }                                                           \
    return mask;                                                \
  }
 
  MAKE_FILTER(f0, exp(-0.5*square(i/sigma)));
 
  /* convolve image with gaussian filter */
  static image<float> *smooth(image<float> *src, float sigma) {
    std::vector<float> mask = make_f0(sigma);
    normalize(mask);
 
    image<float> *tmp = new image<float>(src->height(), src->width(), false);
    image<float> *dst = new image<float>(src->width(), src->height(), false);
    bp_single_thread_imp::Convolve::convolve_even(src, tmp, mask);
    bp_single_thread_imp::Convolve::convolve_even(tmp, dst, mask);
 
    delete tmp;
    return dst;
  }
 
  /* convolve image with gaussian filter */
  static image<float> *smooth(image<uchar> *src, float sigma) {
    image<float> *tmp = imageUCHARtoFLOAT(src);
    image<float> *dst = smooth(tmp, sigma);
    delete tmp;
    return dst;
  }
 
  /* compute laplacian */
  static image<float> *laplacian(image<float> *src) {
    int width = src->width();
    int height = src->height();
    image<float> *dst = new image<float>(width, height);
 
    for (int y = 1; y < height-1; y++) {
    for (int x = 1; x < width-1; x++) {
      float d2x = imRef(src, x-1, y) + imRef(src, x+1, y) -
    2*imRef(src, x, y);
      float d2y = imRef(src, x, y-1) + imRef(src, x, y+1) -
    2*imRef(src, x, y);
      imRef(dst, x, y) = d2x + d2y;
    }
    }
    return dst;
  }
};
 
};
 
#endif