text: /*
  Copyright (C) 2015 Yasutomo Kawanishi
  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
  */
  
  /* convolution */
  
  #ifndef CONVOLVE_H
  #define CONVOLVE_H
  
  #include <vector>
  #include <algorithm>
  #include <cmath>
  #include "image.h"
  
  /* convolve src with mask.  dst is flipped! */
  static void convolve_even(image<float> *src, image<float> *dst, 
  			  std::vector<float> &mask) {
    int width = src->width();
    int height = src->height();
    int len = mask.size();
  
    for (int y = 0; y < height; y++) {
      for (int x = 0; x < width; x++) {
        float sum = mask[0] * imRef(src, x, y);
        for (int i = 1; i < len; i++) {
  	sum += mask[i] * 
  	  (imRef(src, std::max(x-i,0), y) + 
  	   imRef(src, std::min(x+i, width-1), y));
        }
        imRef(dst, y, x) = sum;
      }
    }
  }
  
  /* convolve src with mask.  dst is flipped! */
  static void convolve_odd(image<float> *src, image<float> *dst, 
  			 std::vector<float> &mask) {
    int width = src->width();
    int height = src->height();
    int len = mask.size();
  
    for (int y = 0; y < height; y++) {
      for (int x = 0; x < width; x++) {
        float sum = mask[0] * imRef(src, x, y);
        for (int i = 1; i < len; i++) {
  	sum += mask[i] * 
  	  (imRef(src, std::max(x-i,0), y) - 
  	   imRef(src, std::min(x+i, width-1), y));
        }
        imRef(dst, y, x) = sum;
      }
    }
  }
  
  #endif
  