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/****************************************************************************
*
* MODULE: r.buffer
*
* AUTHOR(S): Michael Shapiro - CERL
*
* PURPOSE: This program creates distance zones from non-zero
* cells in a grid layer. Distances are specified in
* meters (on the command-line). Window does not have to
* have square cells. Works both for planimetric
* (UTM, State Plane) and lat-long.
*
* COPYRIGHT: (C) 2005 by the GRASS Development Team
*
* This program is free software under the GNU General Public
* License (>=v2). Read the file COPYING that comes with GRASS
* for details.
*
****************************************************************************/
#include "distance.h"
int process_left(int from_row, int to_row, int start_col, int first_zone)
{
register int i, col, cur_zone;
register MAPTYPE *to_ptr, *from_ptr;
register int ncols, incr, farthest;
/* find cells to the left
* stop at left edge, or when ncols is bigger than the last zone,
* or when we see a 1 in the map
*/
col = start_col;
from_ptr = map + MAPINDEX(from_row, col);
to_ptr = map + MAPINDEX(to_row, col);
farthest = distances[ndist - 1].ncols;
/* planimetric grids will look for ncols^2
* and can use fact that (n+1)^2 = n^2 + 2n + 1
*/
if (window.proj != PROJECTION_LL)
incr = 1;
else
incr = 0;
ncols = 0;
while (1) {
if (col == 0) { /* global wrap-around */
if (!wrap_ncols)
break; /* only can happen with lat-lon */
col = window.cols;
ncols += wrap_ncols - 1;
from_ptr = map + MAPINDEX(from_row, col);
to_ptr = map + MAPINDEX(to_row, col);
}
col--;
if (incr) {
ncols += incr;
incr += 2;
}
else
ncols++;
if (ncols > farthest)
break;
if (*--from_ptr == 1)
break;
/* convert 1,2,3,4 to -1,0,1,2 etc. 0 becomes ndist */
if ((cur_zone = *--to_ptr))
cur_zone -= ZONE_INCR;
else
cur_zone = ndist;
/* find the first zone that is closer than the current value */
for (i = first_zone; i < cur_zone; i++) {
if (distances[i].ncols >= ncols) {
*to_ptr = (first_zone = i) + ZONE_INCR;
break;
}
}
}
return 0;
}
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