[GRASS-user] circle surrounding neighbors

[bks at centrum.cz]

Sorry, I am a beginner... what shall I do with this gather-circle.c?
Thank you very much for your patience.
St.
______________________________________________________________
> Od: glynn at gclements.plus.com
> Komu: <bks at centrum.cz>
> CC: <grassuser at grass.itc.it>
> Datum: 30.07.2007 02:40
> Předmět: Re: [GRASS-user] circle surrounding neighbors
>
>bks at centrum.cz wrote:
>
>> don't you know about any possibility to use something similar to
r.neighbors
>> but  for the circle surrounding of the pixel?
>
>Modify raster/r.neighbors/gather.c.
>
>An (untested) attempt is attached.
>
>-- 
>Glynn Clements <glynn at gclements.plus.com>
>
>
>#include <grass/gis.h>
>#include "ncb.h"
>
>/*
>   given the starting col of the neighborhood,
>   copy the cell values from the bufs into the array of values
>   and return the number of values copied.
>*/
>
>static char **mask;
>
>static void init_mask(void)
>{
>    int i, j;
>
>    if (mask)
>	return;
>
>    mask = G_malloc(ncb.nsize * sizeof(char *));
>
>    for (i = 0; i < ncb.nsize; i++)
>	mask[i] = G_malloc(ncb.nsize);
>
>    for (i = 0; i < ncb.nsize; i++)
>	for (j = 0; j < ncb.nsize; j++)
>	    mask[i][j] = sqr(i - ncb.dist) + sqr(j - ncb.dist) <= sqr(ncb.dist);
>}
>
>int gather(DCELL *values, int offset)
>{
>    int row, col;
>    int n = 0;
>
>    *values = 0;
>
>    if (!mask)
>	init_mask();
>
>    for (row = 0; row < ncb.nsize; row++)
>	for (col = 0; col < ncb.nsize; col++)
>	{
>	    DCELL *c = &ncb.buf[row][offset + col];
>
>	    if (!mask[row][col])
>		continue;
>
>	    if (G_is_d_null_value(c))
>		G_set_d_null_value(&values[n], 1);
>	    else
>		values[n] = *c;
>
>	    n++;
>	}
>
>    return n ? n : -1;
>}
>
>
>