static int draw_boundaries(void)
{
if (Rast_raster_cmp(bl, br, map_type) != 0)
draw_bot();
if (Rast_raster_cmp(tr, br, map_type) != 0)
draw_rite();
return 0;
} /* draw_boundaries */
/************************************************************************
getpoint-- finds crossing point using linear interpolation,
converts from row-column to x-y space, and adds point to current line.
************************************************************************/
static void getpoint(struct cell *curr, double level,
struct Cell_head Cell, struct line_pnts *Points)
{
double x, y;
double ratio;
int p1, p2;
p1 = curr->edge;
p2 = (curr->edge + 1) % 4;
if (Rast_raster_cmp(&curr->z[p1], &curr->z[p2], DCELL_TYPE) == 0)
ratio = 1;
else if (Rast_is_d_null_value(&curr->z[p1]))
ratio = 1 / 2;
else if (Rast_is_d_null_value(&curr->z[p2]))
ratio = 1 / 2;
else
ratio = (level - curr->z[p1]) / (curr->z[p2] - curr->z[p1]);
switch (curr->edge) {
case 0:
y = curr->r;
x = curr->c + ratio;
break;
case 1:
y = curr->r + ratio;
x = curr->c + 1;
break;
case 2:
y = curr->r + 1;
x = curr->c + 1 - ratio;
break;
case 3:
y = curr->r + 1 - ratio;
x = curr->c;
break;
default:
G_fatal_error(_("Edge number out of range"));
}
/* convert r/c values to x/y values */
y = Cell.north - (y + .5) * Cell.ns_res;
x = Cell.west + (x + .5) * Cell.ew_res;
Vect_append_point(Points, x, y, level);
}