/*
Inside/Outside polygon filter
Copyright (C) 2002 Robert Lipe, robertlipe+source@gpsbabel.org
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 USA
*/
#include // for sscanf
#include // for strchr, strlen, strspn
#include // for foreach
#include "defs.h"
#include "filterdefs.h" // for global_waypoint_list
#include "polygon.h"
#include "gbfile.h" // for gbfclose, gbfgetstr, gbfopen, gbfile
#if FILTERS_ENABLED
#define MYNAME "Polygon filter"
/*
* This test for insideness is essentially an odd/even test. The
* traditional (simple) implementation of the odd/even test counts
* intersections along a test ray, and if it should happen to exactly hit
* a vertex of the polygon, it throws away the result and fires a different
* test ray. Since we're potentially testing hundreds of test points against
* a polygon with hundreds of sides, this seemed both wasteful and difficult
* to coordinate, so instead I added extra state to try to figure out what we
* would have seen if we had just missed the vertex. The result is the
* hodgepodge of "limbo" states explained below. On the credit side of the
* ledger, though, the tests for intersection are vastly simplified by always
* having a horizontal test ray.
*
* The general structure of this filter is: we loop over the points in the
* polygon. For each point, we update the state of each of the waypoints in
* the test set. Thus, the state of every waypoint is indeterminate until
* the end of the outer loop, at which point the state of every waypoint
* should theoretically be completely determined.
*
* The bits following this comment encode the current state of the test point
* as we go around the polygon. OUTSIDE clearly isn't a bit; it's just here
* for completeness. If it's not INSIDE, and it's not something else, it's
* clearly OUTSIDE.
*
* INSIDE is self-explanatory. What it means is that the last time we were
* certain of our state, we were inside of the polygon.
*
* LIMBO encodes a bit more state information, to handle the case where our
* test ray (a horizontal line) has intersected one of the vertices of the
* polygon exactly. If the two lines that meet at that vertex are on
* opposite sides of the test ray, it was an intersection. Otherwise, it just
* grazed a local minimum or maximum and so counted as either zero or two
* intersections - not a change in state. Horizontal lines encountered
* while in limbo don't change the limbo state. All other lines do.
* The rest of the bits talk about how we got into limbo, and thus what to do
* when we get out of limbo.
*
* LIMBO_UP means that the last line segment we saw going into limbo was
* headed upward. When we see another non-horizontal line segment, whether
* we flip the INSIDE bit or not depends on whether it also goes upward. If
* it does, we flip the INSIDE bit. Otherwise, we just clear our limbo state
* and go on as if nothing had happened.
*
* LIMBO_BEGIN means that the very first vertex in the polygon put us into a
* limbo state. We won't be able to resolve that limbo state until we get to
* the end of the cycle, and it can actually coexist with another more local
* limbo state. The next two bits talk about the beginning limbo state in
* more detail.
*
* BEGIN_UP means that the first non-horizontal line segment we encountered
* while in a LIMBO_BEGIN state went upward. As with LIMBO_UP, this is used
* to determine the final disposition of the limbo state when we get back
* around to the other end of the cycle.
*
* BEGIN_HOR is fairly temporary. It says that we've encountered one or more
* horizontal line segments at the beginning of the cycle, so we haven't yet
* been able to resolve the state of BEGIN_UP. It's a way of propagating the
* "firstness" forward until we can make a decision, without propagating it
* for every test point.
*
* UP is used to remember which way we were going in case we encounter a
* limbo state.
*
* -- RLP
*/
#define OUTSIDE 0
#define INSIDE 1
#define LIMBO 2
#define LIMBO_UP 4
#define LIMBO_BEGIN 8
#define BEGIN_UP 16
#define BEGIN_HOR 32
#define UP 64
void PolygonFilter::polytest(double lat1, double lon1,
double lat2, double lon2,
double wlat, double wlon,
unsigned short* state, int first, int last)
{
if (lat1 == wlat) {
if (lat2 < wlat) {
/* going down */
if (*state & LIMBO) {
if (*state & LIMBO_UP) {
*state = *state ^ INSIDE;
}
*state = *state & ~LIMBO &~LIMBO_UP;
} else if (*state & LIMBO_BEGIN) {
if (*state & BEGIN_HOR) {
*state = *state & ~BEGIN_HOR;
} else if (last) {
if (*state & BEGIN_UP) {
*state = *state ^ INSIDE;
}
*state = *state & ~LIMBO_BEGIN & ~BEGIN_UP;
}
} else if (first && (lon1 > wlon)) {
*state |= LIMBO_BEGIN;
}
} else if (lat2 == wlat) {
if (first & (lon1 > wlon || lon2 > wlon)) {
*state |= LIMBO_BEGIN | BEGIN_HOR;
} else if (last && (*state & LIMBO_BEGIN) && (*state & LIMBO)) {
if ((!!(*state & LIMBO_UP)) != (!!(*state & BEGIN_UP))) {
*state = *state ^ INSIDE;
}
*state = *state & ~LIMBO & ~LIMBO_UP &
~LIMBO_BEGIN & ~BEGIN_UP;
} else if (*state & LIMBO) {
/* do nothing */
} else {
if (lon1 <= wlon && lon2 > wlon) {
if (*state & UP) {
*state &= ~UP;
*state |= LIMBO_UP;
}
*state = *state | LIMBO;
}
}
} else {
/* going up */
if (*state & LIMBO) {
if (!(*state & LIMBO_UP)) {
*state = *state ^ INSIDE;
}
*state = *state & ~LIMBO & ~LIMBO_UP;
} else if (*state & LIMBO_BEGIN) {
if (*state & BEGIN_HOR) {
*state &= ~BEGIN_HOR;
*state |= BEGIN_UP;
} else if (last) {
if (!(*state & BEGIN_UP)) {
*state = *state ^ INSIDE;
}
*state = *state & ~LIMBO_BEGIN & ~BEGIN_UP;
}
} else if (first && (lon1 > wlon)) {
*state |= LIMBO_BEGIN | BEGIN_UP;
}
}
*state = *state & ~UP;
} else if (lat2 == wlat) {
if (lat1 < wlat) {
if (last) {
if (*state & BEGIN_UP) {
*state = *state ^ INSIDE;
}
*state = *state & ~LIMBO_BEGIN & ~BEGIN_UP;
} else if (lon2 > wlon) {
*state |= LIMBO;
}
}
/* no case for lat1==wlat; that's above */
else {
if (last) {
if (!(*state & BEGIN_UP)) {
*state = *state ^ INSIDE;
}
*state = *state & ~LIMBO_BEGIN & ~BEGIN_UP;
} else if (lon2 > wlon) {
*state |= LIMBO | LIMBO_UP;
} else {
*state |= UP;
}
}
} else {
if ((lat1 > wlat && lat2 < wlat) ||
(lat1 < wlat && lat2 > wlat)) {
/* we only care if the lines might intersect */
if (lon1 > wlon && lon2 > wlon) {
*state = *state ^ INSIDE;
} else if (!(lon1 <= wlon && lon2 <= wlon)) {
/* we're inside the bbox of a diagonal line. math time. */
double loni = lon1+(lon2-lon1)/(lat2-lat1)*(wlat-lat1);
if (loni > wlon) {
*state = *state ^ INSIDE;
}
}
}
}
}
#define BADVAL 999999
void PolygonFilter::process()
{
extra_data* ed;
int fileline = 0;
int first = 1;
int last = 0;
char* line;
gbfile* file_in = gbfopen(polyfileopt, "r", MYNAME);
double olat = BADVAL;
double olon = BADVAL;
double lat1 = BADVAL;
double lon1 = BADVAL;
double lat2 = BADVAL;
double lon2 = BADVAL;
while ((line = gbfgetstr(file_in))) {
fileline++;
char* pound = strchr(line, '#');
if (pound) {
*pound = '\0';
}
lat2 = lon2 = BADVAL;
int argsfound = sscanf(line, "%lf %lf", &lat2, &lon2);
if (argsfound != 2 && strspn(line, " \t\n") < strlen(line)) {
warning(MYNAME
": Warning: Polygon file contains unusable vertex on line %d.\n",
fileline);
} else if (lat1 != BADVAL && lon1 != BADVAL &&
lat2 != BADVAL && lon2 != BADVAL) {
foreach (Waypoint* waypointp, *global_waypoint_list) {
if (waypointp->extra_data) {
ed = (extra_data*) waypointp->extra_data;
} else {
ed = (extra_data*) xcalloc(1, sizeof(*ed));
ed->state = OUTSIDE;
ed->override = 0;
waypointp->extra_data = ed;
}
if (lat2 == waypointp->latitude &&
lon2 == waypointp->longitude) {
ed->override = 1;
}
if (olat != BADVAL && olon != BADVAL &&
olat == lat2 && olon == lon2) {
last = 1;
}
polytest(lat1, lon1, lat2, lon2,
waypointp->latitude,
waypointp->longitude,
&ed->state, first, last);
first = 0;
last = 0;
}
}
if (olat != BADVAL && olon != BADVAL &&
olat == lat2 && olon == lon2) {
olat = BADVAL;
olon = BADVAL;
lat1 = BADVAL;
lon1 = BADVAL;
first = 1;
} else if (lat1 == BADVAL || lon1 == BADVAL) {
olat = lat2;
olon = lon2;
lat1 = lat2;
lon1 = lon2;
} else {
lat1 = lat2;
lon1 = lon2;
}
}
gbfclose(file_in);
foreach (Waypoint* wp, *global_waypoint_list) {
ed = (extra_data*) wp->extra_data;
wp->extra_data = nullptr;
if (ed) {
if (ed->override) {
ed->state = INSIDE;
}
if (((ed->state & INSIDE) == OUTSIDE) == (exclopt == nullptr)) {
waypt_del(wp);
delete wp;
}
xfree(ed);
}
}
}
#endif // FILTERS_ENABLED