PostGIS  2.2.8dev-r@@SVN_REVISION@@

◆ ptarray_locate_point()

double ptarray_locate_point ( const POINTARRAY pa,
const POINT4D pt,
double *  dist,
POINT4D p_located 
)

Definition at line 1303 of file ptarray.c.

References closest_point_on_segment(), distance2d_pt_pt(), distance2d_pt_seg(), getPoint2d_cp(), getPoint4d_p(), LWDEBUG, LWDEBUGF, POINTARRAY::npoints, p2d_same(), ptarray_length_2d(), POINT2D::x, POINT4D::x, POINT2D::y, and POINT4D::y.

Referenced by lwgeom_interpolate_point(), LWGEOM_line_locate_point(), and test_ptarray_locate_point().

1304 {
1305  double mindist=-1;
1306  double tlen, plen;
1307  int t, seg=-1;
1308  POINT4D start4d, end4d, projtmp;
1309  POINT2D proj, p;
1310  const POINT2D *start = NULL, *end = NULL;
1311 
1312  /* Initialize our 2D copy of the input parameter */
1313  p.x = p4d->x;
1314  p.y = p4d->y;
1315 
1316  if ( ! proj4d ) proj4d = &projtmp;
1317 
1318  start = getPoint2d_cp(pa, 0);
1319 
1320  /* If the pointarray has only one point, the nearest point is */
1321  /* just that point */
1322  if ( pa->npoints == 1 )
1323  {
1324  getPoint4d_p(pa, 0, proj4d);
1325  if ( mindistout )
1326  *mindistout = distance2d_pt_pt(&p, start);
1327  return 0.0;
1328  }
1329 
1330  /* Loop through pointarray looking for nearest segment */
1331  for (t=1; t<pa->npoints; t++)
1332  {
1333  double dist;
1334  end = getPoint2d_cp(pa, t);
1335  dist = distance2d_pt_seg(&p, start, end);
1336 
1337  if (t==1 || dist < mindist )
1338  {
1339  mindist = dist;
1340  seg=t-1;
1341  }
1342 
1343  if ( mindist == 0 )
1344  {
1345  LWDEBUG(3, "Breaking on mindist=0");
1346  break;
1347  }
1348 
1349  start = end;
1350  }
1351 
1352  if ( mindistout ) *mindistout = mindist;
1353 
1354  LWDEBUGF(3, "Closest segment: %d", seg);
1355  LWDEBUGF(3, "mindist: %g", mindist);
1356 
1357  /*
1358  * We need to project the
1359  * point on the closest segment.
1360  */
1361  getPoint4d_p(pa, seg, &start4d);
1362  getPoint4d_p(pa, seg+1, &end4d);
1363  closest_point_on_segment(p4d, &start4d, &end4d, proj4d);
1364 
1365  /* Copy 4D values into 2D holder */
1366  proj.x = proj4d->x;
1367  proj.y = proj4d->y;
1368 
1369  LWDEBUGF(3, "Closest segment:%d, npoints:%d", seg, pa->npoints);
1370 
1371  /* For robustness, force 1 when closest point == endpoint */
1372  if ( (seg >= (pa->npoints-2)) && p2d_same(&proj, end) )
1373  {
1374  return 1.0;
1375  }
1376 
1377  LWDEBUGF(3, "Closest point on segment: %g,%g", proj.x, proj.y);
1378 
1379  tlen = ptarray_length_2d(pa);
1380 
1381  LWDEBUGF(3, "tlen %g", tlen);
1382 
1383  /* Location of any point on a zero-length line is 0 */
1384  /* See http://trac.osgeo.org/postgis/ticket/1772#comment:2 */
1385  if ( tlen == 0 ) return 0;
1386 
1387  plen=0;
1388  start = getPoint2d_cp(pa, 0);
1389  for (t=0; t<seg; t++, start=end)
1390  {
1391  end = getPoint2d_cp(pa, t+1);
1392  plen += distance2d_pt_pt(start, end);
1393 
1394  LWDEBUGF(4, "Segment %d made plen %g", t, plen);
1395  }
1396 
1397  plen+=distance2d_pt_pt(&proj, start);
1398 
1399  LWDEBUGF(3, "plen %g, tlen %g", plen, tlen);
1400 
1401  return plen/tlen;
1402 }
int npoints
Definition: liblwgeom.h:355
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:50
double distance2d_pt_pt(const POINT2D *p1, const POINT2D *p2)
The old function nessecary for ptarray_segmentize2d in ptarray.c.
Definition: measures.c:2301
double distance2d_pt_seg(const POINT2D *p, const POINT2D *A, const POINT2D *B)
The old function nessecary for ptarray_segmentize2d in ptarray.c.
Definition: measures.c:2326
double x
Definition: liblwgeom.h:312
int p2d_same(const POINT2D *p1, const POINT2D *p2)
Definition: lwalgorithm.c:35
const POINT2D * getPoint2d_cp(const POINTARRAY *pa, int n)
Returns a POINT2D pointer into the POINTARRAY serialized_ptlist, suitable for reading from...
Definition: lwgeom_api.c:472
void closest_point_on_segment(const POINT4D *p, const POINT4D *A, const POINT4D *B, POINT4D *ret)
Definition: ptarray.c:1255
double y
Definition: liblwgeom.h:312
double ptarray_length_2d(const POINTARRAY *pts)
Find the 2d length of the given POINTARRAY (even if it&#39;s 3d)
Definition: ptarray.c:1645
#define LWDEBUGF(level, msg,...)
Definition: lwgeom_log.h:55
int getPoint4d_p(const POINTARRAY *pa, int n, POINT4D *point)
Definition: lwgeom_api.c:231
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