PostGIS  2.3.8dev-r@@SVN_REVISION@@

◆ ptarray_locate_point()

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

Definition at line 1310 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().

1311 {
1312  double mindist=-1;
1313  double tlen, plen;
1314  int t, seg=-1;
1315  POINT4D start4d, end4d, projtmp;
1316  POINT2D proj, p;
1317  const POINT2D *start = NULL, *end = NULL;
1318 
1319  /* Initialize our 2D copy of the input parameter */
1320  p.x = p4d->x;
1321  p.y = p4d->y;
1322 
1323  if ( ! proj4d ) proj4d = &projtmp;
1324 
1325  start = getPoint2d_cp(pa, 0);
1326 
1327  /* If the pointarray has only one point, the nearest point is */
1328  /* just that point */
1329  if ( pa->npoints == 1 )
1330  {
1331  getPoint4d_p(pa, 0, proj4d);
1332  if ( mindistout )
1333  *mindistout = distance2d_pt_pt(&p, start);
1334  return 0.0;
1335  }
1336 
1337  /* Loop through pointarray looking for nearest segment */
1338  for (t=1; t<pa->npoints; t++)
1339  {
1340  double dist;
1341  end = getPoint2d_cp(pa, t);
1342  dist = distance2d_pt_seg(&p, start, end);
1343 
1344  if (t==1 || dist < mindist )
1345  {
1346  mindist = dist;
1347  seg=t-1;
1348  }
1349 
1350  if ( mindist == 0 )
1351  {
1352  LWDEBUG(3, "Breaking on mindist=0");
1353  break;
1354  }
1355 
1356  start = end;
1357  }
1358 
1359  if ( mindistout ) *mindistout = mindist;
1360 
1361  LWDEBUGF(3, "Closest segment: %d", seg);
1362  LWDEBUGF(3, "mindist: %g", mindist);
1363 
1364  /*
1365  * We need to project the
1366  * point on the closest segment.
1367  */
1368  getPoint4d_p(pa, seg, &start4d);
1369  getPoint4d_p(pa, seg+1, &end4d);
1370  closest_point_on_segment(p4d, &start4d, &end4d, proj4d);
1371 
1372  /* Copy 4D values into 2D holder */
1373  proj.x = proj4d->x;
1374  proj.y = proj4d->y;
1375 
1376  LWDEBUGF(3, "Closest segment:%d, npoints:%d", seg, pa->npoints);
1377 
1378  /* For robustness, force 1 when closest point == endpoint */
1379  if ( (seg >= (pa->npoints-2)) && p2d_same(&proj, end) )
1380  {
1381  return 1.0;
1382  }
1383 
1384  LWDEBUGF(3, "Closest point on segment: %g,%g", proj.x, proj.y);
1385 
1386  tlen = ptarray_length_2d(pa);
1387 
1388  LWDEBUGF(3, "tlen %g", tlen);
1389 
1390  /* Location of any point on a zero-length line is 0 */
1391  /* See http://trac.osgeo.org/postgis/ticket/1772#comment:2 */
1392  if ( tlen == 0 ) return 0;
1393 
1394  plen=0;
1395  start = getPoint2d_cp(pa, 0);
1396  for (t=0; t<seg; t++, start=end)
1397  {
1398  end = getPoint2d_cp(pa, t+1);
1399  plen += distance2d_pt_pt(start, end);
1400 
1401  LWDEBUGF(4, "Segment %d made plen %g", t, plen);
1402  }
1403 
1404  plen+=distance2d_pt_pt(&proj, start);
1405 
1406  LWDEBUGF(3, "plen %g, tlen %g", plen, tlen);
1407 
1408  return plen/tlen;
1409 }
int npoints
Definition: liblwgeom.h:370
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:83
double distance2d_pt_pt(const POINT2D *p1, const POINT2D *p2)
The old function nessecary for ptarray_segmentize2d in ptarray.c.
Definition: measures.c:2316
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:2341
double x
Definition: liblwgeom.h:327
int p2d_same(const POINT2D *p1, const POINT2D *p2)
Definition: lwalgorithm.c:49
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:485
void closest_point_on_segment(const POINT4D *p, const POINT4D *A, const POINT4D *B, POINT4D *ret)
Definition: ptarray.c:1262
double y
Definition: liblwgeom.h:327
double ptarray_length_2d(const POINTARRAY *pts)
Find the 2d length of the given POINTARRAY (even if it&#39;s 3d)
Definition: ptarray.c:1652
#define LWDEBUGF(level, msg,...)
Definition: lwgeom_log.h:88
int getPoint4d_p(const POINTARRAY *pa, int n, POINT4D *point)
Definition: lwgeom_api.c:244
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