PostGIS  2.1.10dev-r@@SVN_REVISION@@
POINTARRAY* ptarray_segmentize2d ( const POINTARRAY ipa,
double  dist 
)

Returns a modified POINTARRAY so that no segment is longer than the given distance (computed using 2d).

Every input point is kept. Z and M values for added points (if needed) are set to 0.

Definition at line 381 of file ptarray.c.

References distance2d_pt_pt(), POINTARRAY::flags, FLAGS_GET_M, FLAGS_GET_Z, getPoint4d_p(), LW_FALSE, LW_TRUE, POINT4D::m, POINTARRAY::npoints, ptarray_append_point(), ptarray_construct_empty(), POINT4D::x, POINT4D::y, and POINT4D::z.

Referenced by lwline_segmentize2d(), and lwpoly_segmentize2d().

382 {
383  double segdist;
384  POINT4D p1, p2;
385  POINT4D pbuf;
386  POINTARRAY *opa;
387  int ipoff=0; /* input point offset */
388  int hasz = FLAGS_GET_Z(ipa->flags);
389  int hasm = FLAGS_GET_M(ipa->flags);
390 
391  pbuf.x = pbuf.y = pbuf.z = pbuf.m = 0;
392 
393  /* Initial storage */
394  opa = ptarray_construct_empty(hasz, hasm, ipa->npoints);
395 
396  /* Add first point */
397  getPoint4d_p(ipa, ipoff, &p1);
398  ptarray_append_point(opa, &p1, LW_FALSE);
399 
400  ipoff++;
401 
402  while (ipoff<ipa->npoints)
403  {
404  /*
405  * We use these pointers to avoid
406  * "strict-aliasing rules break" warning raised
407  * by gcc (3.3 and up).
408  *
409  * It looks that casting a variable address (also
410  * referred to as "type-punned pointer")
411  * breaks those "strict" rules.
412  *
413  */
414  POINT4D *p1ptr=&p1, *p2ptr=&p2;
415 
416  getPoint4d_p(ipa, ipoff, &p2);
417 
418  segdist = distance2d_pt_pt((POINT2D *)p1ptr, (POINT2D *)p2ptr);
419 
420  if (segdist > dist) /* add an intermediate point */
421  {
422  pbuf.x = p1.x + (p2.x-p1.x)/segdist * dist;
423  pbuf.y = p1.y + (p2.y-p1.y)/segdist * dist;
424  if( hasz )
425  pbuf.z = p1.z + (p2.z-p1.z)/segdist * dist;
426  if( hasm )
427  pbuf.m = p1.m + (p2.m-p1.m)/segdist * dist;
428  ptarray_append_point(opa, &pbuf, LW_FALSE);
429  p1 = pbuf;
430  }
431  else /* copy second point */
432  {
433  ptarray_append_point(opa, &p2, (ipa->npoints==2)?LW_TRUE:LW_FALSE);
434  p1 = p2;
435  ipoff++;
436  }
437  }
438 
439  return opa;
440 }
double x
Definition: liblwgeom.h:308
double m
Definition: liblwgeom.h:308
int npoints
Definition: liblwgeom.h:327
int ptarray_append_point(POINTARRAY *pa, const POINT4D *pt, int repeated_points)
Append a point to the end of an existing POINTARRAY If allow_duplicate is LW_TRUE, then a duplicate point will not be added.
Definition: ptarray.c:141
double distance2d_pt_pt(const POINT2D *p1, const POINT2D *p2)
The old function nessecary for ptarray_segmentize2d in ptarray.c.
Definition: measures.c:2123
#define LW_FALSE
Definition: liblwgeom.h:52
uint8_t flags
Definition: liblwgeom.h:325
#define LW_TRUE
Return types for functions with status returns.
Definition: liblwgeom.h:51
#define FLAGS_GET_Z(flags)
Macros for manipulating the 'flags' byte.
Definition: liblwgeom.h:106
double z
Definition: liblwgeom.h:308
POINTARRAY * ptarray_construct_empty(char hasz, char hasm, uint32_t maxpoints)
Create a new POINTARRAY with no points.
Definition: ptarray.c:57
#define FLAGS_GET_M(flags)
Definition: liblwgeom.h:107
double y
Definition: liblwgeom.h:308
int getPoint4d_p(const POINTARRAY *pa, int n, POINT4D *point)
Definition: lwgeom_api.c:217

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