PostGIS  2.5.2dev-r@@SVN_REVISION@@

◆ ptarray_substring()

POINTARRAY* ptarray_substring ( POINTARRAY pa,
double  d1,
double  d2,
double  tolerance 
)

start location (distance from start / total distance) end location (distance from start / total distance)

Parameters
tolerancesnap to vertices at locations < tolerance away from given ones

Definition at line 1060 of file ptarray.c.

References distance2d_pt_pt(), POINTARRAY::flags, FLAGS_GET_M, FLAGS_GET_Z, getPoint4d_p(), interpolate_point4d(), LW_FALSE, LWDEBUG, LWDEBUGF, POINT4D::m, POINTARRAY::npoints, ptarray_append_point(), ptarray_construct_empty(), ptarray_length_2d(), POINT4D::x, POINT4D::y, and POINT4D::z.

Referenced by LWGEOM_line_substring().

1061 {
1062  POINTARRAY *dpa;
1063  POINT4D pt;
1064  POINT4D p1, p2;
1065  POINT4D *p1ptr=&p1; /* don't break strict-aliasing rule */
1066  POINT4D *p2ptr=&p2;
1067  int nsegs, i;
1068  double length, slength, tlength;
1069  int state = 0; /* 0=before, 1=inside */
1070 
1071  /*
1072  * Create a dynamic pointarray with an initial capacity
1073  * equal to full copy of input points
1074  */
1076 
1077  /* Compute total line length */
1078  length = ptarray_length_2d(ipa);
1079 
1080 
1081  LWDEBUGF(3, "Total length: %g", length);
1082 
1083 
1084  /* Get 'from' and 'to' lengths */
1085  from = length*from;
1086  to = length*to;
1087 
1088 
1089  LWDEBUGF(3, "From/To: %g/%g", from, to);
1090 
1091 
1092  tlength = 0;
1093  getPoint4d_p(ipa, 0, &p1);
1094  nsegs = ipa->npoints - 1;
1095  for ( i = 0; i < nsegs; i++ )
1096  {
1097  double dseg;
1098 
1099  getPoint4d_p(ipa, i+1, &p2);
1100 
1101 
1102  LWDEBUGF(3 ,"Segment %d: (%g,%g,%g,%g)-(%g,%g,%g,%g)",
1103  i, p1.x, p1.y, p1.z, p1.m, p2.x, p2.y, p2.z, p2.m);
1104 
1105 
1106  /* Find the length of this segment */
1107  slength = distance2d_pt_pt((POINT2D *)p1ptr, (POINT2D *)p2ptr);
1108 
1109  /*
1110  * We are before requested start.
1111  */
1112  if ( state == 0 ) /* before */
1113  {
1114 
1115  LWDEBUG(3, " Before start");
1116 
1117  if ( fabs ( from - ( tlength + slength ) ) <= tolerance )
1118  {
1119 
1120  LWDEBUG(3, " Second point is our start");
1121 
1122  /*
1123  * Second point is our start
1124  */
1125  ptarray_append_point(dpa, &p2, LW_FALSE);
1126  state=1; /* we're inside now */
1127  goto END;
1128  }
1129 
1130  else if ( fabs(from - tlength) <= tolerance )
1131  {
1132 
1133  LWDEBUG(3, " First point is our start");
1134 
1135  /*
1136  * First point is our start
1137  */
1138  ptarray_append_point(dpa, &p1, LW_FALSE);
1139 
1140  /*
1141  * We're inside now, but will check
1142  * 'to' point as well
1143  */
1144  state=1;
1145  }
1146 
1147  /*
1148  * Didn't reach the 'from' point,
1149  * nothing to do
1150  */
1151  else if ( from > tlength + slength ) goto END;
1152 
1153  else /* tlength < from < tlength+slength */
1154  {
1155 
1156  LWDEBUG(3, " Seg contains first point");
1157 
1158  /*
1159  * Our start is between first and
1160  * second point
1161  */
1162  dseg = (from - tlength) / slength;
1163 
1164  interpolate_point4d(&p1, &p2, &pt, dseg);
1165 
1166  ptarray_append_point(dpa, &pt, LW_FALSE);
1167 
1168  /*
1169  * We're inside now, but will check
1170  * 'to' point as well
1171  */
1172  state=1;
1173  }
1174  }
1175 
1176  if ( state == 1 ) /* inside */
1177  {
1178 
1179  LWDEBUG(3, " Inside");
1180 
1181  /*
1182  * 'to' point is our second point.
1183  */
1184  if ( fabs(to - ( tlength + slength ) ) <= tolerance )
1185  {
1186 
1187  LWDEBUG(3, " Second point is our end");
1188 
1189  ptarray_append_point(dpa, &p2, LW_FALSE);
1190  break; /* substring complete */
1191  }
1192 
1193  /*
1194  * 'to' point is our first point.
1195  * (should only happen if 'to' is 0)
1196  */
1197  else if ( fabs(to - tlength) <= tolerance )
1198  {
1199 
1200  LWDEBUG(3, " First point is our end");
1201 
1202  ptarray_append_point(dpa, &p1, LW_FALSE);
1203 
1204  break; /* substring complete */
1205  }
1206 
1207  /*
1208  * Didn't reach the 'end' point,
1209  * just copy second point
1210  */
1211  else if ( to > tlength + slength )
1212  {
1213  ptarray_append_point(dpa, &p2, LW_FALSE);
1214  goto END;
1215  }
1216 
1217  /*
1218  * 'to' point falls on this segment
1219  * Interpolate and break.
1220  */
1221  else if ( to < tlength + slength )
1222  {
1223 
1224  LWDEBUG(3, " Seg contains our end");
1225 
1226  dseg = (to - tlength) / slength;
1227  interpolate_point4d(&p1, &p2, &pt, dseg);
1228 
1229  ptarray_append_point(dpa, &pt, LW_FALSE);
1230 
1231  break;
1232  }
1233 
1234  else
1235  {
1236  LWDEBUG(3, "Unhandled case");
1237  }
1238  }
1239 
1240 
1241 END:
1242 
1243  tlength += slength;
1244  memcpy(&p1, &p2, sizeof(POINT4D));
1245  }
1246 
1247  LWDEBUGF(3, "Out of loop, ptarray has %d points", dpa->npoints);
1248 
1249  return dpa;
1250 }
double x
Definition: liblwgeom.h:354
double m
Definition: liblwgeom.h:354
#define LWDEBUG(level, msg)
Definition: lwgeom_log.h:83
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_FALSE, then a duplicate point will not be added.
Definition: ptarray.c:156
double distance2d_pt_pt(const POINT2D *p1, const POINT2D *p2)
Definition: measures.c:2313
void interpolate_point4d(const POINT4D *A, const POINT4D *B, POINT4D *I, double F)
Find interpolation point I between point A and point B so that the len(AI) == len(AB)*F and I falls o...
Definition: lwgeom_api.c:714
#define LW_FALSE
Definition: liblwgeom.h:76
uint8_t flags
Definition: liblwgeom.h:371
#define FLAGS_GET_Z(flags)
Macros for manipulating the &#39;flags&#39; byte.
Definition: liblwgeom.h:139
double ptarray_length_2d(const POINTARRAY *pts)
Find the 2d length of the given POINTARRAY (even if it&#39;s 3d)
Definition: ptarray.c:1689
double z
Definition: liblwgeom.h:354
int getPoint4d_p(const POINTARRAY *pa, uint32_t n, POINT4D *point)
Definition: lwgeom_api.c:123
POINTARRAY * ptarray_construct_empty(char hasz, char hasm, uint32_t maxpoints)
Create a new POINTARRAY with no points.
Definition: ptarray.c:70
#define FLAGS_GET_M(flags)
Definition: liblwgeom.h:140
double y
Definition: liblwgeom.h:354
#define LWDEBUGF(level, msg,...)
Definition: lwgeom_log.h:88
uint32_t npoints
Definition: liblwgeom.h:373
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