PostGIS  3.0.0dev-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 1047 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().

1048 {
1049  POINTARRAY *dpa;
1050  POINT4D pt;
1051  POINT4D p1, p2;
1052  POINT4D *p1ptr=&p1; /* don't break strict-aliasing rule */
1053  POINT4D *p2ptr=&p2;
1054  int nsegs, i;
1055  double length, slength, tlength;
1056  int state = 0; /* 0=before, 1=inside */
1057 
1058  /*
1059  * Create a dynamic pointarray with an initial capacity
1060  * equal to full copy of input points
1061  */
1063 
1064  /* Compute total line length */
1065  length = ptarray_length_2d(ipa);
1066 
1067 
1068  LWDEBUGF(3, "Total length: %g", length);
1069 
1070 
1071  /* Get 'from' and 'to' lengths */
1072  from = length*from;
1073  to = length*to;
1074 
1075 
1076  LWDEBUGF(3, "From/To: %g/%g", from, to);
1077 
1078 
1079  tlength = 0;
1080  getPoint4d_p(ipa, 0, &p1);
1081  nsegs = ipa->npoints - 1;
1082  for ( i = 0; i < nsegs; i++ )
1083  {
1084  double dseg;
1085 
1086  getPoint4d_p(ipa, i+1, &p2);
1087 
1088 
1089  LWDEBUGF(3 ,"Segment %d: (%g,%g,%g,%g)-(%g,%g,%g,%g)",
1090  i, p1.x, p1.y, p1.z, p1.m, p2.x, p2.y, p2.z, p2.m);
1091 
1092 
1093  /* Find the length of this segment */
1094  slength = distance2d_pt_pt((POINT2D *)p1ptr, (POINT2D *)p2ptr);
1095 
1096  /*
1097  * We are before requested start.
1098  */
1099  if ( state == 0 ) /* before */
1100  {
1101 
1102  LWDEBUG(3, " Before start");
1103 
1104  if ( fabs ( from - ( tlength + slength ) ) <= tolerance )
1105  {
1106 
1107  LWDEBUG(3, " Second point is our start");
1108 
1109  /*
1110  * Second point is our start
1111  */
1112  ptarray_append_point(dpa, &p2, LW_FALSE);
1113  state=1; /* we're inside now */
1114  goto END;
1115  }
1116 
1117  else if ( fabs(from - tlength) <= tolerance )
1118  {
1119 
1120  LWDEBUG(3, " First point is our start");
1121 
1122  /*
1123  * First point is our start
1124  */
1125  ptarray_append_point(dpa, &p1, LW_FALSE);
1126 
1127  /*
1128  * We're inside now, but will check
1129  * 'to' point as well
1130  */
1131  state=1;
1132  }
1133 
1134  /*
1135  * Didn't reach the 'from' point,
1136  * nothing to do
1137  */
1138  else if ( from > tlength + slength ) goto END;
1139 
1140  else /* tlength < from < tlength+slength */
1141  {
1142 
1143  LWDEBUG(3, " Seg contains first point");
1144 
1145  /*
1146  * Our start is between first and
1147  * second point
1148  */
1149  dseg = (from - tlength) / slength;
1150 
1151  interpolate_point4d(&p1, &p2, &pt, dseg);
1152 
1153  ptarray_append_point(dpa, &pt, LW_FALSE);
1154 
1155  /*
1156  * We're inside now, but will check
1157  * 'to' point as well
1158  */
1159  state=1;
1160  }
1161  }
1162 
1163  if ( state == 1 ) /* inside */
1164  {
1165 
1166  LWDEBUG(3, " Inside");
1167 
1168  /*
1169  * 'to' point is our second point.
1170  */
1171  if ( fabs(to - ( tlength + slength ) ) <= tolerance )
1172  {
1173 
1174  LWDEBUG(3, " Second point is our end");
1175 
1176  ptarray_append_point(dpa, &p2, LW_FALSE);
1177  break; /* substring complete */
1178  }
1179 
1180  /*
1181  * 'to' point is our first point.
1182  * (should only happen if 'to' is 0)
1183  */
1184  else if ( fabs(to - tlength) <= tolerance )
1185  {
1186 
1187  LWDEBUG(3, " First point is our end");
1188 
1189  ptarray_append_point(dpa, &p1, LW_FALSE);
1190 
1191  break; /* substring complete */
1192  }
1193 
1194  /*
1195  * Didn't reach the 'end' point,
1196  * just copy second point
1197  */
1198  else if ( to > tlength + slength )
1199  {
1200  ptarray_append_point(dpa, &p2, LW_FALSE);
1201  goto END;
1202  }
1203 
1204  /*
1205  * 'to' point falls on this segment
1206  * Interpolate and break.
1207  */
1208  else if ( to < tlength + slength )
1209  {
1210 
1211  LWDEBUG(3, " Seg contains our end");
1212 
1213  dseg = (to - tlength) / slength;
1214  interpolate_point4d(&p1, &p2, &pt, dseg);
1215 
1216  ptarray_append_point(dpa, &pt, LW_FALSE);
1217 
1218  break;
1219  }
1220 
1221  else
1222  {
1223  LWDEBUG(3, "Unhandled case");
1224  }
1225  }
1226 
1227 
1228 END:
1229 
1230  tlength += slength;
1231  memcpy(&p1, &p2, sizeof(POINT4D));
1232  }
1233 
1234  LWDEBUGF(3, "Out of loop, ptarray has %d points", dpa->npoints);
1235 
1236  return dpa;
1237 }
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:144
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:683
#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:1676
double z
Definition: liblwgeom.h:354
int getPoint4d_p(const POINTARRAY *pa, uint32_t n, POINT4D *point)
Definition: lwgeom_api.c:112
POINTARRAY * ptarray_construct_empty(char hasz, char hasm, uint32_t maxpoints)
Create a new POINTARRAY with no points.
Definition: ptarray.c:58
#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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