LWGEOM* pta_desegmentize(POINTARRAY *points, int type, int srid) { int i = 0, j, k; POINT4D a1, a2, a3, b; char *edges_in_arcs; int found_arc = LW_FALSE; int current_arc = 1; int num_edges; int edge_type = -1; int start, end; LWCOLLECTION *outcol; /* Die on null input */ if ( ! points ) lwerror("pta_desegmentize called with null pointarray"); /* Null on empty input? */ if ( points->npoints == 0 ) return NULL; /* We can't desegmentize anything shorter than four points */ if ( points->npoints < 4 ) { /* Return a linestring here*/ lwerror("pta_desegmentize needs implementation for npoints < 4"); } /* Allocate our result array of vertices that are part of arcs */ num_edges = points->npoints - 1; edges_in_arcs = lwalloc(num_edges); memset(edges_in_arcs, 0, num_edges); /* We make a candidate arc of the first two edges, */ /* And then see if the next edge follows it */ while( i < num_edges-2 ) { found_arc = LW_FALSE; /* Make candidate arc */ getPoint4d_p(points, i , &a1); getPoint4d_p(points, i+1, &a2); getPoint4d_p(points, i+2, &a3); for( j = i+3; j < num_edges+1; j++ ) { LWDEBUGF(4, "i=%d, j=%d", i, j); getPoint4d_p(points, j, &b); /* Does this point fall on our candidate arc? */ if ( pt_continues_arc(&a1, &a2, &a3, &b) ) { /* Yes. Mark this edge and the two preceding it as arc components */ LWDEBUGF(4, "pt_continues_arc #%d", current_arc); found_arc = LW_TRUE; for ( k = j-1; k > j-4; k-- ) edges_in_arcs[k] = current_arc; } else { /* No. So we're done with this candidate arc */ LWDEBUG(4, "pt_continues_arc = false"); current_arc++; break; } } /* Jump past all the edges that were added to the arc */ if ( found_arc ) { i = j-1; } else { /* Mark this edge as a linear edge */ edges_in_arcs[i] = 0; i = i+1; } } #if POSTGIS_DEBUG_LEVEL > 3 { char *edgestr = lwalloc(num_edges+1); for ( i = 0; i < num_edges; i++ ) { if ( edges_in_arcs[i] ) edgestr[i] = 48 + edges_in_arcs[i]; else edgestr[i] = '.'; } edgestr[num_edges] = 0; LWDEBUGF(3, "edge pattern %s", edgestr); lwfree(edgestr); } #endif start = 0; edge_type = edges_in_arcs[0]; outcol = lwcollection_construct_empty(COMPOUNDTYPE, srid, ptarray_has_z(points), ptarray_has_m(points)); for( i = 1; i < num_edges; i++ ) { if( edge_type != edges_in_arcs[i] ) { end = i - 1; lwcollection_add_lwgeom(outcol, geom_from_pa(points, srid, edge_type, start, end)); start = i; edge_type = edges_in_arcs[i]; } } /* Roll out last item */ end = num_edges - 1; lwcollection_add_lwgeom(outcol, geom_from_pa(points, srid, edge_type, start, end)); /* Strip down to singleton if only one entry */ if ( outcol->ngeoms == 1 ) { LWGEOM *outgeom = outcol->geoms[0]; lwfree(outcol); return outgeom; } return lwcollection_as_lwgeom(outcol); }
LWGEOM* pta_unstroke(const POINTARRAY *points, int type, int srid) { int i = 0, j, k; POINT4D a1, a2, a3, b; POINT4D first, center; char *edges_in_arcs; int found_arc = LW_FALSE; int current_arc = 1; int num_edges; int edge_type; /* non-zero if edge is part of an arc */ int start, end; LWCOLLECTION *outcol; /* Minimum number of edges, per quadrant, required to define an arc */ const unsigned int min_quad_edges = 2; /* Die on null input */ if ( ! points ) lwerror("pta_unstroke called with null pointarray"); /* Null on empty input? */ if ( points->npoints == 0 ) return NULL; /* We can't desegmentize anything shorter than four points */ if ( points->npoints < 4 ) { /* Return a linestring here*/ lwerror("pta_unstroke needs implementation for npoints < 4"); } /* Allocate our result array of vertices that are part of arcs */ num_edges = points->npoints - 1; edges_in_arcs = lwalloc(num_edges + 1); memset(edges_in_arcs, 0, num_edges + 1); /* We make a candidate arc of the first two edges, */ /* And then see if the next edge follows it */ while( i < num_edges-2 ) { unsigned int arc_edges; double num_quadrants; double angle; found_arc = LW_FALSE; /* Make candidate arc */ getPoint4d_p(points, i , &a1); getPoint4d_p(points, i+1, &a2); getPoint4d_p(points, i+2, &a3); memcpy(&first, &a1, sizeof(POINT4D)); for( j = i+3; j < num_edges+1; j++ ) { LWDEBUGF(4, "i=%d, j=%d", i, j); getPoint4d_p(points, j, &b); /* Does this point fall on our candidate arc? */ if ( pt_continues_arc(&a1, &a2, &a3, &b) ) { /* Yes. Mark this edge and the two preceding it as arc components */ LWDEBUGF(4, "pt_continues_arc #%d", current_arc); found_arc = LW_TRUE; for ( k = j-1; k > j-4; k-- ) edges_in_arcs[k] = current_arc; } else { /* No. So we're done with this candidate arc */ LWDEBUG(4, "pt_continues_arc = false"); current_arc++; break; } memcpy(&a1, &a2, sizeof(POINT4D)); memcpy(&a2, &a3, sizeof(POINT4D)); memcpy(&a3, &b, sizeof(POINT4D)); } /* Jump past all the edges that were added to the arc */ if ( found_arc ) { /* Check if an arc was composed by enough edges to be * really considered an arc * See http://trac.osgeo.org/postgis/ticket/2420 */ arc_edges = j - 1 - i; LWDEBUGF(4, "arc defined by %d edges found", arc_edges); if ( first.x == b.x && first.y == b.y ) { LWDEBUG(4, "arc is a circle"); num_quadrants = 4; } else { lw_arc_center((POINT2D*)&first, (POINT2D*)&b, (POINT2D*)&a1, (POINT2D*)¢er); angle = lw_arc_angle((POINT2D*)&first, (POINT2D*)¢er, (POINT2D*)&b); int p2_side = lw_segment_side((POINT2D*)&first, (POINT2D*)&a1, (POINT2D*)&b); if ( p2_side >= 0 ) angle = -angle; if ( angle < 0 ) angle = 2 * M_PI + angle; num_quadrants = ( 4 * angle ) / ( 2 * M_PI ); LWDEBUGF(4, "arc angle (%g %g, %g %g, %g %g) is %g (side is %d), quandrants:%g", first.x, first.y, center.x, center.y, b.x, b.y, angle, p2_side, num_quadrants); } /* a1 is first point, b is last point */ if ( arc_edges < min_quad_edges * num_quadrants ) { LWDEBUGF(4, "Not enough edges for a %g quadrants arc, %g needed", num_quadrants, min_quad_edges * num_quadrants); for ( k = j-1; k >= i; k-- ) edges_in_arcs[k] = 0; } i = j-1; } else { /* Mark this edge as a linear edge */ edges_in_arcs[i] = 0; i = i+1; } } #if POSTGIS_DEBUG_LEVEL > 3 { char *edgestr = lwalloc(num_edges+1); for ( i = 0; i < num_edges; i++ ) { if ( edges_in_arcs[i] ) edgestr[i] = 48 + edges_in_arcs[i]; else edgestr[i] = '.'; } edgestr[num_edges] = 0; LWDEBUGF(3, "edge pattern %s", edgestr); lwfree(edgestr); } #endif start = 0; edge_type = edges_in_arcs[0]; outcol = lwcollection_construct_empty(COMPOUNDTYPE, srid, ptarray_has_z(points), ptarray_has_m(points)); for( i = 1; i < num_edges; i++ ) { if( edge_type != edges_in_arcs[i] ) { end = i - 1; lwcollection_add_lwgeom(outcol, geom_from_pa(points, srid, edge_type, start, end)); start = i; edge_type = edges_in_arcs[i]; } } lwfree(edges_in_arcs); /* not needed anymore */ /* Roll out last item */ end = num_edges - 1; lwcollection_add_lwgeom(outcol, geom_from_pa(points, srid, edge_type, start, end)); /* Strip down to singleton if only one entry */ if ( outcol->ngeoms == 1 ) { LWGEOM *outgeom = outcol->geoms[0]; outcol->ngeoms = 0; lwcollection_free(outcol); return outgeom; } return lwcollection_as_lwgeom(outcol); }