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postgis/postgis_algo.c
Sandro Santilli 587b27d593 Initial import. 
git-svn-id: http://svn.osgeo.org/postgis/trunk@329 b70326c6-7e19-0410-871a-916f4a2858ee
2003-10-27 10:21:15 +00:00

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/**********************************************************************
* $Id$
*
* PostGIS - Spatial Types for PostgreSQL
* http://postgis.refractions.net
* Copyright 2001-2003 Refractions Research Inc.
*
* This is free software; you can redistribute and/or modify it under
* the terms of the GNU General Public Licence. See the COPYING file.
*
**********************************************************************
* $Log$
* Revision 1.1 2003/10/27 10:21:15 strk
* Initial import.
*
**********************************************************************/
#include "postgres.h"
#include "postgis.h"
/***********************************************************************
* Simple Douglas-Peucker line simplification.
* No checks are done to avoid introduction of self-intersections.
* No topology relations are considered.
*
* --strk@keybit.net;
***********************************************************************/
#define SAMEPOINT(a,b) ((a)->x==(b)->x&&(a)->y==(b)->y&&(a)->z==(b)->z)
#define VERBOSE 0
#if VERBOSE > 0
#undef REPORT_POINTS_REDUCTION
#undef REPORT_RINGS_REDUCTION
#define REPORT_RINGS_ADJUSTMENTS
#endif
#undef CHECK_RING_IS_CLOSE
/*
* Search farthest point from segment p1-p2
* returns squared distance an int pointer
*/
void DP_findsplit(POINT3D *pts, int npts, int p1, int p2,
int *split, double *dist)
{
int k;
POINT3D *pa, *pb, *pk;
double tmp;
#if VERBOSE > 4
elog(NOTICE, "DP_findsplit called");
#endif
*dist = -1;
*split = p1;
if (p1 + 1 < p2)
{
pa = &(pts[p1]);
pb = &(pts[p2]);
#if VERBOSE > 4
elog(NOTICE, "DP_findsplit: P%d(%f,%f) to P%d(%f,%f)",
p1, pa->x, pa->y, p2, pb->x, pb->y);
#endif
for (k=p1+1; k<p2; k++)
{
pk = &(pts[k]);
#if VERBOSE > 4
elog(NOTICE, "DP_findsplit: P%d(%f,%f)", k, pk->x, pk->y);
#endif
/* distance computation */
tmp = distance_pt_seg(pk, pa, pb);
if (tmp > *dist)
{
*dist = tmp; /* record the maximum */
*split = k;
#if VERBOSE > 4
elog(NOTICE, "DP_findsplit: P%d is farthest (%g)", k, *dist);
#endif
}
}
} /* length---should be redone if can == 0 */
else
{
#if VERBOSE > 3
elog(NOTICE, "DP_findsplit: segment too short, no split/no dist");
#endif
}
}
void
DP_simplify(POINT3D *inpts, int inptsn, POINT3D **outpts, int *outptsn, double epsilon)
{
int stack[inptsn]; /* recursion stack */
int sp=-1; /* recursion stack pointer */
int p1, split;
double dist_sq;
double epsilon_sq = epsilon*epsilon;
POINT3D *outpoints;
int numoutpoints=0;
p1 = 0;
stack[++sp] = inptsn-1;
#if VERBOSE > 4
elog(NOTICE, "DP_simplify called");
#endif
outpoints = (POINT3D *)palloc( sizeof(POINT3D) * inptsn);
memcpy(outpoints, inpts, sizeof(POINT3D));
numoutpoints++;
#if VERBOSE > 3
elog(NOTICE, "DP_simplify: added P0 to simplified point array (size 1)");
#endif
do
{
DP_findsplit(inpts, inptsn, p1, stack[sp], &split, &dist_sq);
#if VERBOSE > 3
elog(NOTICE, "DP_simplify: farthest point from P%d-P%d is P%d (dist. %g)", p1, stack[sp], split, sqrt(dist_sq));
#endif
if (dist_sq > epsilon_sq) {
stack[++sp] = split;
} else {
/*
outpoints = repalloc( outpoints, sizeof(POINT3D) * numoutpoints+1 );
if ( outpoints == NULL ) elog(NOTICE, "Out of virtual memory");
*/
memcpy(outpoints+numoutpoints, &(inpts[stack[sp]]),
sizeof(POINT3D));
numoutpoints++;
#if VERBOSE > 3
elog(NOTICE, "DP_simplify: added P%d to simplified point array (size: %d)",
stack[sp], numoutpoints);
#endif
p1 = stack[sp--];
}
#if VERBOSE > 5
elog(NOTICE, "stack pointer = %d", sp);
#endif
}
while (! (sp<0) );
/*
* If we have reduced the number of points realloc
* outpoints array to free up some memory.
* Might be turned on and of with a SAVE_MEMORY define ...
*/
if ( numoutpoints < inptsn )
{
outpoints = (POINT3D *)repalloc(outpoints, sizeof(POINT3D)*numoutpoints);
if ( outpoints == NULL ) {
elog(ERROR, "Out of virtual memory");
}
}
*outpts = outpoints;
*outptsn = numoutpoints;
}
char *
simplify_line3d(LINE3D *iline, double dist)
{
POINT3D *ipts;
POINT3D *opts;
int iptsn, optsn, olinesize;
LINE3D *oline;
ipts = iline->points;
iptsn = iline->npoints;
DP_simplify(ipts, iptsn, &opts, &optsn, dist);
oline = make_line(optsn, opts, &olinesize);
return (char *)oline;
}
char *
simplify_polygon3d(POLYGON3D *ipoly, double dist)
{
POINT3D *ipts;
POINT3D *opts;
int iptsn, optsn, size;
int nrings;
int pts_per_ring[ipoly->nrings];
POLYGON3D *opoly;
int ri;
POINT3D *allpts = NULL;
int allptsn = 0;
int pt_off = 0; /* point offset for each ring */
nrings = 0;
#ifdef REPORT_RINGS_REDUCTION
elog(NOTICE, "simplify_polygon3d: simplifying polygon with %d rings",
ipoly->nrings);
#endif
/* Points start here */
ipts = (POINT3D *) ((char *)&(ipoly->npoints[ipoly->nrings] ));
pt_off=0;
for (ri=0; ri<ipoly->nrings; pt_off += ipoly->npoints[ri++])
{
iptsn = ipoly->npoints[ri];
#ifdef CHECK_RING_IS_CLOSE
if ( ! SAMEPOINT(ipts+pt_off, ipts+pt_off+iptsn-1) )
elog(NOTICE, "First point != Last point");
#endif
DP_simplify(ipts+pt_off, iptsn, &opts, &optsn, dist);
if ( optsn < 2 )
{
/* There as to be an error in DP_simplify */
elog(NOTICE, "DP_simplify returned a <2 pts array");
pfree(opts);
continue;
}
#ifdef CHECK_RING_IS_CLOSE
if ( ! SAMEPOINT(opts, opts+optsn-1) )
elog(NOTICE, "First point != Last point");
#endif
if ( optsn < 4 )
{
pfree(opts);
#ifdef REPORT_RINGS_ADJUSTMENTS
elog(NOTICE, "simplify_polygon3d: ring%d skipped ( <4 pts )", ri);
#endif
if ( ri ) continue;
else break;
}
#ifdef REPORT_POINTS_REDUCTION
elog(NOTICE, "simplify_polygon3d: ring%d simplified from %d to %d points", ri, iptsn, optsn);
#endif
/*
* Add ring to simplified ring array
* (TODO: dinamic allocation of pts_per_ring)
*/
pts_per_ring[nrings++] = optsn;
if ( ! allptsn ) {
allptsn = optsn;
allpts = palloc(sizeof(POINT3D)*allptsn);
memcpy(allpts, opts, sizeof(POINT3D)*optsn);
} else {
allptsn += optsn;
allpts = repalloc(allpts, sizeof(POINT3D)*allptsn);
memcpy(allpts+(allptsn-optsn), opts, sizeof(POINT3D)*optsn);
}
pfree(opts);
if ( ! allpts ) {
elog(NOTICE, "Error allocating memory for all ring points");
return NULL;
}
}
#ifdef REPORT_RINGS_REDUCTION
elog(NOTICE, "simplify_polygon3d: simplified polygon with %d rings", nrings);
#endif
if ( nrings )
{
opoly = make_polygon(nrings, pts_per_ring, allpts, allptsn, &size);
pfree(allpts);
return (char *)opoly;
}
else
{
return NULL;
}
}
char *
simplify_point3d(POINT3D *ipoint, double dist)
{
return (char *)ipoint;
}
PG_FUNCTION_INFO_V1(simplify);
Datum simplify(PG_FUNCTION_ARGS)
{
Datum datum;
BOX3D *bbox;
GEOMETRY *orig_geom;
GEOMETRY *simp_geom = NULL;
char *orig_obj; /* pointer to each object in orig_geom */
char *simp_obj; /* pointer to each simplified object */
int simp_obj_size; /* size of simplified object */
int32 *offsets;
int i;
double dist;
if ( PG_ARGISNULL(0) ) PG_RETURN_NULL();
datum = PG_GETARG_DATUM(0);
orig_geom = (GEOMETRY *)PG_DETOAST_DATUM(datum);
if ( PG_ARGISNULL(1) ) PG_RETURN_NULL();
dist = PG_GETARG_FLOAT8(1);
/*
* Three or more points on a straight line will still collapse!
*/
// if ( dist == 0 ) PG_RETURN_POINTER(orig_geom);
offsets = (int32 *) ( ((char *) &(orig_geom->objType[0] )) +
sizeof(int32) * orig_geom->nobjs );
/*
* Simplify each subobject indipendently.
* No topology relations kept.
*/
for(i=0;i<orig_geom->nobjs; i++)
{
orig_obj = (char *) orig_geom+offsets[i];
if ( orig_geom->objType[i] == LINETYPE )
{
simp_obj = simplify_line3d((LINE3D *)orig_obj, dist);
}
else if ( orig_geom->objType[i] == POLYGONTYPE )
{
simp_obj = simplify_polygon3d((POLYGON3D *)orig_obj, dist);
}
else if ( orig_geom->objType[i] == POINTTYPE )
{
simp_obj = simplify_point3d((POINT3D *)orig_obj, dist);
}
else
{
elog(NOTICE, "Unknown geometry type");
PG_RETURN_NULL();
}
/* Simplified object degenerated to empty set */
if ( ! simp_obj ) continue;
/* Get size of simplified object */
simp_obj_size = size_subobject(simp_obj, orig_geom->objType[i]);
/* Create one-object geometry (will add objects later) */
if ( simp_geom == NULL )
{
simp_geom = make_oneobj_geometry(
simp_obj_size, simp_obj, orig_geom->objType[i],
orig_geom->is3d, orig_geom->SRID, orig_geom->scale,
orig_geom->offsetX, orig_geom->offsetY);
}
/* Add object to already initialized geometry */
else
{
simp_geom = add_to_geometry(
simp_geom, simp_obj_size, simp_obj,
orig_geom->objType[i] );
}
/* Error in simplified geometry construction */
if ( ! simp_geom )
{
elog(ERROR, "geometry construction failed at iteration %d", i);
PG_RETURN_NULL();
}
}
if ( simp_geom == NULL ) PG_RETURN_NULL();
/* Calculate the bounding box */
bbox = bbox_of_geometry(simp_geom);
memcpy(&(simp_geom->bvol), bbox, sizeof(BOX3D));
pfree(bbox);
simp_geom->type = orig_geom->type;
PG_RETURN_POINTER(simp_geom);
}
/***********************************************************************
* --strk@keybit.net;
***********************************************************************/
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