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/*****************************************************************************
*
* MODULE: Vector library
*
* AUTHOR(S): Original author CERL, probably Dave Gerdes.
* Update to GRASS 5.7 Radim Blazek.
* Update to GRASS 7.0 Markus Metz
*
* PURPOSE: Lower level functions for reading/writing/manipulating vectors.
*
* COPYRIGHT: (C) 2009 by the GRASS Development Team
*
* This program is free software under the GNU General Public
* License (>=v2). Read the file COPYING that comes with GRASS
* for details.
*
*****************************************************************************/
#include <math.h>
#include <grass/vector.h>
#ifndef HUGE_VAL
#define HUGE_VAL 9999999999999.0
#endif
/*
* fills BPoints (must be inited previously) by points from input
* array LPoints
*
* each input LPoints[i] must have at least 2 points
*
* returns number of points or -1 on error
*/
int dig_get_poly_points(int n_lines, struct line_pnts **LPoints,
int *direction, /* line direction: > 0 or < 0 */
struct line_pnts *BPoints)
{
register int i, j, point, start, end, inc;
struct line_pnts *Points;
int n_points;
BPoints->n_points = 0;
if (n_lines < 1) {
return 0;
}
/* Calc required space */
n_points = 0;
for (i = 0; i < n_lines; i++) {
Points = LPoints[i];
n_points += Points->n_points - 1; /* each line from first to last - 1 */
}
n_points++; /* last point */
if (0 > dig_alloc_points(BPoints, n_points))
return (-1);
point = 0;
j = 0;
for (i = 0; i < n_lines; i++) {
Points = LPoints[i];
if (direction[i] > 0) {
start = 0;
end = Points->n_points - 1;
inc = 1;
}
else {
start = Points->n_points - 1;
end = 0;
inc = -1;
}
for (j = start; j != end; j += inc) {
BPoints->x[point] = Points->x[j];
BPoints->y[point] = Points->y[j];
point++;
}
}
/* last point */
BPoints->x[point] = Points->x[j];
BPoints->y[point] = Points->y[j];
BPoints->n_points = n_points;
return (BPoints->n_points);
}
/*
* calculate signed area size for polygon
*
* points must be closed polygon with first point = last point
*
* returns signed area, positive for clockwise, negative for
* counterclockwise, 0 for degenerate
*/
int dig_find_area_poly(struct line_pnts *Points, double *totalarea)
{
int i;
double *x, *y;
double tot_area;
x = Points->x;
y = Points->y;
/* line integral: *Points do not need to be pruned */
/* surveyor's formula is more common, but more prone to
* fp precision limit errors, and *Points would need to be pruned */
tot_area = 0.0;
for (i = 1; i < Points->n_points; i++) {
tot_area += (x[i] - x[i - 1]) * (y[i] + y[i - 1]);
}
*totalarea = 0.5 * tot_area;
return (0);
}
/*
* find orientation of polygon (clockwise or counterclockwise)
* in theory faster than signed area for > 4 vertices, but is not robust
* against special cases
* use dig_find_area_poly instead
*
* points must be closed polygon with first point = last point
*
* this code uses bits and pieces from softSurfer and GEOS
* (C) 2000 softSurfer (www.softsurfer.com)
* (C) 2006 Refractions Research Inc.
*
* copes with partially collapsed boundaries and 8-shaped isles
* the code is long and not much faster than dig_find_area_poly
* it can be written much shorter, but that comes with speed penalty
*
* returns orientation, positive for CW, negative for CCW, 0 for degenerate
*/
double dig_find_poly_orientation(struct line_pnts *Points)
{
unsigned int pnext, pprev, pcur = 0;
unsigned int lastpoint = Points->n_points - 1;
double *x, *y, orientation;
x = Points->x;
y = Points->y;
/* first find leftmost highest vertex of the polygon */
for (pnext = 1; pnext < lastpoint; pnext++) {
if (y[pnext] < y[pcur])
continue;
else if (y[pnext] == y[pcur]) { /* just as high */
if (x[pnext] > x[pcur]) /* but to the right */
continue;
if (x[pnext] ==
x[pcur]) { /* duplicate point, self-intersecting polygon ? */
pprev = (pcur == 0 ? lastpoint - 1 : pcur - 1);
if (y[pnext - 1] < y[pprev])
continue;
}
}
pcur = pnext; /* a new leftmost highest vertex */
}
/* Points are not pruned, so ... */
pnext = pcur;
pprev = pcur;
/* find next distinct point */
do {
if (pnext < lastpoint - 1)
pnext++;
else
pnext = 0;
} while (pnext != pcur && x[pcur] == x[pnext] && y[pcur] == y[pnext]);
/* find previous distinct point */
do {
if (pprev > 0)
pprev--;
else
pprev = lastpoint - 1;
} while (pprev != pcur && x[pcur] == x[pprev] && y[pcur] == y[pprev]);
/* orientation at vertex pcur == signed area for triangle pprev, pcur, pnext
* rather use robust determinant of Olivier Devillers? */
orientation = (x[pnext] - x[pprev]) * (y[pcur] - y[pprev]) -
(x[pcur] - x[pprev]) * (y[pnext] - y[pprev]);
if (orientation)
return orientation;
/* orientation is 0, can happen with dirty boundaries, next check */
/* find rightmost highest vertex of the polygon */
pcur = 0;
for (pnext = 1; pnext < lastpoint; pnext++) {
if (y[pnext] < y[pcur])
continue;
else if (y[pnext] == y[pcur]) { /* just as high */
if (x[pnext] < x[pcur]) /* but to the left */
continue;
if (x[pnext] ==
x[pcur]) { /* duplicate point, self-intersecting polygon ? */
pprev = (pcur == 0 ? lastpoint - 1 : pcur - 1);
if (y[pnext - 1] < y[pprev])
continue;
}
}
pcur = pnext; /* a new rightmost highest vertex */
}
/* Points are not pruned, so ... */
pnext = pcur;
pprev = pcur;
/* find next distinct point */
do {
if (pnext < lastpoint - 1)
pnext++;
else
pnext = 0;
} while (pnext != pcur && x[pcur] == x[pnext] && y[pcur] == y[pnext]);
/* find previous distinct point */
do {
if (pprev > 0)
pprev--;
else
pprev = lastpoint - 1;
} while (pprev != pcur && x[pcur] == x[pprev] && y[pcur] == y[pprev]);
/* orientation at vertex pcur == signed area for triangle pprev, pcur, pnext
* rather use robust determinant of Olivier Devillers? */
orientation = (x[pnext] - x[pprev]) * (y[pcur] - y[pprev]) -
(x[pcur] - x[pprev]) * (y[pnext] - y[pprev]);
if (orientation)
return orientation;
/* orientation is 0, next check */
/* find leftmost lowest vertex of the polygon */
pcur = 0;
for (pnext = 1; pnext < lastpoint; pnext++) {
if (y[pnext] > y[pcur])
continue;
else if (y[pnext] == y[pcur]) { /* just as low */
if (x[pnext] > x[pcur]) /* but to the right */
continue;
if (x[pnext] ==
x[pcur]) { /* duplicate point, self-intersecting polygon ? */
pprev = (pcur == 0 ? lastpoint - 1 : pcur - 1);
if (y[pnext - 1] > y[pprev])
continue;
}
}
pcur = pnext; /* a new leftmost lowest vertex */
}
/* Points are not pruned, so ... */
pnext = pcur;
pprev = pcur;
/* find next distinct point */
do {
if (pnext < lastpoint - 1)
pnext++;
else
pnext = 0;
} while (pnext != pcur && x[pcur] == x[pnext] && y[pcur] == y[pnext]);
/* find previous distinct point */
do {
if (pprev > 0)
pprev--;
else
pprev = lastpoint - 1;
} while (pprev != pcur && x[pcur] == x[pprev] && y[pcur] == y[pprev]);
/* orientation at vertex pcur == signed area for triangle pprev, pcur, pnext
* rather use robust determinant of Olivier Devillers? */
orientation = (x[pnext] - x[pprev]) * (y[pcur] - y[pprev]) -
(x[pcur] - x[pprev]) * (y[pnext] - y[pprev]);
if (orientation)
return orientation;
/* orientation is 0, last check */
/* find rightmost lowest vertex of the polygon */
pcur = 0;
for (pnext = 1; pnext < lastpoint; pnext++) {
if (y[pnext] > y[pcur])
continue;
else if (y[pnext] == y[pcur]) { /* just as low */
if (x[pnext] < x[pcur]) /* but to the left */
continue;
if (x[pnext] ==
x[pcur]) { /* duplicate point, self-intersecting polygon ? */
pprev = (pcur == 0 ? lastpoint - 1 : pcur - 1);
if (y[pnext - 1] > y[pprev])
continue;
}
}
pcur = pnext; /* a new rightmost lowest vertex */
}
/* Points are not pruned, so ... */
pnext = pcur;
pprev = pcur;
/* find next distinct point */
do {
if (pnext < lastpoint - 1)
pnext++;
else
pnext = 0;
} while (pnext != pcur && x[pcur] == x[pnext] && y[pcur] == y[pnext]);
/* find previous distinct point */
do {
if (pprev > 0)
pprev--;
else
pprev = lastpoint - 1;
} while (pprev != pcur && x[pcur] == x[pprev] && y[pcur] == y[pprev]);
/* orientation at vertex pcur == signed area for triangle pprev, pcur, pnext
* rather use robust determinant of Olivier Devillers? */
orientation = (x[pnext] - x[pprev]) * (y[pcur] - y[pprev]) -
(x[pcur] - x[pprev]) * (y[pnext] - y[pprev]);
return orientation; /* 0 for degenerate */
}
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