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Improve robustness of ptarray_isccw (see #1302)

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git-svn-id: http://svn.osgeo.org/postgis/trunk@8198 b70326c6-7e19-0410-871a-916f4a2858ee
This commit is contained in:
Sandro Santilli 2011-11-21 08:08:18 +00:00
parent 243df1584e
commit 50593de781
1 changed files with 9 additions and 2 deletions
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11
liblwgeom/lwgeom_api.c
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@ -556,14 +556,21 @@ ptarray_isccw(const POINTARRAY *pa)
{
int i;
double area = 0;
POINT2D p1, p2;
POINT2D p1, p2, p0;
if ( pa->npoints == 0 ) return 0;
getPoint2d_p(pa, 0, &p1);
p0 = p1;
p1.x -= p0.x; p1.y -= p0.y;
for (i=0; i<pa->npoints-1; i++)
{
getPoint2d_p(pa, i, &p1);
getPoint2d_p(pa, i+1, &p2);
p2.x -= p0.x; p2.y -= p0.y;
area += (p1.y * p2.x) - (p1.x * p2.y);
p1 = p2;
}
/* lwnotice("Signed area: %.16g", area); */
if ( area > 0 ) return 0;
else return 1;
}