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Added interpolate_point4d() general function in API

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git-svn-id: http://svn.osgeo.org/postgis/trunk@2287 b70326c6-7e19-0410-871a-916f4a2858ee
This commit is contained in:
Sandro Santilli 2006-01-19 18:16:17 +00:00
parent 3fdcc7037b
commit a4e5fabee5
2 changed files with 32 additions and 2 deletions
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2
lwgeom/liblwgeom.h
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@ -934,6 +934,8 @@ extern int lwpoly_compute_box2d_p(LWPOLY *poly, BOX2DFLOAT4 *box);
extern int lwcollection_compute_box2d_p(LWCOLLECTION *col, BOX2DFLOAT4 *box);
extern BOX2DFLOAT4 *lwgeom_compute_box2d(LWGEOM *lwgeom);
extern void interpolate_point4d(POINT4D *A, POINT4D *B, POINT4D *I, double F);
/* return alloced memory */
extern BOX2DFLOAT4 *box2d_union(BOX2DFLOAT4 *b1, BOX2DFLOAT4 *b2);

32
lwgeom/lwgeom_api.c
View file

@ -475,12 +475,11 @@ getPoint4d_p(const POINTARRAY *pa, int n, POINT4D *op)
int zmflag;
#if PARANOIA_LEVEL > 0
if ( ! pa ) return 0;
if ( ! pa ) lwerror("getPoint4d_p: NULL pointarray");
if ( (n<0) || (n>=pa->npoints))
{
lwerror("getPoint4d_p: point offset out of range");
return 0; /*error */
}
#endif
@ -2135,3 +2134,32 @@ parse_lwgeom_wkt(char *wkt_input)
return serialized_form;
}
/*
* Find interpolation point I
* between point A and point B
* so that the len(AI) == len(AB)*F
* and I falls on AB segment.
*
* Example:
*
* F=0.5 : A----I----B
* F=1 : A---------B==I
* F=0 : A==I---------B
* F=.2 : A-I-------B
*/
void
interpolate_point4d(POINT4D *A, POINT4D *B, POINT4D *I, double F)
{
#if PARANOIA_LEVEL > 0
double absF=fabs(F);
if ( absF < 0 || absF > 1 )
{
lwerror("interpolate_point4d: invalid F (%g)", F);
}
#endif
I->x=A->x+((B->x-A->x)*F);
I->y=A->y+((B->y-A->y)*F);
I->z=A->z+((B->z-A->z)*F);
I->m=A->m+((B->m-A->m)*F);
}