geography_centroid_from_mline()

LWPOINT * geography_centroid_from_mline	(	const LWMLINE *	mline,
		SPHEROID *	s
	)

Split lines into segments and calculate with middle of segment as weighted point.

Definition at line 251 of file geography_centroid.c.

{
    double_t tolerance = 0.0;
    uint32_t size = 0;
    uint32_t i, k, j = 0;
    POINT3DM* points;
    LWPOINT* result;
 
    /* get total number of points */
    for (i = 0; i < mline->ngeoms; i++) {
        size += (mline->geoms[i]->points->npoints - 1) * 2;
    }
 
    points = palloc(size*sizeof(POINT3DM));
 
    for (i = 0; i < mline->ngeoms; i++) {
        LWLINE* line = mline->geoms[i];
 
        /* add both points of line segment as weighted point */
        for (k = 0; k < line->points->npoints - 1; k++) {
            const POINT2D* p1 = getPoint2d_cp(line->points, k);
            const POINT2D* p2 = getPoint2d_cp(line->points, k+1);
            double_t weight;
 
            /* use line-segment length as weight */
            LWPOINT* lwp1 = lwpoint_make2d(mline->srid, p1->x, p1->y);
            LWPOINT* lwp2 = lwpoint_make2d(mline->srid, p2->x, p2->y);
            LWGEOM* lwgeom1 = lwpoint_as_lwgeom(lwp1);
            LWGEOM* lwgeom2 = lwpoint_as_lwgeom(lwp2);
            lwgeom_set_geodetic(lwgeom1, LW_TRUE);
            lwgeom_set_geodetic(lwgeom2, LW_TRUE);
 
            /* use point distance as weight */
            weight = lwgeom_distance_spheroid(lwgeom1, lwgeom2, s, tolerance);
 
            points[j].x = p1->x;
            points[j].y = p1->y;
            points[j].m = weight;
            j++;
 
            points[j].x = p2->x;
            points[j].y = p2->y;
            points[j].m = weight;
            j++;
 
            lwgeom_free(lwgeom1);
            lwgeom_free(lwgeom2);
        }
    }
 
    result = geography_centroid_from_wpoints(mline->srid, points, size);
    pfree(points);
    return result;
}

References geography_centroid_from_wpoints(), LWMLINE::geoms, getPoint2d_cp(), LW_TRUE, lwgeom_distance_spheroid(), lwgeom_free(), lwgeom_set_geodetic(), lwpoint_as_lwgeom(), lwpoint_make2d(), POINT3DM::m, LWMLINE::ngeoms, POINTARRAY::npoints, LWLINE::points, s, LWMLINE::srid, POINT2D::x, POINT3DM::x, POINT2D::y, and POINT3DM::y.

Referenced by geography_centroid().

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