lwpoly_covers_point2d()

int lwpoly_covers_point2d	(	const LWPOLY *	poly,
		const POINT2D *	pt_to_test
	)

Given a polygon (lon/lat decimal degrees) and point (lon/lat decimal degrees) and a guaranteed outside point (lon/lat decimal degrees) (calculate with gbox_pt_outside()) return LW_TRUE if point is inside or on edge of polygon.

Definition at line 2521 of file lwgeodetic.c.

{
        uint32_t i;
        int in_hole_count = 0;
        POINT3D p;
        GEOGRAPHIC_POINT gpt_to_test;
        POINT2D pt_outside;
        GBOX gbox;
#if POSTGIS_DEBUG_LEVEL >= 4
        char *geom_ewkt;
#endif
        gbox.flags = 0;
 
        /* Nulls and empties don't contain anything! */
        if ( ! poly || lwgeom_is_empty((LWGEOM*)poly) )
        {
                LWDEBUG(4,"returning false, geometry is empty or null");
                return LW_FALSE;
        }
 
        /* Make sure we have boxes */
        if ( poly->bbox )
                gbox = *(poly->bbox);
        else
                lwgeom_calculate_gbox_geodetic((LWGEOM*)poly, &gbox);
 
        /* Point not in box? Done! */
        geographic_point_init(pt_to_test->x, pt_to_test->y, &gpt_to_test);
        geog2cart(&gpt_to_test, &p);
        if ( ! gbox_contains_point3d(&gbox, &p) )
        {
                LWDEBUG(4, "the point is not in the box!");
                return LW_FALSE;
        }
 
        /* Calculate our outside point from the gbox */
        lwpoly_pt_outside(poly, &pt_outside);
 
        LWDEBUGF(4, "pt_outside POINT(%.18g %.18g)", pt_outside.x, pt_outside.y);
        LWDEBUGF(4, "pt_to_test POINT(%.18g %.18g)", pt_to_test->x, pt_to_test->y);
#if POSTGIS_DEBUG_LEVEL >= 4
        geom_ewkt = lwgeom_to_ewkt((LWGEOM*)poly);
        LWDEBUGF(4, "polygon %s", geom_ewkt);
        lwfree(geom_ewkt);
        geom_ewkt = gbox_to_string(&gbox);
        LWDEBUGF(4, "gbox %s", geom_ewkt);
        lwfree(geom_ewkt);
#endif
 
        /* Not in outer ring? We're done! */
        if ( ! ptarray_contains_point_sphere(poly->rings[0], &pt_outside, pt_to_test) )
        {
                LWDEBUG(4,"returning false, point is outside ring");
                return LW_FALSE;
        }
 
        LWDEBUGF(4, "testing %d rings", poly->nrings);
 
        /* But maybe point is in a hole... */
        for ( i = 1; i < poly->nrings; i++ )
        {
                LWDEBUGF(4, "ring test loop %d", i);
                /* Count up hole containment. Odd => outside boundary. */
                if ( ptarray_contains_point_sphere(poly->rings[i], &pt_outside, pt_to_test) )
                        in_hole_count++;
        }
 
        LWDEBUGF(4, "in_hole_count == %d", in_hole_count);
 
        if ( in_hole_count % 2 )
        {
                LWDEBUG(4,"returning false, inner ring containment count is odd");
                return LW_FALSE;
        }
 
        LWDEBUG(4,"returning true, inner ring containment count is even");
        return LW_TRUE;
}

References LWPOLY::bbox, GBOX::flags, gbox_contains_point3d(), gbox_to_string(), geog2cart(), geographic_point_init(), LW_FALSE, LW_TRUE, LWDEBUG, LWDEBUGF, lwfree(), lwgeom_calculate_gbox_geodetic(), lwgeom_is_empty(), lwgeom_to_ewkt(), lwpoly_pt_outside(), LWPOLY::nrings, ptarray_contains_point_sphere(), LWPOLY::rings, POINT2D::x, and POINT2D::y.

Referenced by lwgeom_covers_lwgeom_sphere(), lwgeom_distance_spheroid(), lwpoly_covers_pointarray(), test_lwpoly_covers_point2d(), and test_tree_circ_pip2().

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