ptarray_contains_point_partial()

int ptarray_contains_point_partial	(	const POINTARRAY *	pa,
		const POINT2D *	pt,
		int	check_closed,
		int *	winding_number
	)

Definition at line 746 of file ptarray.c.

{
        int wn = 0;
        uint32_t i;
        double side;
        const POINT2D *seg1;
        const POINT2D *seg2;
        double ymin, ymax;
 
        seg1 = getPoint2d_cp(pa, 0);
        seg2 = getPoint2d_cp(pa, pa->npoints-1);
        if ( check_closed && ! p2d_same(seg1, seg2) )
                lwerror("ptarray_contains_point called on unclosed ring");
 
        for ( i=1; i < pa->npoints; i++ )
        {
                seg2 = getPoint2d_cp(pa, i);
 
                /* Zero length segments are ignored. */
                if ( seg1->x == seg2->x && seg1->y == seg2->y )
                {
                        seg1 = seg2;
                        continue;
                }
 
                ymin = FP_MIN(seg1->y, seg2->y);
                ymax = FP_MAX(seg1->y, seg2->y);
 
                /* Only test segments in our vertical range */
                if ( pt->y > ymax || pt->y < ymin )
                {
                        seg1 = seg2;
                        continue;
                }
 
                side = lw_segment_side(seg1, seg2, pt);
 
                /*
                * A point on the boundary of a ring is not contained.
                * WAS: if (fabs(side) < 1e-12), see #852
                */
                if ( (side == 0) && lw_pt_in_seg(pt, seg1, seg2) )
                {
                        return LW_BOUNDARY;
                }
 
                /*
                * If the point is to the left of the line, and it's rising,
                * then the line is to the right of the point and
                * circling counter-clockwise, so increment.
                */
                if ( (side < 0) && (seg1->y <= pt->y) && (pt->y < seg2->y) )
                {
                        wn++;
                }
 
                /*
                * If the point is to the right of the line, and it's falling,
                * then the line is to the right of the point and circling
                * clockwise, so decrement.
                */
                else if ( (side > 0) && (seg2->y <= pt->y) && (pt->y < seg1->y) )
                {
                        wn--;
                }
 
                seg1 = seg2;
        }
 
        /* Sent out the winding number for calls that are building on this as a primitive */
        if ( winding_number )
                *winding_number = wn;
 
        /* Outside */
        if (wn == 0)
        {
                return LW_OUTSIDE;
        }
 
        /* Inside */
        return LW_INSIDE;
}

References FP_MAX, FP_MIN, getPoint2d_cp(), LW_BOUNDARY, LW_INSIDE, LW_OUTSIDE, lw_pt_in_seg(), lw_segment_side(), lwerror(), POINTARRAY::npoints, p2d_same(), POINT2D::x, and POINT2D::y.

Referenced by _lwt_AddPoint(), _lwt_CheckEdgeCrossing(), lwcompound_contains_point(), lwt_ChangeEdgeGeom(), and ptarray_contains_point().

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