cae-tools/poly2d/p2d_offset.cpp

/*
 * p2d_offset.cpp - Simple offsetting (without dogbones)
 *
 * Written 2012 by Werner Almesberger
 * Copyright 2012 by Werner Almesberger
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 */

/*
 * References:
 * http://www.cgal.org/Manual/latest/examples/Straight_skeleton_2/
 *   Create_saop_from_polygon_with_holes_2.cpp
 * http://www.cgal.org/Manual/latest/examples/Straight_skeleton_2/print.h
 */

extern "C" {
	#include <assert.h>

	#include "poly2d.h"
}

#include "cgal_helper.h"

#include <vector>
#include <boost/shared_ptr.hpp>

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Polygon_with_holes_2.h>
#include <CGAL/create_offset_polygons_from_polygon_with_holes_2.h>


typedef CGAL::Exact_predicates_inexact_constructions_kernel K;

typedef CGAL::Polygon_2<K> Polygon_2;
typedef CGAL::Polygon_with_holes_2<K> Polygon_with_holes;

typedef boost::shared_ptr<Polygon_2> PolygonPtr;

typedef std::vector<PolygonPtr> PolygonPtrVector;


extern "C" struct p2d *p2d_offset_holes(const struct p2d *p,
    const struct p2d *holes, double off)
{
	const struct p2d *h;
	struct p2d *res = NULL, **last = &res;

	assert(p2d_is_closed(p));
	Polygon_with_holes poly(p2d_to_P2(p, 1));

	for (h = holes; h; h = h->next) {
		assert(p2d_is_closed(h));
		poly.add_hole(p2d_to_P2(h, 0));
	}

	PolygonPtrVector tmp = off > 0 ?
	     CGAL::create_exterior_skeleton_and_offset_polygons_2(off,
	        poly.outer_boundary()) :
	    CGAL::create_interior_skeleton_and_offset_polygons_2(-off, poly);

	for (PolygonPtrVector::const_iterator pit = tmp.begin();
	    pit != tmp.end(); ++pit) {
		*last = P2_to_p2d(**pit);
		last = &(*last)->next;
	}

	return res;
}


extern "C" struct p2d *p2d_offset(const struct p2d *p, double off)
{
	return p2d_offset_holes(p, NULL, off);
}