agg-2.5/include/agg_shorten_path.h

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//----------------------------------------------------------------------------
// Anti-Grain Geometry (AGG) - Version 2.5
// A high quality rendering engine for C++
// Copyright (C) 2002-2006 Maxim Shemanarev
// Contact: mcseem@antigrain.com
//          mcseemagg@yahoo.com
//          http://antigrain.com
// 
// AGG is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
// 
// AGG is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with AGG; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, 
// MA 02110-1301, USA.
//----------------------------------------------------------------------------

#ifndef AGG_SHORTEN_PATH_INCLUDED
#define AGG_SHORTEN_PATH_INCLUDED

#include "agg_basics.h"
#include "agg_vertex_sequence.h"

namespace agg
{

    //===========================================================shorten_path
    template<class VertexSequence> 
    void shorten_path(VertexSequence& vs, double s, unsigned closed = 0)
    {
        typedef typename VertexSequence::value_type vertex_type;

        if(s > 0.0 && vs.size() > 1)
        {
            double d;
            int n = int(vs.size() - 2);
            while(n)
            {
                d = vs[n].dist;
                if(d > s) break;
                vs.remove_last();
                s -= d;
                --n;
            }
            if(vs.size() < 2)
            {
                vs.remove_all();
            }
            else
            {
                n = vs.size() - 1;
                vertex_type& prev = vs[n-1];
                vertex_type& last = vs[n];
                d = (prev.dist - s) / prev.dist;
                double x = prev.x + (last.x - prev.x) * d;
                double y = prev.y + (last.y - prev.y) * d;
                last.x = x;
                last.y = y;
                if(!prev(last)) vs.remove_last();
                vs.close(closed != 0);
            }
        }
    }


}

#endif