mapnik/include/mapnik/geom_util.hpp

/*****************************************************************************
 * 
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2011 Artem Pavlenko
 *
 * 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.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

#ifndef MAPNIK_GEOM_UTIL_HPP
#define MAPNIK_GEOM_UTIL_HPP

// mapnik
#include <mapnik/box2d.hpp>
#include <mapnik/vertex.hpp>

// boost
#include <boost/tuple/tuple.hpp>

// stl
#include <cmath>

namespace mapnik
{
template <typename T>
bool clip_test(T p,T q,double& tmin,double& tmax)
{
    double r;
    bool result=true;
    if (p<0.0)
    {
        r=q/p;
        if (r>tmax) result=false;
        else if (r>tmin) tmin=r;
    }
    else if (p>0.0)
    {
        r=q/p;
        if (r<tmin) result=false;
        else if (r<tmax) tmax=r;
    } else if (q<0.0) result=false;
    return result;
}
    
template <typename T,typename Image>
bool clip_line(T& x0,T& y0,T& x1,T& y1,box2d<T> const& box)
{
    double tmin=0.0;
    double tmax=1.0;
    double dx=x1-x0;
    if (clip_test<double>(-dx,x0,tmin,tmax))
    {
        if (clip_test<double>(dx,box.width()-x0,tmin,tmax))
        {
            double dy=y1-y0;
            if (clip_test<double>(-dy,y0,tmin,tmax))
            {
                if (clip_test<double>(dy,box.height()-y0,tmin,tmax))
                {
                    if (tmax<1.0)
                    {
                        x1=static_cast<T>(x0+tmax*dx);
                        y1=static_cast<T>(y0+tmax*dy);
                    }
                    if (tmin>0.0)
                    {
                        x0+=static_cast<T>(tmin*dx);
                        y0+=static_cast<T>(tmin*dy);
                    }
                    return true;
                }
            }
        }
    }
    return false;
}
    
template <typename Iter> 
inline bool point_inside_path(double x,double y,Iter start,Iter end)
{
    bool inside=false;
    double x0=boost::get<0>(*start);
    double y0=boost::get<1>(*start);
        
    double x1,y1;
    while (++start!=end) 
    {
        if ( boost::get<2>(*start) == SEG_MOVETO)
        {
            x0 = boost::get<0>(*start);
            y0 = boost::get<1>(*start);
            continue;
        }               
        x1=boost::get<0>(*start);
        y1=boost::get<1>(*start);
            
        if ((((y1 <= y) && (y < y0)) ||
             ((y0 <= y) && (y < y1))) &&
            ( x < (x0 - x1) * (y - y1)/ (y0 - y1) + x1))
            inside=!inside;
        x0=x1;
        y0=y1;
    }
    return inside;
}

inline bool point_in_circle(double x,double y,double cx,double cy,double r)
{
    double dx = x - cx;
    double dy = y - cy;
    double d2 = dx * dx + dy * dy;
    return (d2 <= r * r);
}
    
template <typename T>
inline T sqr(T x)
{
    return x * x;
}

inline double distance2(double x0,double y0,double x1,double y1)
{
    double dx = x1 - x0;
    double dy = y1 - y0;
    return sqr(dx) + sqr(dy);
}
    
inline double distance(double x0,double y0, double x1,double y1)
{
    return std::sqrt(distance2(x0,y0,x1,y1));
}
    
inline double point_to_segment_distance(double x, double y, 
                                        double ax, double ay, 
                                        double bx, double by)
{
    double len2 = distance2(ax,ay,bx,by);
        
    if (len2 < 1e-14) 
    {
        return distance(x,y,ax,ay);
    }
        
    double r = ((x - ax)*(bx - ax) + (y - ay)*(by -ay))/len2;
    if ( r < 0 )
    {
        return distance(x,y,ax,ay);
    }
    else if (r > 1)
    {
        return distance(x,y,bx,by);
    }
    double s = ((ay - y)*(bx - ax) - (ax - x)*(by - ay))/len2;
    return std::fabs(s) * std::sqrt(len2);
}
        
template <typename Iter> 
inline bool point_on_path(double x,double y,Iter start,Iter end, double tol)
{
    double x0=boost::get<0>(*start);
    double y0=boost::get<1>(*start);
    double x1,y1;
    while (++start != end) 
    {
        if ( boost::get<2>(*start) == SEG_MOVETO)
        {
            x0 = boost::get<0>(*start);
            y0 = boost::get<1>(*start);
            continue;
        }               
        x1=boost::get<0>(*start);
        y1=boost::get<1>(*start);
            
        double distance = point_to_segment_distance(x,y,x0,y0,x1,y1);
        if (distance < tol)
            return true;
        x0=x1;
        y0=y1;
    }
    return false;
}
    
// filters
struct filter_in_box
{
    box2d<double> box_;
    explicit filter_in_box(const box2d<double>& box)
        : box_(box) {}

    bool pass(const box2d<double>& extent) const
    {
        return extent.intersects(box_);
    }
};

struct filter_at_point
{
    coord2d pt_;
    explicit filter_at_point(const coord2d& pt)
        : pt_(pt) {}
    bool pass(const box2d<double>& extent) const
    {
        return extent.contains(pt_);
    }
};
}

#endif // MAPNIK_GEOM_UTIL_HPP