line_2d.h

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// -*-c++-*-
 
/*
 *Copyright:
 
 Copyright (C) Hidehisa Akiyama
 
 This code 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 3 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 *EndCopyright:
 */
 
 
#ifndef RCSC_GEOM_LINE2D_H
#define RCSC_GEOM_LINE2D_H
 
#include <rcsc/geom/vector_2d.h>
 
#include <cmath>
 
namespace rcsc {
 
class Line2D {
public:
 
    static const double EPSILON; 
    static const double ERROR_VALUE; 
 
private:
 
    double M_a; 
    double M_b; 
    double M_c; 
 
    // never used
    Line2D();
 
public:
    Line2D( const double a,
            const double b,
            const double c )
        : M_a( a ),
          M_b( b ),
          M_c( c )
      { }
 
    Line2D( const Vector2D & p1,
            const Vector2D & p2 )
      {
          assign( p1, p2 );
      }
 
    Line2D( const Vector2D & origin,
            const AngleDeg & linedir )
      {
          assign( origin, linedir );
      }
 
    const Line2D & assign( const Vector2D & p1,
                           const Vector2D & p2 )
      {
          M_a = -( p2.y - p1.y );
          M_b = p2.x - p1.x;
          M_c = -M_a * p1.x - M_b * p1.y;
          return *this;
      }
 
    const Line2D & assign( const Vector2D & origin,
                           const AngleDeg & linedir )
      {
          M_a = - linedir.sin();
          M_b = linedir.cos();
          M_c = -M_a * origin.x - M_b * origin.y;
          return *this;
      }
 
    double a() const
      {
          return M_a;
      }
 
    double b() const
      {
          return M_b;
      }
 
    double c() const
      {
          return M_c;
      }
 
    double getX( const double y ) const
      {
          if ( std::fabs( M_a ) < EPSILON )
          {
              return ERROR_VALUE;
          }
          return -( M_b * y + M_c ) / M_a;
      }
 
    double getY( const double x ) const
      {
          if ( std::fabs( M_b ) < EPSILON )
          {
              return ERROR_VALUE;
          }
 
          return -( M_a * x + M_c ) / M_b;
      }
 
    double dist( const Vector2D & p ) const
      {
          return std::fabs( ( M_a * p.x + M_b * p.y + M_c )
                            / std::sqrt( M_a * M_a + M_b * M_b ) );
      }
    double dist2( const Vector2D & p ) const
      {
          double d = M_a * p.x + M_b * p.y + M_c;
          return (d * d) / (M_a * M_a + M_b * M_b);
      }
 
    bool isParallel( const Line2D & line ) const
      {
          return std::fabs( a() * line.b() - line.a() * b() ) < EPSILON;
      }
 
    Vector2D intersection( const Line2D & line ) const
      {
          return intersection( *this, line );
      }
 
    Line2D perpendicular( const Vector2D & p ) const
      {
          return Line2D( b(), -a(), a() * p.y - b() * p.x );
      }
 
    Vector2D projection( const Vector2D & p ) const
      {
          return intersection( perpendicular( p ) );
      }
 
    // static utility
 
    static
    Vector2D intersection( const Line2D & line1,
                           const Line2D & line2 );
 
    static
    Line2D angle_bisector( const Vector2D & origin,
                           const AngleDeg & left,
                           const AngleDeg & right )
      {
          return Line2D( origin, AngleDeg::bisect( left, right ) );
      }
 
    static
    Line2D perpendicular_bisector( const Vector2D & p1,
                                   const Vector2D & p2 );
 
};
 
}
 
#endif