graphiq/library/geometric/ellipse.cpp

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   4 /*****************************************************************************\
   5 *                                                                             *
   6 *  Name   : ellipse                                                           *
   7 *  Author : Chris Koeritz                                                     *
   8 *                                                                             *
   9 *******************************************************************************
  10 * Copyright (c) 1992-$now By Author.  This program is free software; you can  *
  11 * redistribute it and/or modify it under the terms of the GNU General Public  *
  12 * License as published by the Free Software Foundation; either version 2 of   *
  13 * the License or (at your option) any later version.  This is online at:      *
  14 *     http://www.fsf.org/copyleft/gpl.html                                    *
  15 * Please send any updates to: fred@gruntose.com                               *
  16 \*****************************************************************************/
  17
  18 #include "cartesian_objects.h"
  19 #include "ellipse.h"
  20 #include "line.h"
  21 #include "rectangle.h"
  22
  23 #include <basis/functions.h>
  24
  25 #include <math.h>
  26
  27 using namespace basis;
  28
  29 namespace geometric {
  30
  31 ellipse::ellipse()
  32 : _center(cartesian_point::origin()),
  33   _width_from_center(1),
  34   _height_from_center(1)
  35 {}
  36
  37 ellipse::ellipse(const cartesian_point &a_center, double a_width_from_center,
  38     double a_height_from_center)
  39 : _center(a_center),
  40   _width_from_center(a_width_from_center),
  41   _height_from_center(a_height_from_center)
  42 {}
  43
  44 ellipse::ellipse(const ellipse &to_copy)
  45 : _center(),
  46   _width_from_center(0),
  47   _height_from_center(0)
  48 { *this = to_copy; }
  49
  50 ellipse::~ellipse() {}
  51
  52 ellipse &ellipse::operator = (const ellipse &to_copy)
  53 {
  54   if (this == &to_copy) return *this;
  55   _center = to_copy._center;
  56   _width_from_center = to_copy._width_from_center;
  57   _height_from_center = to_copy._height_from_center;
  58   return *this;
  59 }
  60
  61 double ellipse::area() const
  62 { return absolute_value(PI_APPROX * _width_from_center * _height_from_center); }
  63
  64 double ellipse::perimeter() const
  65 {
  66   double w = _width_from_center;
  67   double h = _height_from_center;
  68   double perim_temp = sqrt(square(h) + square(w)) / 2;
  69   return 2.0 * PI_APPROX * perim_temp;
  70 }
  71
  72 cartesian_point ellipse::location(const double_angle &where) const
  73 {
  74   double a = _width_from_center;
  75   double b = _height_from_center;
  76   double a_multiplier = square(where.tangent());
  77   double denom = sqrt(square(b) + square(a) * a_multiplier);
  78   double ab = a * b;
  79   double tango = where.tangent();
  80   cartesian_point to_return(ab / denom, ab * tango / denom);
  81
  82   // the following negates the x component if the angle is in the appropriate
  83   // part of the ellipse.
  84   int ang = int(where.get(DEGREES));
  85   double adjustment = where.get(DEGREES) - double(ang);
  86   ang %= 360;
  87   double adjusted_ang = ang + adjustment;
  88   if ( (adjusted_ang < 270.0) && (adjusted_ang > 90.0) )
  89      to_return.set(to_return.x() * -1.0, to_return.y());
  90   to_return += _center;
  91   return to_return;
  92 }
  93
  94 bool ellipse::inside(const cartesian_point &where) const
  95 {
  96   double dist = where.distance(_center);
  97   double_angle to_point = double_angle(asin(where.y() / dist), RADIANS);
  98   cartesian_point intersector = location(to_point);
  99   return dist <= intersector.distance(_center)? true : false;
 100 }
 101
 102 cartesian_point ellipse::center() const { return _center; }
 103
 104 double ellipse::width_from_center() const { return _width_from_center; }
 105
 106 double ellipse::height_from_center() const { return _height_from_center; }
 107
 108 void ellipse::center(const cartesian_point &to_set) { _center = to_set; }
 109
 110 void ellipse::width_from_center(double to_set)
 111 { _width_from_center = to_set; }
 112
 113 void ellipse::height_from_center(double to_set)
 114 { _height_from_center = to_set; }
 115
 116 } // namespace.
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