001 package edu.nrao.sss.geom;
002
003 import java.awt.Rectangle;
004 import java.awt.Shape;
005 import java.awt.geom.AffineTransform;
006 import java.awt.geom.Ellipse2D;
007 import java.awt.geom.PathIterator;
008 import java.awt.geom.Point2D;
009 import java.awt.geom.Rectangle2D;
010
011 /**
012 * A circle described by a central point and radial length.
013 * This circle class fits in with java's {@link java.awt.geom 2D} package.
014 * <p>
015 * <b>Version Info:</b>
016 * <table style="margin-left:2em">
017 * <tr><td>$Revision: 797 $</td></tr>
018 * <tr><td>$Date: 2007-08-08 16:48:50 -0600 (Wed, 08 Aug 2007) $</td></tr>
019 * <tr><td>$Author: dharland $ (last person to modify)</td></tr>
020 * </table></p>
021 *
022 * @author David M. Harland
023 * @since 2007-08-07
024 */
025 public class Circle
026 implements Shape, Cloneable
027 {
028 private Point2D center;
029 private double radius;
030 private Ellipse2D ellipse;
031
032 /**
033 * Creates a new circle, centered at the origin, with the given radius.
034 *
035 * @param radius the radius of this circle. The units are arbitrary,
036 * but are often taken to be pixels.
037 */
038 public Circle(double radius)
039 {
040 this(new Point2D.Double(), radius);
041 }
042
043 /**
044 * Creates a new circle with the given center and radius.
045 *
046 * @param center the center of this circle.
047 *
048 * @param radius the radius of this circle. The units are arbitrary,
049 * but are often taken to be pixels. If this value
050 * is infinite, negative, or not a number, the radius
051 * will be set to one.
052 */
053 public Circle(Point2D center, double radius)
054 {
055 this.center = (center == null) ? new Point2D.Double()
056 : (Point2D)center.clone();
057
058 this.radius = radiusIsValid(radius) ? radius : 1.0;
059
060 ellipse = new Ellipse2D.Double();
061
062 updateEllipse();
063 }
064
065 /** Updates the ellipse delegate to match this circle. */
066 private void updateEllipse()
067 {
068 double diameter = 2.0 * radius;
069
070 ellipse.setFrame(center.getX() - radius,
071 center.getY() - radius, diameter, diameter);
072 }
073
074 //============================================================================
075 //
076 //============================================================================
077
078 /** Returns <i>true</i> if newRadius is non-negative and finite. */
079 private boolean radiusIsValid(double newRadius)
080 {
081 return (newRadius >= 0.0) && !Double.isInfinite(newRadius)
082 && !Double.isNaN(newRadius);
083 }
084
085 /**
086 * Sets the radius of this circle.
087 * If {@code newRadius} is negative, infinite, or not a number, an
088 * <tt>IllegalArgumentException</tt> is thrown.
089 *
090 * @param newRadius the new radius of this circle.
091 */
092 public void setRadius(double newRadius)
093 {
094 if (radiusIsValid(newRadius))
095 {
096 radius = newRadius;
097 }
098 else
099 {
100 throw new IllegalArgumentException(
101 "Tried to set radius to " + newRadius +
102 ". Radius must be a finite non-negative number.");
103 }
104 }
105
106 /**
107 * Returns the radius of this circle.
108 * The units are arbitrary, but are often taken to be pixels.
109 * @return the radius of this circle.
110 */
111 public double getRadius() { return radius; }
112
113 /**
114 * Returns the diameter of this circle.
115 * The units are arbitrary, but are often taken to be pixels.
116 * @return the diameter of this circle.
117 */
118 public double getDiameter() { return 2.0 * radius; }
119
120 /**
121 * Sets the center of this circle to be coincident with {@code newCenter}.
122 * Note that this circle will <i>not</i> hold a reference to
123 * {@code newCenter}, so changes made to it after calling this method
124 * will not be reflected herein.
125 * <p>
126 * If {@code newCenter} is <i>null</i>, the center of this circle will
127 * not be altered.</p>
128 *
129 * @param newCenter the new center of this circle.
130 */
131 public void setCenter(Point2D newCenter)
132 {
133 if (newCenter != null)
134 center.setLocation(newCenter.getX(), newCenter.getY());
135 }
136
137 /**
138 * Returns a copy of the center of this circle.
139 * @return a copy of the center of this circle.
140 */
141 public Point2D getCenter()
142 {
143 return (Point2D)center.clone();
144 }
145
146 //============================================================================
147 // IMPLEMENTATION OF Shape INTERFACE
148 //============================================================================
149
150 public boolean contains(double x, double y)
151 {
152 return ellipse.contains(x, y);
153 }
154
155 public boolean contains(double x, double y, double w, double h)
156 {
157 return ellipse.contains(x, y, w, h);
158 }
159
160 public boolean contains(Point2D p)
161 {
162 return ellipse.contains(p);
163 }
164
165 public boolean contains(Rectangle2D r)
166 {
167 return ellipse.contains(r);
168 }
169
170 public Rectangle getBounds()
171 {
172 return ellipse.getBounds();
173 }
174
175 public Rectangle2D getBounds2D()
176 {
177 return ellipse.getBounds2D();
178 }
179
180 public PathIterator getPathIterator(AffineTransform at)
181 {
182 return ellipse.getPathIterator(at);
183 }
184
185 public PathIterator getPathIterator(AffineTransform at, double flatness)
186 {
187 return ellipse.getPathIterator(at, flatness);
188 }
189
190 public boolean intersects(double x, double y, double w, double h)
191 {
192 return ellipse.intersects(x, y, w, h);
193 }
194
195 /** {@inheritDoc} */
196 public boolean intersects(Rectangle2D r)
197 {
198 return ellipse.intersects(r);
199 }
200
201 //============================================================================
202 //
203 //============================================================================
204
205 /**
206 * Creates a copy of this circle.
207 * If anything goes wrong during the cloning process
208 * a runtime exception is thrown.
209 */
210 @Override
211 public Circle clone()
212 {
213 Circle clone = null;
214
215 try
216 {
217 clone = (Circle)super.clone();
218
219 clone.center = (Point2D)this.center.clone();
220
221 clone.ellipse = (Ellipse2D)this.ellipse.clone();
222 }
223 catch (CloneNotSupportedException ex)
224 {
225 throw new RuntimeException(ex);
226 }
227
228 return clone;
229 }
230 }