path: root/libjava/java/awt/geom/Ellipse2D.java

/* Ellipse2D.java -- represents an ellipse in 2-D space
   Copyright (C) 2000, 2002, 2004 Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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GNU Classpath 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
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02111-1307 USA.

Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
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package java.awt.geom;


/**
 * Ellipse2D is the shape of an ellipse.
 * <BR>
 * <img src="doc-files/Ellipse-1.png" width="347" height="221"
 * alt="A drawing of an ellipse" /><BR>
 * The ellipse is defined by it's bounding box (shown in red),
 * and is defined by the implicit curve:<BR>
 * <blockquote>(<i>x</i>/<i>a</i>)<sup>2</sup> +
 * (<i>y</i>/<i>b</i>)<sup>2</sup> = 1<BR><BR></blockquote>
 *
 * @author Tom Tromey (tromey@cygnus.com)
 * @author Eric Blake (ebb9@email.byu.edu)
 *
 * @since 1.2
 */
public abstract class Ellipse2D extends RectangularShape
{
  /**
   * Ellipse2D is defined as abstract.
   * Implementing classes are Ellipse2D.Float and Ellipse2D.Double.
   */
  protected Ellipse2D()
  {
  }

  /**
   * Determines if a point is contained within the ellipse. <P>
   * @param x - x coordinate of the point.
   * @param y - y coordinate of the point.
   * @return true if the point is within the ellipse, false otherwise.
   */
  public boolean contains(double x, double y)
  {
    double rx = getWidth() / 2;
    double ry = getHeight() / 2;
    double tx = (x - (getX() + rx)) / rx;
    double ty = (y - (getY() + ry)) / ry;
    return tx * tx + ty * ty < 1.0;
  }

  /**
   * Determines if a rectangle is completely contained within the
   * ellipse. <P>
   * @param x - x coordinate of the upper-left corner of the rectangle
   * @param y - y coordinate of the upper-left corner of the rectangle
   * @param w - width of the rectangle
   * @param h - height of the rectangle
   * @return true if the rectangle is completely contained, false otherwise.
   */
  public boolean contains(double x, double y, double w, double h)
  {
    double x2 = x + w;
    double y2 = y + h;
    return (contains(x, y) && contains(x, y2) && contains(x2, y)
           && contains(x2, y2));
  }

  /**
   * Returns a PathIterator object corresponding to the ellipse.<P>
   *
   * Note: An ellipse cannot be represented exactly in PathIterator
   * segments, the outline is thefore approximated with cubic
   * Bezier segments.
   * 
   * @param at an optional transform.
   * @return A path iterator.
   */
  public PathIterator getPathIterator(AffineTransform at)
  {
    // An ellipse is just a complete arc.
    return new Arc2D.ArcIterator(this, at);
  }

  /**
   * Determines if a rectangle intersects any part of the ellipse.<P>
   * @param x - x coordinate of the upper-left corner of the rectangle
   * @param y - y coordinate of the upper-left corner of the rectangle
   * @param w - width of the rectangle
   * @param h - height of the rectangle
   * @return true if the rectangle intersects the ellipse, false otherwise.
   */
  public boolean intersects(double x, double y, double w, double h)
  {
    Rectangle2D r = new Rectangle2D.Double(x, y, w, h);
    if (! r.intersects(getX(), getY(), getWidth(), getHeight()))
      return false;

    if (contains(x, y) || contains(x, y + h) || contains(x + w, y)
        || contains(x + w, y + h))
      return true;

    Line2D l1 = new Line2D.Double(getX(), getY() + (getHeight() / 2),
                                  getX() + getWidth(),
                                  getY() + (getHeight() / 2));
    Line2D l2 = new Line2D.Double(getX() + (getWidth() / 2), getY(),
                                  getX() + (getWidth() / 2),
                                  getY() + getHeight());

    if (l1.intersects(r) || l2.intersects(r))
      return true;

    return false;
  }

  /**
   * An {@link Ellipse2D} that stores its coordinates using <code>double</code>
   * primitives.
   */
  public static class Double extends Ellipse2D
  {
    /**
     * The height of the ellipse.
     */
    public double height;

    /**
     * The width of the ellipse.
     */
    public double width;

    /**
     * The upper-left x coordinate of the bounding-box
     */
    public double x;

    /**
     * The upper-left y coordinate of the bounding-box
     */
    public double y;

    /**
     * Creates a new Ellipse2D with an upper-left coordinate of (0,0)
     * and a zero size.
     */
    public Double()
    {
    }

    /**
     * Creates a new Ellipse2D within a given rectangle
     * using double-precision coordinates.<P>
     * @param x - x coordinate of the upper-left of the bounding rectangle
     * @param y - y coordinate of the upper-left of the bounding rectangle
     * @param w - width of the ellipse
     * @param h - height of the ellipse
     */
    public Double(double x, double y, double w, double h)
    {
      this.x = x;
      this.y = y;
      height = h;
      width = w;
    }

    /**
     * Returns the bounding-box of the ellipse.
     * @return The bounding box.
     */
    public Rectangle2D getBounds2D()
    {
      return new Rectangle2D.Double(x, y, width, height);
    }

    /**
     * Returns the height of the ellipse.
     * @return The height of the ellipse.
     */
    public double getHeight()
    {
      return height;
    }

    /**
     * Returns the width of the ellipse.
     * @return The width of the ellipse.
     */
    public double getWidth()
    {
      return width;
    }

    /**
     * Returns x coordinate of the upper-left corner of
     * the ellipse's bounding-box.
     * @return The x coordinate.
     */
    public double getX()
    {
      return x;
    }

    /**
     * Returns y coordinate of the upper-left corner of
     * the ellipse's bounding-box.
     * @return The y coordinate.
     */
    public double getY()
    {
      return y;
    }

    /**
     * Returns <code>true</code> if the ellipse encloses no area, and
     * <code>false</code> otherwise.
     * 
     * @return A boolean.
     */
    public boolean isEmpty()
    {
      return height <= 0 || width <= 0;
    }

    /**
     * Sets the geometry of the ellipse's bounding box.<P>
     *
     * @param x - x coordinate of the upper-left of the bounding rectangle
     * @param y - y coordinate of the upper-left of the bounding rectangle
     * @param w - width of the ellipse
     * @param h - height of the ellipse
     */
    public void setFrame(double x, double y, double w, double h)
    {
      this.x = x;
      this.y = y;
      height = h;
      width = w;
    }
  } // class Double

  /**
   * An {@link Ellipse2D} that stores its coordinates using <code>float</code>
   * primitives.
   */
  public static class Float extends Ellipse2D
  {
    /**
     * The height of the ellipse.
     */
    public float height;

    /**
     * The width of the ellipse.
     */
    public float width;

    /**
     * The upper-left x coordinate of the bounding-box
     */
    public float x;

    /**
     * The upper-left y coordinate of the bounding-box
     */
    public float y;

    /**
     * Creates a new Ellipse2D with an upper-left coordinate of (0,0)
     * and a zero size.
     */
    public Float()
    {
    }

    /**
     * Creates a new Ellipse2D within a given rectangle
     * using floating-point precision.<P>
     * @param x - x coordinate of the upper-left of the bounding rectangle
     * @param y - y coordinate of the upper-left of the bounding rectangle
     * @param w - width of the ellipse
     * @param h - height of the ellipse
     *
     */
    public Float(float x, float y, float w, float h)
    {
      this.x = x;
      this.y = y;
      this.height = h;
      this.width = w;
    }

    /**
     * Returns the bounding-box of the ellipse.
     * @return The bounding box.
     */
    public Rectangle2D getBounds2D()
    {
      return new Rectangle2D.Float(x, y, width, height);
    }

    /**
     * Returns the height of the ellipse.
     * @return The height of the ellipse.
     */
    public double getHeight()
    {
      return height;
    }

    /**
     * Returns the width of the ellipse.
     * @return The width of the ellipse.
     */
    public double getWidth()
    {
      return width;
    }

    /**
     * Returns x coordinate of the upper-left corner of
     * the ellipse's bounding-box.
     * @return The x coordinate.
     */
    public double getX()
    {
      return x;
    }

    /**
     * Returns y coordinate of the upper-left corner of
     * the ellipse's bounding-box.
     * @return The y coordinate.
     */
    public double getY()
    {
      return y;
    }

    /**
     * Returns <code>true</code> if the ellipse encloses no area, and
     * <code>false</code> otherwise.
     * 
     * @return A boolean.
     */
    public boolean isEmpty()
    {
      return height <= 0 || width <= 0;
    }

    /**
     * Sets the geometry of the ellipse's bounding box.<P>
     *
     * @param x - x coordinate of the upper-left of the bounding rectangle
     * @param y - y coordinate of the upper-left of the bounding rectangle
     * @param w - width of the ellipse
     * @param h - height of the ellipse
     */
    public void setFrame(float x, float y, float w, float h)
    {
      this.x = x;
      this.y = y;
      height = h;
      width = w;
    }

    /**
     * Sets the geometry of the ellipse's bounding box.
     *
     * Note: This leads to a loss of precision.<P>
     *
     * @param x - x coordinate of the upper-left of the bounding rectangle
     * @param y - y coordinate of the upper-left of the bounding rectangle
     * @param w - width of the ellipse
     * @param h - height of the ellipse
     */
    public void setFrame(double x, double y, double w, double h)
    {
      this.x = (float) x;
      this.y = (float) y;
      height = (float) h;
      width = (float) w;
    }
  } // class Float
} // class Ellipse2D