ellipse2d.java

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/*
 * @(#)Ellipse2D.java	1.15 03/01/23
 *
 * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.awt.geom;

/**
 * The <code>Ellipse2D</code> class describes an ellipse that is defined
 * by a bounding rectangle.
 * <p>
 * This class is only the abstract superclass for all objects which
 * store a 2D ellipse.
 * The actual storage representation of the coordinates is left to
 * the subclass.
 *
 * @version 1.15, 01/23/03
 * @author	Jim Graham
 */
public abstract class Ellipse2D extends RectangularShape {
    /**
     * The <code>Float</code> class defines an ellipse specified 
     * in <code>float</code> precision.
     */
    public static class Float extends Ellipse2D {
	/**
	 * The x coordinate of the upper left corner of this
         * <code>Ellipse2D</code>.
	 */
	public float x;

	/**
	 * The y coordinate of the upper left corner of this
         * <code>Ellipse2D</code>.
	 */
	public float y;

	/**
	 * The overall width of this <code>Ellipse2D</code>.
	 */
	public float width;

	/**
	 * The overall height of this <code>Ellipse2D</code>.
	 */
	public float height;

	/**
	 * Constructs a new <code>Ellipse2D</code>, initialized to
         * location (0,&nbsp;0) and size (0,&nbsp;0).
	 */
	public Float() {
	}

	/**
	 * Constructs and initializes an <code>Ellipse2D</code> from the
         * specified coordinates.
	 * @param x,&nbsp;y the coordinates of the bounding rectangle
	 * @param w the width of the bounding rectangle
	 * @param h the height of the bounding rectangle
	 */
	public Float(float x, float y, float w, float h) {
	    setFrame(x, y, w, h);
	}

	/**
	 * Returns the X coordinate of the upper left corner of this 
         * <code>Ellipse2D</code> in <code>double</code> precision.
         * @return the X coordinate of the upper left corner of the 
         * bounding rectangle of this <code>Ellipse2D</code>.
	 */
	public double getX() {
	    return (double) x;
	}

	/**
	 * Returns the Y coordinate of the upper left corner of this
         * <code>Ellipse2D</code> in <code>double</code> precision.
         * @return the Y coordinate of the upper left corner of the
         * bounding rectangle of this <code>Ellipse2D</code>.
	 */
	public double getY() {
	    return (double) y;
	}

	/**
	 * Returns the overall width of this <code>Ellipse2D</code> in
         * <code>double</code> precision.
         * @return the width of this <code>Ellipse2D</code>.
	 */
	public double getWidth() {
	    return (double) width;
	}

	/**
	 * Returns the overall height of this <code>Ellipse2D</code> in
         * <code>double</code> precision.
         * @return the height of this <code>Ellipse2D</code>.
	 */
	public double getHeight() {
	    return (double) height;
	}

	/**
	 * Determines whether or not the bounding box of this
         * <code>Ellipse2D</code> is empty.
         * @return <code>true</code> if the bounding rectangle of this
         * <code>Ellipse2D</code> is empty; <code>false</code> otherwise.
	 */
	public boolean isEmpty() {
	    return (width <= 0.0 || height <= 0.0);
	}

	/**
	 * Sets the location and size of this <code>Ellipse2D</code> to
         * the specified <code>float</code> values.
         * @param x,&nbsp;y the specified coordinates to which to set
         * the location of the bounding box of this <code>Ellipse2D</code>
         * @param w the specified width to which to set the width of
         * this <code>Ellipse2D</code>
         * @param h the specified height to which to set the height of
         * the <code>Ellipse2D</code>
	 */
	public void setFrame(float x, float y, float w, float h) {
	    this.x = x;
	    this.y = y;
	    this.width = w;
	    this.height = h;
	}

	/**
	 * Sets the location and size of this <code>Ellipse2D</code> to
         * the specified <code>double</code> values.
         * @param x,&nbsp;y the specified coordinates to which to set
         * the location of the bounding box of this <code>Ellipse2D</code>
         * @param w the specified width to which to set the width of
         * this <code>Ellipse2D</code>
         * @param h the specified height to which to set the height of
         * this <code>Ellipse2D</code>
	 */
	public void setFrame(double x, double y, double w, double h) {
	    this.x = (float) x;
	    this.y = (float) y;
	    this.width = (float) w;
	    this.height = (float) h;
	}

	/**
	 * Returns the high precision bounding box of this 
         * <code>Ellipse2D</code>.
         * @return a {@link Rectangle2D} that is the bounding box
         * of this <code>Ellipse2D</code>.
	 */
	public Rectangle2D getBounds2D() {
	    return new Rectangle2D.Float(x, y, width, height);
	}
    }

    /**
     * The <code>Double</code> class defines an ellipse specified
     * in <code>double</code> precision.
     */
    public static class Double extends Ellipse2D {
	/**
	 * The x coordinate of the upper left corner of this
         * <code>Ellipse2D</code>.
	 */
	public double x;

	/**
	 * The y coordinate of the upper left corner of this
         * <code>Ellipse2D</code>.
	 */
	public double y;

	/**
	 * The overall width of this <code>Ellipse2D</code>.
	 */
	public double width;

	/**
	 * The overall height of the <code>Ellipse2D</code>.
	 */
	public double height;

	/**
	 * Constructs a new <code>Ellipse2D</code>, initialized to
         * location (0,&nbsp;0) and size (0,&nbsp;0).
	 */
	public Double() {
	}

	/**
	 * Constructs and initializes an <code>Ellipse2D</code> from the
         * specified coordinates.
	 * @param x,&nbsp;y the coordinates of the bounding rectangle
	 * @param w the width of the rectangle
	 * @param h the height of the rectangle
	 */
	public Double(double x, double y, double w, double h) {
	    setFrame(x, y, w, h);
	}

	/**
	 * Returns the X coordinate of the upper left corner of this
         * <code>Ellipse2D</code> in <code>double</code> precision.
         * @return the X coordinate of the upper left corner of
         * the bounding box of this <code>Ellipse2D</code>.
	 */
	public double getX() {
	    return x;
	}

	/**
	 * Returns the Y coordinate of the upper left corner of this
         * <code>Ellipse2D</code> in <code>double</code> precision.
         * @return the Y coordinate of the upper left corner of
         * the bounding box of this <code>Ellipse2D</code>.
	 */
	public double getY() {
	    return y;
	}

	/**
	 * Returns the overall width of this <code>Ellipse2D</code> 
         * in <code>double</code> precision.
         * @return the width of this <code>Ellipse2D</code>.
	 */
	public double getWidth() {
	    return width;
	}

	/**
	 * Returns the overall height of this <code>Ellipse2D</code> 
         * in <code>double</code> precision.
         * @return the height of this <code>Ellipse2D</code>.
	 */
	public double getHeight() {
	    return height;
	}

	/**
	 * Determines whether or not the bounding box of this 
         * <code>Ellipse2D</code> is empty.
         * @return <code>true</code> if the bounding box of this 
         * <code>Ellipse2D</code> is empty; 
         * <code>false</code> otherwise.
	 */
	public boolean isEmpty() {
	    return (width <= 0.0 || height <= 0.0);
	}

	/**
	 * Sets the location and size of this <code>Ellipse2D</code>
         * to the specified <code>double</code> values.
         * @param x,&nbsp;y the specified coordinates to which to set 
         * the location of the bounding box of this <code>Ellipse2D</code>
         * @param w the width to which to set the width of this 
         * <code>Ellipse2D</code>
         * @param h the height to which to set the height of this 
         * <code>Ellipse2D</code>
	 */
	public void setFrame(double x, double y, double w, double h) {
	    this.x = x;
	    this.y = y;
	    this.width = w;
	    this.height = h;
	}

	/**
	 * Returns the high precision bounding box of this
         * <code>Ellipse2D</code>.
         * @return a <code>Rectangle2D</code> that is the bounding
         * box of this <code>Ellipse2D</code>.
	 */
	public Rectangle2D getBounds2D() {
	    return new Rectangle2D.Double(x, y, width, height);
	}
    }

    /**
     * This is an abstract class that cannot be instantiated directly.
     * Type-specific implementation subclasses are available for
     * instantiation and provide a number of formats for storing
     * the information necessary to satisfy the various accessor
     * methods below.
     *
     * @see java.awt.geom.Ellipse2D.Float
     * @see java.awt.geom.Ellipse2D.Double
     */
    protected Ellipse2D() {
    }

    /**
     * Tests if a specified point is inside the boundary of this 
     * <code>Ellipse2D</code>.
     * @param x,&nbsp;y the coordinates to test
     * @return <code>true</code> if the specified point is contained
     * in this ellipse; <code>false</code> otherwise.
     */
    public boolean contains(double x, double y) {
	// Normalize the coordinates compared to the ellipse
	// having a center at 0,0 and a radius of 0.5.
	double ellw = getWidth();
	if (ellw <= 0.0) {
	    return false;
	}
	double normx = (x - getX()) / ellw - 0.5;
	double ellh = getHeight();
	if (ellh <= 0.0) {
	    return false;
	}
	double normy = (y - getY()) / ellh - 0.5;
	return (normx * normx + normy * normy) < 0.25;
    }

    /**
     * Tests if the interior of this <code>Ellipse2D</code> intersects 
     * the interior of a specified rectangular area.
     * @param x,&nbsp;y the coordinates of the upper left corner of the
     * specified rectangular area
     * @param w the width of the specified rectangular area
     * @param h the height of the specified rectangluar area
     * @return <code>true</code> if this <code>Ellipse2D</code> contains
     * the specified rectangular area; <code>false</code> otherwise.
     */
    public boolean intersects(double x, double y, double w, double h) {
	if (w <= 0.0 || h <= 0.0) {
	    return false;
	}
	// Normalize the rectangular coordinates compared to the ellipse
	// having a center at 0,0 and a radius of 0.5.
	double ellw = getWidth();
	if (ellw <= 0.0) {
	    return false;
	}
	double normx0 = (x - getX()) / ellw - 0.5;
	double normx1 = normx0 + w / ellw;
	double ellh = getHeight();
	if (ellh <= 0.0) {
	    return false;
	}
	double normy0 = (y - getY()) / ellh - 0.5;
	double normy1 = normy0 + h / ellh;
	// find nearest x (left edge, right edge, 0.0)
	// find nearest y (top edge, bottom edge, 0.0)
	// if nearest x,y is inside circle of radius 0.5, then intersects
	double nearx, neary;
	if (normx0 > 0.0) {
	    // center to left of X extents
	    nearx = normx0;
	} else if (normx1 < 0.0) {
	    // center to right of X extents
	    nearx = normx1;
	} else {
	    nearx = 0.0;
	}
	if (normy0 > 0.0) {
	    // center above Y extents
	    neary = normy0;
	} else if (normy1 < 0.0) {
	    // center below Y extents
	    neary = normy1;
	} else {
	    neary = 0.0;
	}
	return (nearx * nearx + neary * neary) < 0.25;
    }

    /**
     * Tests if the interior of this <code>Ellipse2D</code> entirely
     * contains the specified rectangular area.
     * @param x,&nbsp;y the coordinates of the upper left corner of the
     * specified rectangular area
     * @param w the width of the specified rectangular area
     * @param h the height of the specified rectangular area
     * @return <code>true</code> if this <code>Ellipse2D</code> contains
     * the specified rectangular area; <code>false</code> otherwise.
     */
    public boolean contains(double x, double y, double w, double h) {
	return (contains(x, y) &&
		contains(x + w, y) &&
		contains(x, y + h) &&
		contains(x + w, y + h));
    }

    /**
     * Returns an iteration object that defines the boundary of this
     * <code>Ellipse2D</code>.
     * The iterator for this class is multi-threaded safe, which means
     * that this <code>Ellipse2D</code> class guarantees that
     * modifications to the geometry of this <code>Ellipse2D</code> 
     * object do not affect any iterations of that geometry that
     * are already in process.
     * @param at an optional <code>AffineTransform</code> to be applied to
     * the coordinates as they are returned in the iteration, or
     * <code>null</code> if untransformed coordinates are desired
     * @return    the <code>PathIterator</code> object that returns the
     *          geometry of the outline of this <code>Ellipse2D</code>,
     *		one segment at a time.
     */
    public PathIterator getPathIterator(AffineTransform at) {
	return new EllipseIterator(this, at);
    }
}