/*
 * @(#)GradientPaint.java	1.39 03/12/19
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.awt;

import java.awt.geom.Point2D;
import java.awt.geom.Rectangle2D;
import java.awt.geom.AffineTransform;
import java.awt.image.ColorModel;

/**
 * The <code>GradientPaint</code> class provides a way to fill 
 * a {@link Shape} with a linear color gradient pattern.
 * If {@link Point} P1 with {@link Color} C1 and <code>Point</code> P2 with
 * <code>Color</code> C2 are specified in user space, the
 * <code>Color</code> on the P1, P2 connecting line is proportionally
 * changed from C1 to C2.  Any point P not on the extended P1, P2
 * connecting line has the color of the point P' that is the perpendicular
 * projection of P on the extended P1, P2 connecting line.
 * Points on the extended line outside of the P1, P2 segment can be colored
 * in one of two ways.
 * <ul>
 * <li>
 * If the gradient is cyclic then the points on the extended P1, P2
 * connecting line cycle back and forth between the colors C1 and C2.
 * <li>
 * If the gradient is acyclic then points on the P1 side of the segment
 * have the constant <code>Color</code> C1 while points on the P2 side
 * have the constant <code>Color</code> C2.
 * </ul>
 *
 * @see Paint
 * @see Graphics2D#setPaint
 * @version 10 Feb 1997
 */

public class GradientPaint implements Paint {
    Point2D.Float p1;
    Point2D.Float p2;
    Color color1;
    Color color2;
    boolean cyclic;

    /**
     * Constructs a simple acyclic <code>GradientPaint</code> object.
     * @param x1 x coordinate of the first specified
     * <code>Point</code> in user space
     * @param y1 y coordinate of the first specified
     * <code>Point</code> in user space
     * @param color1 <code>Color</code> at the first specified 
     * <code>Point</code>
     * @param x2 x coordinate of the second specified
     * <code>Point</code> in user space
     * @param y2 y coordinate of the second specified
     * <code>Point</code> in user space
     * @param color2 <code>Color</code> at the second specified 
     * <code>Point</code>
     * @throws NullPointerException if either one of colors is null
     */
    public GradientPaint(float x1,
			 float y1,
			 Color color1,
			 float x2,
			 float y2,
			 Color color2) {
        if ((color1 == null) || (color2 == null)) {
            throw new NullPointerException("Colors cannot be null");
        }

        p1 = new Point2D.Float(x1, y1);
        p2 = new Point2D.Float(x2, y2);
        this.color1 = color1;
        this.color2 = color2;
    }

    /**
     * Constructs a simple acyclic <code>GradientPaint</code> object.
     * @param pt1 the first specified <code>Point</code> in user space
     * @param color1 <code>Color</code> at the first specified 
     * <code>Point</code>
     * @param pt2 the second specified <code>Point</code> in user space
     * @param color2 <code>Color</code> at the second specified 
     * <code>Point</code>
     * @throws NullPointerException if either one of colors or points 
     * is null
     */
    public GradientPaint(Point2D pt1,
			 Color color1,
			 Point2D pt2,
			 Color color2) {
        if ((color1 == null) || (color2 == null) ||
            (pt1 == null) || (pt2 == null)) {
            throw new NullPointerException("Colors and points should be non-null");
        }

        p1 = new Point2D.Float((float)pt1.getX(), (float)pt1.getY());
        p2 = new Point2D.Float((float)pt2.getX(), (float)pt2.getY());
        this.color1 = color1;
        this.color2 = color2;
    }

    /**
     * Constructs either a cyclic or acyclic <code>GradientPaint</code>
     * object depending on the <code>boolean</code> parameter.
     * @param x1 x coordinate of the first specified
     * <code>Point</code> in user space
     * @param y1 y coordinate of the first specified
     * <code>Point</code> in user space
     * @param color1 <code>Color</code> at the first specified 
     * <code>Point</code>
     * @param x2 x coordinate of the second specified
     * <code>Point</code> in user space
     * @param y2 y coordinate of the second specified
     * <code>Point</code> in user space
     * @param color2 <code>Color</code> at the second specified 
     * <code>Point</code>
     * @param cyclic <code>true</code> if the gradient pattern should cycle
     * repeatedly between the two colors; <code>false</code> otherwise
     */
    public GradientPaint(float x1,
			 float y1,
			 Color color1,
			 float x2,
			 float y2,
			 Color color2,
			 boolean cyclic) {
	this (x1, y1, color1, x2, y2, color2);
	this.cyclic = cyclic;
    }

    /**
     * Constructs either a cyclic or acyclic <code>GradientPaint</code>
     * object depending on the <code>boolean</code> parameter.
     * @param pt1 the first specified <code>Point</code> 
     * in user space
     * @param color1 <code>Color</code> at the first specified 
     * <code>Point</code>
     * @param pt2 the second specified <code>Point</code> 
     * in user space
     * @param color2 <code>Color</code> at the second specified 
     * <code>Point</code>
     * @param cyclic <code>true</code> if the gradient pattern should cycle
     * repeatedly between the two colors; <code>false</code> otherwise
     * @throws NullPointerException if either one of colors or points 
     * is null
     */
    public GradientPaint(Point2D pt1,
			 Color color1,
			 Point2D pt2,
			 Color color2,
			 boolean cyclic) {
	this (pt1, color1, pt2, color2);
	this.cyclic = cyclic;
    }

    /**
     * Returns a copy of the point P1 that anchors the first color.
     * @return a {@link Point2D} object that is a copy of the point
     * that anchors the first color of this 
     * <code>GradientPaint</code>.  
     */
    public Point2D getPoint1() {
	return new Point2D.Float(p1.x, p1.y);
    }

    /**
     * Returns the color C1 anchored by the point P1.
     * @return a <code>Color</code> object that is the color
     * anchored by P1.
     */
    public Color getColor1() {
	return color1;
    }

    /**
     * Returns a copy of the point P2 which anchors the second color.
     * @return a {@link Point2D} object that is a copy of the point
     * that anchors the second color of this
     * <code>GradientPaint</code>.
     */
    public Point2D getPoint2() {
	return new Point2D.Float(p2.x, p2.y);
    }

    /**
     * Returns the color C2 anchored by the point P2.
     * @return a <code>Color</code> object that is the color
     * anchored by P2.
     */
    public Color getColor2() {
	return color2;
    }

    /**
     * Returns <code>true</code> if the gradient cycles repeatedly
     * between the two colors C1 and C2.
     * @return <code>true</code> if the gradient cycles repeatedly
     * between the two colors; <code>false</code> otherwise.
     */
    public boolean isCyclic() {
	return cyclic;
    }

    /**
     * Creates and returns a context used to generate the color pattern.
     * @param cm {@link ColorModel} that receives
     * the <code>Paint</code> data. This is used only as a hint.
     * @param deviceBounds the device space bounding box of the 
     * graphics primitive being rendered
     * @param userBounds the user space bounding box of the 
     * graphics primitive being rendered
     * @param xform the {@link AffineTransform} from user
     *     space into device space
     * @param hints the hints that the context object uses to choose
     * between rendering alternatives
     * @return the {@link PaintContext} that generates color patterns.
     * @see PaintContext
     */
    public PaintContext createContext(ColorModel cm,
				      Rectangle deviceBounds,
				      Rectangle2D userBounds,
				      AffineTransform xform,
                                      RenderingHints hints) {

        return new GradientPaintContext(cm, p1, p2, xform,
					color1, color2, cyclic);
    }

    /**
     * Returns the transparency mode for this <code>GradientPaint</code>.
     * @return an integer value representing this <code>GradientPaint</code>
     * object's transparency mode.
     * @see Transparency
     */
    public int getTransparency() {
	int a1 = color1.getAlpha();
	int a2 = color2.getAlpha();
	return (((a1 & a2) == 0xff) ? OPAQUE : TRANSLUCENT);
    }

}