Java example source code file (GradientPaint.java)

This example Java source code file (GradientPaint.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

affinetransform, awt, bean, color, colors, constructorproperties, geometry, gradientpaint, gradientpaintcontext, image, javabean, nullpointerexception, opaque, paintcontext, point2d, rectangle, rectangle2d, renderinghints, translucent

The GradientPaint.java Java example source code

/*
 * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.awt;

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

/**
 * The <code>GradientPaint 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 P2 with
 * <code>Color C2 are specified in user space, the
 * <code>Color 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 C1 while points on the P2 side
 * have the constant <code>Color 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 object.
     * @param x1 x coordinate of the first specified
     * <code>Point in user space
     * @param y1 y coordinate of the first specified
     * <code>Point in user space
     * @param color1 <code>Color at the first specified
     * <code>Point
     * @param x2 x coordinate of the second specified
     * <code>Point in user space
     * @param y2 y coordinate of the second specified
     * <code>Point in user space
     * @param color2 <code>Color at the second specified
     * <code>Point
     * @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 object.
     * @param pt1 the first specified <code>Point in user space
     * @param color1 <code>Color at the first specified
     * <code>Point
     * @param pt2 the second specified <code>Point in user space
     * @param color2 <code>Color at the second specified
     * <code>Point
     * @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
     * object depending on the <code>boolean parameter.
     * @param x1 x coordinate of the first specified
     * <code>Point in user space
     * @param y1 y coordinate of the first specified
     * <code>Point in user space
     * @param color1 <code>Color at the first specified
     * <code>Point
     * @param x2 x coordinate of the second specified
     * <code>Point in user space
     * @param y2 y coordinate of the second specified
     * <code>Point in user space
     * @param color2 <code>Color at the second specified
     * <code>Point
     * @param cyclic <code>true if the gradient pattern should cycle
     * repeatedly between the two colors; <code>false 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
     * object depending on the <code>boolean parameter.
     * @param pt1 the first specified <code>Point
     * in user space
     * @param color1 <code>Color at the first specified
     * <code>Point
     * @param pt2 the second specified <code>Point
     * in user space
     * @param color2 <code>Color at the second specified
     * <code>Point
     * @param cyclic <code>true if the gradient pattern should cycle
     * repeatedly between the two colors; <code>false otherwise
     * @throws NullPointerException if either one of colors or points
     * is null
     */
    @ConstructorProperties({ "point1", "color1", "point2", "color2", "cyclic" })
    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.
     */
    public Point2D getPoint1() {
        return new Point2D.Float(p1.x, p1.y);
    }

    /**
     * Returns the color C1 anchored by the point P1.
     * @return a <code>Color 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.
     */
    public Point2D getPoint2() {
        return new Point2D.Float(p2.x, p2.y);
    }

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

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

    /**
     * Creates and returns a {@link PaintContext} used to
     * generate a linear color gradient pattern.
     * See the {@link Paint#createContext specification} of the
     * method in the {@link Paint} interface for information
     * on null parameter handling.
     *
     * @param cm the preferred {@link ColorModel} which represents the most convenient
     *           format for the caller to receive the pixel data, or {@code null}
     *           if there is no preference.
     * @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 set of hints that the context object can use to
     *              choose between rendering alternatives.
     * @return the {@code PaintContext} for
     *         generating color patterns.
     * @see Paint
     * @see PaintContext
     * @see ColorModel
     * @see Rectangle
     * @see Rectangle2D
     * @see AffineTransform
     * @see RenderingHints
     */
    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.
     * @return an integer value representing this <code>GradientPaint
     * object's transparency mode.
     * @see Transparency
     */
    public int getTransparency() {
        int a1 = color1.getAlpha();
        int a2 = color2.getAlpha();
        return (((a1 & a2) == 0xff) ? OPAQUE : TRANSLUCENT);
    }

}