Java Tutorial/SWT 2D Graphics/SWT Paint

A dynamic gradient

/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
/*
 * Control example snippet: a dynamic gradient
 * 
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 * 
 * @since 3.2
 */
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
public class GradientDynamic {
  static Image oldImage;
  public static void main(String[] args) {
    final Display display = new Display();
    final Shell shell = new Shell(display);
    shell.setBackgroundMode(SWT.INHERIT_DEFAULT);
    shell.addListener(SWT.Resize, new Listener() {
      public void handleEvent(Event event) {
        Rectangle rect = shell.getClientArea();
        Image newImage = new Image(display, Math.max(1, rect.width), 1);
        GC gc = new GC(newImage);
        gc.setForeground(display.getSystemColor(SWT.COLOR_WHITE));
        gc.setBackground(display.getSystemColor(SWT.COLOR_BLUE));
        gc.fillGradientRectangle(rect.x, rect.y, rect.width, 1, false);
        gc.dispose();
        shell.setBackgroundImage(newImage);
        if (oldImage != null){
          oldImage.dispose();
        }
        oldImage = newImage;
      }
    });
    shell.pack();
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    if (oldImage != null)
      oldImage.dispose();
    display.dispose();
  }
}

Alpha blending

/*******************************************************************************
 * Copyright (c) 2000, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
/* 
 * Drawing with transformations, paths and alpha blending
 *
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 * 
 * @since 3.1
 */
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Font;
import org.eclipse.swt.graphics.FontData;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.Path;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
public class FillDrawPath {
  public static void main(String[] args) {
    final Display display = new Display();
    final Shell shell = new Shell(display);
    FontData fd = shell.getFont().getFontData()[0];
    final Font font = new Font(display, fd.getName(), 60, SWT.BOLD | SWT.ITALIC);
    final Image image = new Image(display, 640, 480);
    final Rectangle rect = image.getBounds();
    GC gc = new GC(image);
    gc.setBackground(display.getSystemColor(SWT.COLOR_RED));
    gc.fillOval(rect.x, rect.y, rect.width, rect.height);
    gc.dispose();
    shell.addListener(SWT.Paint, new Listener() {
      public void handleEvent(Event event) {
        GC gc = event.gc;
        gc.drawImage(image, 0, 0, rect.width, rect.height, 0, 0, rect.width / 2, rect.height / 2);
        gc.setAlpha(100);
        Path path = new Path(display);
        path.addString("SWT", 0, 0, font);
        gc.setBackground(display.getSystemColor(SWT.COLOR_GREEN));
        gc.setForeground(display.getSystemColor(SWT.COLOR_BLUE));
        gc.fillPath(path);
        gc.drawPath(path);
        path.dispose();
      }
    });
    shell.setSize(shell.ruputeSize(rect.width / 2, rect.height / 2));
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    image.dispose();
    font.dispose();
    display.dispose();
  }
}

A paint canvas.

/* 
 * JFreeChart : a free chart library for the Java(tm) platform
 * 
 *
 * (C) Copyright 2000-2007, by Object Refinery Limited and Contributors.
 *
 * Project Info:  http://www.jfree.org/jfreechart/index.html
 *
 * This library is free software; you can redistribute it and/or modify it 
 * under the terms of the GNU Lesser General Public License as published by 
 * the Free Software Foundation; either version 2.1 of the License, or 
 * (at your option) any later version.
 *
 * This library 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 Lesser General Public 
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, 
 * USA.  
 *
 * [Java is a trademark or registered trademark of Sun Microsystems, Inc. 
 * in the United States and other countries.]
 *
 * -------------------
 * SwtPaintCanvas.java
 * -------------------
 * (C) Copyright 2000-2007, by Object Refinery Limited.
 *
 * Original Author:  Henry Proudhon (henry.proudhon AT ensmp.fr);
 * Contributor(s):   David Gilbert (for Object Refinery Limited);
 *
 * Changes
 * -------
 * 04-Aug-2006 : New class (HP);
 * 25-Oct-2007 : Fixed Eclipse warnings (DG);
 * 
 */

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.widgets.Canvas;
import org.eclipse.swt.widgets.ruposite;
/**
 * A paint canvas.
 */
public class SWTPaintCanvas extends Canvas {
    private Color myColor;
    
    /**
     * Creates a new instance.
     * 
     * @param parent  the parent.
     * @param style  the style.
     * @param color  the color.
     */
    public SWTPaintCanvas(Composite parent, int style, Color color) {
        this(parent, style);
        setColor(color);
    }
    
    /**
     * Creates a new instance.
     * 
     * @param parent  the parent.
     * @param style  the style.
     */
    public SWTPaintCanvas(Composite parent, int style) {
        super(parent, style);
        addPaintListener(new PaintListener() {
            public void paintControl(PaintEvent e) {
                e.gc.setForeground(e.gc.getDevice().getSystemColor(
                        SWT.COLOR_BLACK));
                e.gc.setBackground(SWTPaintCanvas.this.myColor);
                e.gc.fillRectangle(getClientArea());
                e.gc.drawRectangle(getClientArea().x, getClientArea().y, 
                        getClientArea().width - 1, getClientArea().height - 1);
            }
        });
    }
    
    /**
     * Sets the color.
     * 
     * @param color  the color.
     */
    public void setColor(Color color) {
        if (this.myColor != null) {
            this.myColor.dispose();
        }
        //this.myColor = new Color(getDisplay(), color.getRGB());
        this.myColor = color;
    }
    /**
     * Returns the color.
     * 
     * @return The color.
     */
    public Color getColor() {
        return this.myColor;
    }
    
    /**
     * Overridden to do nothing.
     * 
     * @param c  the color.
     */
    public void setBackground(Color c) {
        return;
    }
    /**
     * Overridden to do nothing.
     * 
     * @param c  the color.
     */
    public void setForeground(Color c) {
        return;
    }
    
    /**
     * Frees resources.
     */
    public void dispose() {
        this.myColor.dispose();
    }
}

Implement a simple scribble program

/*******************************************************************************
 * Copyright (c) 2000, 2004 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Shell;
public class ScribbleProgram {
  public static void main(String[] args) {
    Display display = new Display();
    final Shell shell = new Shell(display);
    Listener listener = new Listener() {
      int lastX = 0, lastY = 0;
      public void handleEvent(Event event) {
        switch (event.type) {
        case SWT.MouseMove:
          if ((event.stateMask & SWT.BUTTON1) == 0)
            break;
          GC gc = new GC(shell);
          gc.drawLine(lastX, lastY, event.x, event.y);
          gc.dispose();
        case SWT.MouseDown:
          lastX = event.x;
          lastY = event.y;
          break;
        }
      }
    };
    shell.addListener(SWT.MouseDown, listener);
    shell.addListener(SWT.MouseMove, listener);
    shell.open();
    while (!shell.isDisposed()) {
      if (!display.readAndDispatch())
        display.sleep();
    }
    display.dispose();
  }
}