如何在透明窗口上绘制图像？ [英] How to draw images on transparent window?

问题描述

我正在尝试在JFrame上使用Graphics2D绘制图像。

但是这段代码只显示空白背景。

怎么做？

I'm trying to draw Images with Graphics2D on JFrame.
But this code only displays blank background.
How to do that?

Java版本：SE-1.6

IDE：Eclipse

Java Version: SE-1.6
IDE: Eclipse

我的代码如下所示：

import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Graphics2D;
import java.awt.image.BufferStrategy;
import java.awt.geom.Line2D;
import java.util.TimerTask;

import javax.swing.JFrame;

public class GraphicTest extends JFrame{

    public static void main(String[] args) {
        GraphicTest gt = new GraphicTest();
        gt.start();
    }

    JFrame frame;
    BufferStrategy strategy;

    GraphicTest(){
        int width = 320;
        int height = 240;

        this.frame = new JFrame("test");

        this.frame.setSize(width, height);
        this.frame.setLocationRelativeTo(null);
        this.frame.setLocation(576, 336);
        this.frame.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);

        this.frame.setUndecorated(true);
        this.frame.setBackground(new Color(0, 0, 0, 50));

        this.frame.setVisible(true);

        this.frame.setIgnoreRepaint(true);
        this.frame.createBufferStrategy(2);
        this.strategy = this.frame.getBufferStrategy();
    }

    public void onExit(){
        System.exit(0);
    }

    void start(){
        java.util.Timer timer = new java.util.Timer();
        timer.schedule(new RenderTask(), 0, 16);
    }

    class RenderTask extends TimerTask{
        int count = 0;

        @Override
        public void run() {
            GraphicTest.this.render();
        }
    }

    void render() {
        // Some moving images
        Graphics2D g2 = (Graphics2D)this.strategy.getDrawGraphics();
        g2.setStroke(new BasicStroke(5.0f));
        Line2D line = new Line2D.Double(20, 40, 120, 140);
        g2.draw(line);
        this.strategy.show();
    }
}

感谢您提供任何帮助。

推荐答案

• BufferStrategy 通常与重量相关组件，没有任何透明概念。


• 透明和半透明（每个alpha像素）在Java 6下没有正式支持


• 制作一个半透明的窗口会影响其他任何东西......这非常烦人，无论你使用的是Java 6还是7


• BufferStrategy is normally associated with heavy weight components, which don't have any concept of transparency.
• Transparent and translucent (per alpha pixeling) is not "officially" supported under Java 6
• Making a window translucent effects anything else painted to it...this very annoying, regardless if you are using Java 6 or 7

秘诀是让Window开始透明，然后覆盖一个具有特殊半透明绘画效果的透明组件。

The secret is to make the Window transparent to begin with, then overlay a transparent component that has a special "translucent" paint effect.

在Java 6下（我认为更新10） ），有一个名为 AWTUtilities 的私有API，它提供了使窗口透明或半透明的能力，以下示例基于该API。

Under Java 6 (update 10 I think), there became available a private API called AWTUtilities which provide the ability to make a window transparent or translucent, the following example is based on that API.

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.lang.reflect.Method;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TransparentWindowAnimation {

    public static void main(String[] args) {
        new TransparentWindowAnimation();
    }

    public TransparentWindowAnimation() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                if (supportsPerAlphaPixel()) {
                    try {
                        JFrame frame = new JFrame("Testing");
                        frame.setUndecorated(true);
                        setOpaque(frame, false);
                        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                        frame.setLayout(new BorderLayout());
                        frame.add(new PaintPane());
                        frame.pack();
                        frame.setLocationRelativeTo(null);
                        frame.setVisible(true);
                    } catch (Exception exp) {
                        exp.printStackTrace();
                    }
                } else {
                    System.err.println("Per pixel alphering is not supported");
                }
            }
        });
    }

    public static boolean supportsPerAlphaPixel() {
        boolean support = false;
        try {
            Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities");
            support = true;
        } catch (Exception exp) {
        }
        return support;
    }

    public static void setOpaque(Window window, boolean opaque) throws Exception {
        try {
            Class<?> awtUtilsClass = Class.forName("com.sun.awt.AWTUtilities");
            if (awtUtilsClass != null) {
                Method method = awtUtilsClass.getMethod("setWindowOpaque", Window.class, boolean.class);
                method.invoke(null, window, opaque);
            }
        } catch (Exception exp) {
            throw new Exception("Window opacity not supported");
        }
    }

    public class PaintPane extends JPanel {

        private BufferedImage img;

        private int xPos, yPos = 100;
        private int xDelta = 0;
        private int yDelta = 0;

        public PaintPane() {
            while (xDelta == 0) {
                xDelta = (int)((Math.random() * 8)) - 4;
            }
            while (yDelta == 0) {
                yDelta = (int)((Math.random() * 8)) - 4;
            }
            setOpaque(false);
            try {
                img = ImageIO.read(new File("AngryBird.png"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }

            Timer timer = new Timer(40, new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    xPos += xDelta;
                    yPos += yDelta;
                    if (xPos - (img.getWidth() / 2) <= 0) {
                        xPos = img.getWidth() / 2;
                        xDelta *= -1;
                    }
                    if (xPos + (img.getWidth() / 2) >= getWidth()) {
                        xPos = getWidth() - (img.getWidth() / 2);
                        xDelta *= -1;
                    }
                    if (yPos - (img.getHeight() / 2) <= 0) {
                        yPos = img.getHeight() / 2;
                        yDelta *= -1;
                    }
                    if (yPos + (img.getHeight() / 2) >= getHeight()) {
                        yPos = getHeight() - (img.getHeight() / 2);
                        yDelta *= -1;
                    }
                    repaint();
                }
            });
            timer.start();
        }

        @Override
        public Dimension getPreferredSize() {
            return new Dimension(200, 200);
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Graphics2D g2d = (Graphics2D) g.create();
            g2d.setColor(new Color(128, 128, 128, 128));
            g2d.fillRect(0, 0, getWidth(), getHeight());
            int x = xPos - (img.getWidth() / 2);
            int y = yPos - (img.getHeight()/ 2);
            g2d.drawImage(img, x, y, this);
            g2d.dispose();
        }
    }

}

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