AlphaComposite透明度与重绘重叠为黑色 [英] AlphaComposite Transparency with repaint overlaps into black

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本文介绍了AlphaComposite透明度与重绘重叠为黑色的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

因此，我在另一个面板的顶部有一个图像，并且该图像是透明的，因此您可以看到它下面的面板。我想要做的是使用repaint（）来淡出图像（使用java.awt.Graphics中的drawImage（）方法绘制），直到它完全透明，这样您就可以清楚地看到它下方的面板。到目前为止，图像只是渐变为黑色，而不是透明的纹理。



这是我现在的一些代码：



paintComponent方法： 

  public void paintComponent（Graphics g）
 {
 super.paintComponent（g）; 
 float alpha = 1f  - （。01f *（float）opcounter）; 
 Graphics2D g2d =（Graphics2D）g; 
 g2d.setComposite（AlphaComposite.getInstance（AlphaComposite.SRC_IN，alpha）; 
 g2d.drawImage（img，0，0，null）; 
}

为计时器调用的actionPerformed方法 

  public void actionPerformed（ActionEvent e）
 {
 opcouner ++; 
 panel.repaint（）; 
}
$ b $ p我的代码的更长版本（包括paintComponent和Mover类的定时器）

  public void paintComponent（Graphics g）
 {
 super.paintComponent（g）; 
 Dimension framesize = frame.getSize（）; 
 this.setBounds（ 0,0，framesize.width，framesize.height-61）; 
 
 if（buff）
 {
 //this.add(buffer）; 
 if （opcounter< = 255）
 {
 buffer.set前景（新颜色（250,250,250，0 + opcounter））; 
} 
 else 
 {
 opcounter = 0; 
 buff = false; 
 hand = true; 
 
 
 if（hand）
 {
 this.add（handson）; 
 if（opcounter <= 255）
 {
 handson.setForeground（new Color（250,250,250，0 + opcounter））; 
} 
 else 
 {
 opcounter = 0; 
 hand = false; 
 log = true;如果（log）
 {
 this.add（logic）; 
 
 
 （opcounter< = 255）
 {
 logic.setForeground（new Color（250,250,250，0 + opcounter））; 
 if; 
} 
 else 
 {
 opcounter = 0; 
 log = false; 
 pan = true; （pan）
 {
 this.add（panic）; 
 
 
 
 if（opcounter <= 255）
 {
 panic.setForeground（new Color（250,250,250，0 + opcounter））; 
} 
 else 
 {
 opcounter = 0; 
 pan = false; 
 first = false; 
秒= true; 
尝试
 {
 //Thread.sleep（2000）; 
 
 catch（Exception e）
 {
 System.out.println（thread not sleept）; 
} 
 System.out.println（opcounter =+ opcounter）; 
 black.setVisible（false）; 
 handson.setVisible（false）; 
 logic.setVisible（false）; 
 panic.setVisible（false）; 
 tutpic = true; 
 
 
 if（tutpic）
 {
 if（opcounter< = 200）
 {
 Graphics2D g2d =（Graphics2D） g.create（）; 
 float alpha = 1f  - （。01f *（float）opcounter）; 
 g2d.setComposite（AlphaComposite.getInstance（AlphaComposite.SRC_IN，alpha））; 
 g2d.drawImage（tut，0，0，null）; 
 g2d.dispose（）; 
} 
 else 
 {
 opcounter = 0; 
 tutpic = false; 
 
 
 
 $ b类Mover实现ActionListener 
 {
 public void actionPerformed（ActionEvent e）
 {
 if（！tutpic）
 opcounter + = 4; 
 else 
 {
 opcounter ++; 
} 
 tutorial.repaint（）; 
} 
}

任何帮助将不胜感激。感谢！

解决方案

您需要恢复 Graphics 上下文的状态在存在 paintComponent 方法之前。这是非常重要的，因为图形上下文是一个共享资源，所有需要更新的组件都会被赋予相同的 Graphics ，所以现在你组件后面的每一件事情都会被共享一些 AlphaComposite ...



更好的解决方案是创建 Graphics 上下文的临时副本，应用您想要的任何设置并在完成后处置它。这将确保您在 Graphics 上下文中所做的任何更改不会在该方法存在之后继续进行... 

  public void paintComponent（Graphics g）
 {
 super.paintComponent（g）; 
 float alpha = 1f  - （。01f *（float）opcounter）; 
 //创建您自己的副本... 
 Graphics2D g2d =（Graphics2D）g.create（）; 
 g2d.setComposite（AlphaComposite.getInstance（AlphaComposite.SRC_IN，alpha）; 
 g2d.drawImage（img，0，0，null）; 
 //不要忘记处理它
 g2d.dispose（）; 
}

请记住， 尝试使用 AlphaComposite.SRC_OVER 改为... 




  import java.awt.AlphaComposite; 
 import java.awt.BorderLayout ; 
 import java.awt.Dimension; 
 import java.awt.EventQueue; 
 import java.awt.Graphics; 
 import java.awt.Graphics2D; 
 import java.awt.event.ActionEvent; 
 import java.awt.event.ActionListener; 
 import java.awt.image.BufferedImage; 
 import java.io.File; 
 import java.io.IOException; 
 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 TestFadeOut {
 
 public static void main（String [] args）{
 new TestFadeOut（）; 
 
 $ b public TestFadeOut（）{
 EventQueue.invokeLater（
 new Runnable（）{
 @Override 
 public void run（） {
 try {
 UIManager.setLookAndFeel（UIManager.getSystemLookAndFeelClassName（））; 
} catch（ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex）{
} 
 
 frame.setLayout（new BorderLayout（））; 
 frame.add（new TestPane（Test）; $ b frame.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）; $ b $ frameFrame frame = new JFrame （））; 
 frame.pack（）; 
 frame.setLocationRelativeTo（null）; 
 frame.setVisible（true）; 
} 
}）; 
} 
 
 public class TestPane extends JPanel {
 
 private float alpha = 1f; 
 private float diff = -0.02f; 
 private BufferedImage img; 
 $ b $ public TestPane（）{
 try {
 img = ImageIO.read（new File（C：\\Users\\swhitehead\\Documents \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\'\\\\\ 
 timer timer = new Timer（40，new ActionListener（）{
 @Override 
 public void actionPerformed（ActionEvent e）{
 alpha + = diff; 
 if alpha< 0）{
 diff * = -1; 
 alpha = diff; 
} else if（alpha> 1f）{
 diff * = -1; 
 alpha = 1f + diff; 
} 
 repaint（）; 
} 
}）; 
 timer.setRepeats（true）; 
 timer.setCoalesce（true）; 
 timer.start（）; 
} catch（IOException ex）{
 ex.printStackTrace（）; 
} 
} 
 
 @Override 
 public Dimension getPreferredSize（）{
 return img == null？ super.getPreferredSize（）：new Dimension（img.getWidth（），img.getHeight（））; 
 
 
 @Override 
 protected void paintComponent（Graphics g）{
 super.paintComponent（g）; 
 if（img！= null）{
 Graphics2D g2d =（Graphics2D）g.create（）; 
 g2d.setComposite（AlphaComposite.SrcOver.derive（alpha））; 
 int x = getWidth（） -  img.getWidth（）; 
 int y = getHeight（） -  img.getHeight（）; 
 g2d.drawImage（img，x，y，this）; 
 g2d.dispose（）; 
 
 
 
 
 code 
 $ b $ p $查看堆肥图片了解更多详情... 
 
So I have an image on top of another panel, and that image is transparent so you can see the panel beneath it. What I'm trying to do is use repaint() to fade the image (which is drawn with the drawImage() method in java.awt.Graphics) out until it is completely transparent so you can see the panel beneath it clearly. As of now, the image is just fading into black instead of into a transparent texture.



This is a little bit of my code right now:



paintComponent method:
public void paintComponent(Graphics g)
{
    super.paintComponent(g);
    float alpha = 1f-(.01f*(float)opcounter);
    Graphics2D g2d = (Graphics2D)g;
    g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, alpha);
    g2d.drawImage(img, 0, 0, null);
}

actionPerformed method that is called for the timer 
public void actionPerformed(ActionEvent e)
{
    opcouner++;
    panel.repaint();
}

Longer (uncondensed) version of my code: (including paintComponent and Mover class for timer)
                            public void paintComponent(Graphics g)
            {   
                super.paintComponent(g);
                Dimension framesize = frame.getSize();
                this.setBounds(0,0,framesize.width, framesize.height-61);

                if (buff)
                {
                    //this.add(buffer);
                    if (opcounter <= 255)
                    {
                        buffer.setForeground(new Color(250, 250, 250, 0+opcounter));
                    }
                    else 
                    {
                        opcounter = 0;
                        buff = false;
                        hand = true;
                    }
                }
                if (hand)
                {
                    this.add(handson);
                    if (opcounter <= 255)
                    {
                        handson.setForeground(new Color(250, 250, 250, 0+opcounter));
                    }
                    else 
                    {
                        opcounter = 0;
                        hand = false;
                        log = true;
                    }
                }
                if (log)
                {
                    this.add(logic);
                    if (opcounter <= 255)
                    {
                        logic.setForeground(new Color(250, 250, 250, 0+opcounter));
                    }
                    else 
                    {
                        opcounter = 0;
                        log = false;
                        pan = true;
                    }
                }
                if (pan)
                {
                    this.add(panic);
                    if (opcounter <= 255)
                    {
                        panic.setForeground(new Color(250, 250, 250, 0+opcounter));
                    }
                    else 
                    {
                        opcounter = 0;
                        pan = false;
                        first = false;
                        second = true;
                        try
                        {
                            //Thread.sleep(2000);
                        }
                        catch(Exception e)
                        {
                            System.out.println("thread not slept");
                        }
                        System.out.println("opcounter = " + opcounter);
                        black.setVisible(false);
                        handson.setVisible(false);
                        logic.setVisible(false);
                        panic.setVisible(false);
                        tutpic = true;
                    }
                }
                if (tutpic)
                {
                    if (opcounter <= 200)
                    {
                        Graphics2D g2d = (Graphics2D)g.create();
                        float alpha = 1f-(.01f*(float)opcounter);
                                          g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, alpha));
                        g2d.drawImage(tut, 0, 0, null);
                        g2d.dispose();
                    }
                    else
                    {
                        opcounter = 0;
                        tutpic = false;
                    }
                }
            }

            class Mover implements ActionListener
            {
                public void actionPerformed(ActionEvent e)
                {
                    if (!tutpic)
                        opcounter+=4;
                    else
                    {
                        opcounter++;
                    }
                    tutorial.repaint();
                }   
            }

Any help would be appreciated. Thanks!
 解决方案 
You need to restore the state of the Graphics context BEFORE the paintComponent method exists.  This is very important, as the Graphics context is a shared resource, all the components that need to be updated will be given the same Graphics, so now every thing after you component is painted will share the some AlphaComposite...



A better solution would be to create temporary copy of the Graphics context, apply what ever settings you want to it and dispose of it after you have finished.  This will ensure that what ever changes you make to the Graphics context won't be carried on after the method exists...
public void paintComponent(Graphics g)
{
    super.paintComponent(g);
    float alpha = 1f-(.01f*(float)opcounter);
    // Create your own copy...
    Graphics2D g2d = (Graphics2D)g.create();
    g2d.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, alpha);
    g2d.drawImage(img, 0, 0, null);
    // Don't forget to dispose of it
    g2d.dispose();
}

Remember, you create it, you dispose it!



Update



Try using AlphaComposite.SRC_OVER instead...



import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
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 TestFadeOut {

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

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

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private float alpha = 1f;
        private float diff = -0.02f;
        private BufferedImage img;

        public TestPane() {
            try {
                img = ImageIO.read(new File("C:\\Users\\swhitehead\\Documents\\My Dropbox\\Ponies\\url.png"));
                Timer timer = new Timer(40, new ActionListener() {
                    @Override
                    public void actionPerformed(ActionEvent e) {
                        alpha += diff;
                        if (alpha < 0) {
                            diff *= -1;
                            alpha = diff;
                        } else if (alpha > 1f) {
                            diff *= -1;
                            alpha = 1f + diff;
                        }
                        repaint();
                    }
                });
                timer.setRepeats(true);
                timer.setCoalesce(true);
                timer.start();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return img == null ? super.getPreferredSize() : new Dimension(img.getWidth(), img.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (img != null) {
                Graphics2D g2d = (Graphics2D) g.create();
                g2d.setComposite(AlphaComposite.SrcOver.derive(alpha));
                int x = getWidth() - img.getWidth();
                int y = getHeight() - img.getHeight();
                g2d.drawImage(img, x, y, this);
                g2d.dispose();
            }
        }
    }
}

Have a look at Composting Graphics for more details...


                        
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