图层透明度在java中不起作用

我正在尝试编写一个使用图层的绘画应用程序。我目前有4层，底部一层是白色，其他所有层都是透明的。同时，我只有第三层（顶部）绘制到缓冲图像，其他人出于某种原因只显示预览，但不提交到图像。而且，即使我实现了层的透明度，它也不会生效。所有的图层都是黑色的。好的方面是，它始终显示最顶层。请帮忙

    public class Canvas extends JComponent implements MouseWheelListener {

private static final long serialVersionUID = 1L;

private final List<BufferedImage> images;
private DrawListenerInterface listenerInterface;
private int activeLayer;
private final Color color;

private final Paint frame;

public Canvas(Paint frame) {
    this.frame = frame;
    this.images = new ArrayList<BufferedImage>();
    this.activeLayer = 0;
    this.color = Color.red;
    for (int i = 0; i < 4; i++) {
        images.add(new BufferedImage(800, 600, BufferedImage.TYPE_INT_RGB));

        setLayers(i);
    }

    this.addMouseWheelListener(this);

}

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在

Canvas

中调用

super.paintComponent（g）

间接调用

ComponentUI.update（…）

：

因此，除非您在某个时候对组件调用

setOpaque（false）

，否则您总是使用背景色填充

g

我会尝试将不透明设置为

false

或删除

super.paintComponent（g）

调用

代码似乎还有其他问题。 您在

画布

构造函数中创建的图像都是

类型_INT_RGB

，即它们不支持alpha通道/透明度。 但随后在

setLayers（）

中，对于0以外的层，您检索图像

img

，然后用一个新的支持透明度的图像覆盖它，该图像从未存储在任何地方：

---

img

在您离开相应的区块后立即丢失。

很难理解您的实际要求，但是：

BufferedImage img = images.get(layerNumber);
img = new BufferedImage(800, 600, BufferedImage.TYPE_INT_ARGB);
final Graphics2D graphics = (Graphics2D) img.getGraphics();
graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.CLEAR));
graphics.fillRect(0, 0, 800, 600);
// reset composite
graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));

---

您没有将

img

存储在任何地方，即使您为它创建了一个新实例。同样，从

图像中获取它，然后在设置为其他内容之后立即获取它也没有意义。
您的回答没有直接帮助我，但是我的整个问题是使用类型为_INT_RGB的BuffereImage，一个类型为_INT_ARGB_的图像在开始工作之前被更改。所以你应该得到一个大+1
    public class DrawListener implements DrawListenerInterface {

private final Canvas canvas;
private int x, y;
private int x2;
private int y2;
private final Paint frame;

public DrawListener(Canvas canvas, Paint frame) {
    this.canvas = canvas;
    this.frame = frame;
}

@Override
public void mouseMoved(MouseEvent e) {

}

@Override
public void mouseDragged(MouseEvent e) {
    // TODO Auto-generated method stub
    this.x2 = e.getX();
    this.y2 = e.getY();
    final Graphics2D g2 = (Graphics2D) canvas.getImage().getGraphics();
    draw(g2);
    canvas.repaint();
    x = x2;
    y = y2;
}

@Override
public void draw(Graphics2D g2) {
    // TODO Auto-generated method stub

    g2.drawLine(x, y, x2, y2);

}

@Override
public void mouseClicked(MouseEvent arg0) {
    // TODO Auto-generated method stub

}

@Override
public void mouseEntered(MouseEvent arg0) {
    // TODO Auto-generated method stub

}

@Override
public void mouseExited(MouseEvent arg0) {
    // TODO Auto-generated method stub

}

@Override
public void mousePressed(MouseEvent e) {
    // TODO Auto-generated method stub
    x = e.getX();
    x2 = e.getX();
    y = e.getY();
    y2 = e.getY();
    final Graphics2D g2 = (Graphics2D) canvas.getImage().getGraphics();
    draw(g2);
    canvas.repaint();
}

@Override
public void mouseReleased(MouseEvent e) {
    // TODO Auto-generated method stub

}

@Override
public void preview(Graphics2D g2) {
    // TODO Auto-generated method stub

}

 public class LayerPanel extends JPanel {

private final JButton layer0, layer1, layer2, layer3;
private final Canvas canvas;

public LayerPanel(Canvas canvas, Paint paint) {
    this.canvas = canvas;

    this.setSize(new Dimension(200, 400));
    this.layer0 = new JButton("Layer 0");
    this.layer1 = new JButton("Layer 1");
    this.layer2 = new JButton("Layer 2");
    this.layer3 = new JButton("Layer 3");

    this.layer0.addActionListener(new ButtonListener());
    this.layer1.addActionListener(new ButtonListener());
    this.layer2.addActionListener(new ButtonListener());
    this.layer3.addActionListener(new ButtonListener());

    this.setLayout(new GridLayout(4, 1));

    this.add(layer3);
    this.add(layer2);
    this.add(layer1);
    this.add(layer0);

}

private class ButtonListener implements ActionListener {

    @Override
    public void actionPerformed(ActionEvent e) {
        // TODO Auto-generated method stub
        layer0.setBackground(Color.gray);
        layer1.setBackground(Color.gray);
        layer2.setBackground(Color.gray);
        layer3.setBackground(Color.gray);
        if (e.getSource().equals(layer0)) {
            canvas.setActiveLayer(0);
            final JButton b = (JButton) e.getSource();
            b.setBackground(Color.yellow);
        } else if (e.getSource().equals(layer1)) {
            canvas.setActiveLayer(1);
            final JButton b = (JButton) e.getSource();
            b.setBackground(Color.yellow);
        } else if (e.getSource().equals(layer2)) {
            canvas.setActiveLayer(2);
            final JButton b = (JButton) e.getSource();
            b.setBackground(Color.yellow);
        } else if (e.getSource().equals(layer3)) {
            canvas.setActiveLayer(3);
            final JButton b = (JButton) e.getSource();
            b.setBackground(Color.yellow);
        }

    }

}

public interface DrawListenerInterface extends MouseListener, MouseMotionListener {

public void draw(Graphics2D g2);

public void preview(Graphics2D g2);

public void update(Graphics g, JComponent c) {
    if (c.isOpaque()) {
        g.setColor(c.getBackground());
        g.fillRect(0, 0, c.getWidth(),c.getHeight());
    }
    paint(g, c);
}

BufferedImage img = images.get(layerNumber);
img = new BufferedImage(800, 600, BufferedImage.TYPE_INT_ARGB);

BufferedImage img = images.get(layerNumber);
img = new BufferedImage(800, 600, BufferedImage.TYPE_INT_ARGB);
final Graphics2D graphics = (Graphics2D) img.getGraphics();
graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.CLEAR));
graphics.fillRect(0, 0, 800, 600);
// reset composite
graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));