Question

我正在尝试编写一个使用图层的绘图应用程序。我目前有4层，底层是白色，其他都是透明的。同时我只有第3（顶部）图层绘制到缓冲图像，其他由于某种原因只显示预览但不提交图像。即使我实现了图层的透明度，它也不会产生影响。所有层都是黑色的。好的部分是始终显示最顶层。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);

}

    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);

}

public void setListeners(DrawListenerInterface listener) {

    if (listenerInterface != null) {
        this.removeMouseListener(listenerInterface);
        this.removeMouseMotionListener(listenerInterface);

    }
    this.listenerInterface = listener;
    this.addMouseMotionListener(listenerInterface);
    this.addMouseListener(listenerInterface);
}

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    // defaultSettings((Graphics2D) g);

    final Iterator<BufferedImage> iter = images.iterator();
    while (iter.hasNext()) {

        // g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
        g.drawImage(iter.next(), 0, 0, null);
        this.repaint();

    }
    listenerInterface.preview((Graphics2D) g);
    this.repaint();
    // g2.drawImage(images.get(activeLayer), 0, 0, null);

    // }
    // g2.setColor(color);

}

public BufferedImage getImage() {
    return images.get(activeLayer);
}

public int getActiveLayer() {
    return activeLayer;
}

public void setActiveLayer(int activeLayer) {
    this.activeLayer = activeLayer;
}

public void setLayers(int layerNumber) {
    // System.out.println(layer);
    if (layerNumber == 0) {
        final Graphics2D g = (Graphics2D) images.get(0).getGraphics();
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, 800, 600);
    } else {
        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));

    }

    repaint();
}

@Override
public void mouseWheelMoved(MouseWheelEvent arg0) {
    // TODO Auto-generated method stub

}

    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);

Answer 1

您对super.paintComponent(g) Canvas的来电间接致电ComponentUI.update(..)：

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);
}

因此，除非您在某个时刻在组件上调用setOpaque(false)，否则您始终使用背景颜色填充g。

我尝试将不透明设置为false或删除super.paintComponent(g)来电。

代码似乎还有其他问题。您在Canvas构造函数中创建的图片均为TYPE_INT_RGB，即他们不支持 Alpha通道/透明度。但是稍后在setLayers()中对于0以外的图层，您将检索图像img，然后使用新的，支持透明度的图像覆盖它，您从不存储在任何地方：

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

离开相应的区块后，

img就会丢失。

Answer 2

很难理解你的实际问题，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));

即使您为其创建了新实例，也不会将img存储在任何位置。此外，从images获取它，然后在将其设置为其他内容之后立即没有任何意义。

图层透明度不适用于java

2 个答案: