Question

我想为Undecorated jFrame添加阴影。我不知道该怎么做。有人知道吗？

Answer 1

这有点“欺骗”。这不会在窗口后面留下阴影，只会在内容后面留下阴影。

这种方法不仅使窗户不整齐，而且透明。替换“内容窗格”部分填充，允许阴影效果“出现”在它后面。

Shadow shadow

import com.jhlabs.image.GaussianFilter;
import java.awt.AlphaComposite;
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.GraphicsConfiguration;
import java.awt.GraphicsEnvironment;
import java.awt.Image;
import java.awt.Insets;
import java.awt.RenderingHints;
import java.awt.Transparency;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.EmptyBorder;

public class TestImageDropShadow {

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

    public TestImageDropShadow() {
        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.setUndecorated(true);
                frame.setBackground(new Color(0, 0, 0, 0));
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setContentPane(new ShadowPane());
                frame.setLayout(new BorderLayout());
                frame.add(new JLabel(new ImageIcon("/you/own/pony")));
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class ShadowPane extends JPanel {

        private BufferedImage shadow;

        public ShadowPane() {
            setOpaque(false);
            setBorder(new EmptyBorder(10, 10, 10, 10));
        }

        @Override
        public void invalidate() {
            shadow = null;
            super.invalidate();
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            Insets insets = getInsets();
            int x = insets.left;
            int y = insets.top;
            int width = getWidth() - (insets.left + insets.right);
            int height = getHeight() - (insets.top + insets.bottom);
            if (shadow == null) {
                // Try and "guess" the amount of shadow we can show...
                int shadowWidth = Math.min(Math.min(insets.left, insets.top), Math.min(insets.right, insets.bottom));
                shadow = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
                Graphics2D g2d = shadow.createGraphics();
                g2d.setColor(getBackground());
                g2d.fillRect(0, 0, width, height);
                g2d.dispose();
                shadow = generateShadow(shadow, shadowWidth, Color.BLACK, 0.5f);
            }
            System.out.println(insets);
            g.drawImage(shadow, 0, 0, this);
            g.setColor(getBackground());
            g.fillRect(x, y, width, height);
        }

    }

    public static void applyQualityRenderingHints(Graphics2D g2d) {
        g2d.setRenderingHint(RenderingHints.KEY_ALPHA_INTERPOLATION, RenderingHints.VALUE_ALPHA_INTERPOLATION_QUALITY);
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
        g2d.setRenderingHint(RenderingHints.KEY_DITHERING, RenderingHints.VALUE_DITHER_ENABLE);
        g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
        g2d.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);
        g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
        g2d.setRenderingHint(RenderingHints.KEY_STROKE_CONTROL, RenderingHints.VALUE_STROKE_PURE);
    }

    public static BufferedImage createCompatibleImage(int width, int height) {
        return createCompatibleImage(width, height, Transparency.TRANSLUCENT);
    }

    public static BufferedImage createCompatibleImage(int width, int height, int transparency) {
        BufferedImage image = getGraphicsConfiguration().createCompatibleImage(width, height, transparency);
        image.coerceData(true);
        return image;
    }

    public static BufferedImage createCompatibleImage(BufferedImage image) {
        return createCompatibleImage(image, image.getWidth(), image.getHeight());
    }

    public static BufferedImage createCompatibleImage(BufferedImage image,
                    int width, int height) {
        return getGraphicsConfiguration().createCompatibleImage(width, height, image.getTransparency());
    }

    public static GraphicsConfiguration getGraphicsConfiguration() {
        return GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
    }

    public static BufferedImage generateBlur(BufferedImage imgSource, int size, Color color, float alpha) {
        GaussianFilter filter = new GaussianFilter(size);

        int imgWidth = imgSource.getWidth();
        int imgHeight = imgSource.getHeight();

        BufferedImage imgBlur = createCompatibleImage(imgWidth, imgHeight);
        Graphics2D g2 = imgBlur.createGraphics();
        applyQualityRenderingHints(g2);

        g2.drawImage(imgSource, 0, 0, null);
        g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_IN, alpha));
        g2.setColor(color);

        g2.fillRect(0, 0, imgSource.getWidth(), imgSource.getHeight());
        g2.dispose();

        imgBlur = filter.filter(imgBlur, null);

        return imgBlur;
    }

    public static BufferedImage generateShadow(BufferedImage imgSource, int size, Color color, float alpha) {
        int imgWidth = imgSource.getWidth() + (size * 2);
        int imgHeight = imgSource.getHeight() + (size * 2);

        BufferedImage imgMask = createCompatibleImage(imgWidth, imgHeight);
        Graphics2D g2 = imgMask.createGraphics();
        applyQualityRenderingHints(g2);

        int x = Math.round((imgWidth - imgSource.getWidth()) / 2f);
        int y = Math.round((imgHeight - imgSource.getHeight()) / 2f);
        g2.drawImage(imgSource, x, y, null);
        g2.dispose();

        // ---- Blur here ---
        BufferedImage imgGlow = generateBlur(imgMask, (size * 2), color, alpha);

        return imgGlow;
    }
}

基本上这里发生的事情是，我们首先让widnow透明化。接下来，我们将内容窗格替换为我们自己的特殊ShadowPane。

此面板是透明的，并且已应用EmptyBorder。这可确保添加到其中的任何内容都适合我们想要的区域。

接下来，我们生成一个BufferedImage来表示组件的整个可用空间，但我们只填充“可查看”区域。我们对此应用阴影并将其绘制到组件中。

此示例使用JHLabs

中的GaussianFilter

严格地说，你不需要它，但它确实提供了一个很好的“模糊”效果

有关更复杂的事情的示例，您可以查看Java: create shadow effect on image

如何在Netbeans中为Undecorated JFrame添加阴影

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