java 放大镜效果

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坛里看到, 备忘一下
这里用到第三方库, 主要是做高斯模糊用的,

import com.jhlabs.image.GaussianFilter;
import java.awt.AlphaComposite;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.Point;
import java.awt.Rectangle;
import java.awt.RenderingHints;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionAdapter;
import java.awt.geom.Area;
import java.awt.geom.RoundRectangle2D;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

/**
 *
 * @date 05/02/2013
 */
public class Demo extends JPanel {

    public static void main(String[] args) {

        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {

                JFrame f = new JFrame("Test");
                f.setContentPane(new Demo());
                f.pack();
                f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
                f.setLocationRelativeTo(null);
                f.setVisible(true);
            }
        });
    }
    private BufferedImage image;
    private Image small;
    private Point loc;
    private int halfScaledSize;

    Demo() {

        try {

            image = ImageIO.read(getClass().getResourceAsStream("2.png"));
            small = image.getScaledInstance(image.getWidth() / 2, image.getHeight() / 2, Image.SCALE_SMOOTH);
            halfScaledSize = small.getWidth(this) / 8;
            loc = new Point(0, 0);
        } catch (Exception e) {

            throw new RuntimeException(e);
        }

        setPreferredSize(new Dimension(small.getWidth(this), small.getHeight(this)));

        addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseMoved(MouseEvent e) {

                loc.x = e.getX();
                loc.y = e.getY();
                repaint();
            }
        });
    }

    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);

        g.drawImage(small, 0, 0, this);

        int x = loc.x - halfScaledSize;
        int y = loc.y - halfScaledSize;
        int size = halfScaledSize * 2;

        //绘制阴影
        //BufferedImage shadow = getShadow(Color.BLACK, size + 6, 6);
        //g.drawImage(shadow, x + 3, y + 3, this);

        //抗锯齿
        ((Graphics2D) g).setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        //画白边(大一点的白背景)
        g.setColor(Color.white);
        g.fillRoundRect(x, y, size + 6, size + 6, size + 6, size + 6);

        //画圆角图像
        g.drawImage(getRenderedImage(image, loc.x * 2, loc.y * 2, size),
                x + 3, y + 3, this);
    }

    private BufferedImage getShadow(Color c, int size, int blur) {

        int fix = blur / 2;

        BufferedImage result = new BufferedImage(size, size, BufferedImage.TYPE_INT_ARGB);

        Graphics2D g = result.createGraphics();
        g.setClip(new RoundRectangle2D.Double(fix, fix, size - blur, size - blur, size - blur, size - blur));
        g.setColor(c);
        g.fillRect(0, 0, result.getWidth(), result.getHeight());
        g.dispose();

        //GaussianFilter filter = new GaussianFilter(blur);
        //result = filter.filter(result, result);

        return result;
    }

    private BufferedImage getRenderedImage(
            BufferedImage img, int x, int y, int size) {

        BufferedImage result = new BufferedImage(
                size, size, BufferedImage.TYPE_INT_ARGB);

        Graphics2D g = result.createGraphics();
        g.translate(-x, -y);
        g.drawImage(img, 0, 0, null);
        g.translate(x, y);

        RoundRectangle2D round = new RoundRectangle2D.Double(0, 0, size, size, size, size);
        Area clear = new Area(new Rectangle(0, 0, size, size));
        clear.subtract(new Area(round));
        g.setComposite(AlphaComposite.Clear);
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        g.fill(clear);
        g.dispose();
        return result;
    }
}