使用Java实现签字功能的示例代码

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import com.itextpdf.text.Document;
import com.itextpdf.text.DocumentException;
import com.itextpdf.text.Image;
import com.itextpdf.text.Rectangle;
import com.itextpdf.text.pdf.PdfContentByte;
import com.itextpdf.text.pdf.PdfWriter;
public class SignatureDemo {
    public static void main(String[] args) {
        SignatureFrame frame = new SignatureFrame();
        frame.setVisible(true);
    }
}
class SignatureFrame extends JFrame {
    private static final long serialVersionUID = 1L;
    private JPanel contentPanel;
    public SignatureFrame() {
        setTitle("签字");
        setSize(800, 600);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        contentPanel = new JPanel();
        setContentPane(contentPanel);
        // 添加按钮，用于触发签名事件
        JButton button = new JButton("签字");
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                // 显示签名面板
                SignaturePanel panel = new SignaturePanel();
                int result = JOptionPane.showConfirmDialog(contentPanel, panel, "签字", JOptionPane.OK_CANCEL_OPTION);
                if (result == JOptionPane.OK_OPTION) {
                    // 获取签名图像并保存到本地
                    saveSignatureImage(panel.getSignatureImage());
                }
            }
        });
        contentPanel.add(button);
    }
    /**
     * 保存签名图像到本地
     */
    private void saveSignatureImage(BufferedImage image) {
        // 打开文件选择器
        JFileChooser fileChooser = new JFileChooser();
        int result = fileChooser.showSaveDialog(contentPanel);
        if (result == JFileChooser.APPROVE_OPTION) {
            // 获取用户选择的文件路径
            File file = fileChooser.getSelectedFile();
            // 将图像保存为PNG格式
            try (OutputStream out = new FileOutputStream(file)) {
                ImageIO.write(image, "PNG", out);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
class SignaturePanel extends JPanel {
    private static final long serialVersionUID = 1L;
    private BufferedImage signatureImage;
    public SignaturePanel() {
        setPreferredSize(new Dimension(400, 300));
        setBackground(Color.WHITE);
        setBorder(BorderFactory.createLineBorder(Color.BLACK));
        // 添加鼠标监听器，用于绘制签名
        addMouseListener(new MouseAdapter() {
            @Override
            public void mousePressed(MouseEvent e) {
                // 创建新的图像，用于绘制签名
                signatureImage = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
                Graphics2D g = signatureImage.createGraphics();
                g.setColor(Color.BLACK);
                g.setStroke(new BasicStroke(2));
                g.drawLine(e.getX(), e.getY(), e.getX(), e.getY());
                g.dispose();
                repaint();
            }
        });
        addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                // 绘制签名
                Graphics2D g = signatureImage.createGraphics();
                g.setColor(Color.BLACK);
                g.setStroke(new BasicStroke(2));
                g.drawLine(e.getX(), e.getY(), e.getX(), e.getY());
                g.dispose();
                repaint();
            }
        });
    }
    public BufferedImage getSignatureImage() {
        return signatureImage;
    }
    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        if (signatureImage != null) {
            g.drawImage(signatureImage, 0, 0, null);
        }
    }
}
class PDFUtils {
    /**
     * 在PDF文档中添加签名
     */
    public static void addSignatureToPDF(File pdfFile, BufferedImage signatureImage) throws IOException, DocumentException {
        Rectangle pageSize = new Rectangle(PageSize.A4);
        Document document = new Document(pageSize);
        PdfWriter writer = PdfWriter.getInstance(document, new FileOutputStream(pdfFile.getAbsolutePath() + ".signed.pdf"));
        document.open();
        PdfContentByte canvas = writer.getDirectContent();
        // 将签名图像添加到PDF文档中
        Image image = Image.getInstance(signatureImage, null);
        image.scaleToFit(100, 50);
        float x = (document.right() - image.getScaledWidth()) / 2;
        float y = (document.top() - image.getScaledHeight()) / 2;
        canvas.addImage(image, image.getScaledWidth(), 0, 0, image.getScaledHeight(), x, y);
        document.close();
        writer.close();
    }
}

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception{
        // 创建画布
        Canvas canvas = new Canvas(500, 500);
        GraphicsContext gc = canvas.getGraphicsContext2D();
        // 设置画笔的属性
        gc.setLineWidth(2);
        gc.setStroke(Color.BLACK);
        // 重写鼠标事件的方法
        canvas.setOnMouseDragged(e -> {
            double x = e.getX();
            double y = e.getY();
            gc.lineTo(x, y); // 绘制线条
            gc.stroke(); // 描边
        });
        // 创建主场景
        Scene scene = new Scene(new Group(canvas), 500, 500);
        // 显示窗口
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    public static void main(String[] args) {
        launch(args);
    }
}

public class Main extends JFrame {
    public Main() {
        // 创建面板
        JPanel panel = new JPanel();
        // 设置面板的大小和背景色
        panel.setPreferredSize(new Dimension(500, 500));
        panel.setBackground(Color.WHITE);
        // 重写鼠标事件的方法
        panel.addMouseMotionListener(new MouseMotionAdapter() {
            @Override
            public void mouseDragged(MouseEvent e) {
                Graphics g = panel.getGraphics();
                // 设置画笔的属性
                ((Graphics2D)g).setStroke(new BasicStroke(2));
                g.setColor(Color.BLACK);
                // 绘制线条
                g.drawLine(e.getX(), e.getY(), e.getX(), e.getY());
            }
        });
        // 添加面板到窗口中
        getContentPane().add(panel);
        // 设置窗口的属性
        setTitle("签字功能");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(500, 500);
        setLocationRelativeTo(null);
        setResizable(false);
        setVisible(true);
    }
    public static void main(String[] args) {
        new Main();
    }
}