java怎么在表格中添加水印

import com.spire.xls.*;
 
import <span><a href="http://www.lanqibing.com/tag/java/" title="View all posts in java" target="_blank">java</a></span>.awt.*;
import <span><a href="http://www.lanqibing.com/tag/java/" title="View all posts in java" target="_blank">java</a></span>.awt.image.BufferedImage;
 
import static <span><a href="http://www.lanqibing.com/tag/java/" title="View all posts in java" target="_blank">java</a></span>.awt.image.BufferedImage.TYPE_INT_ARGB;
 
public class SingleWatermark {
    public static void main(String[] args) {
        //加载Excel测试文档
        Workbook wb = new Workbook();
        wb.loadFromFile("test.xlsx");
 
        //设置文本和字体大小
        Font font = new Font("仿宋", Font.PLAIN, 40);
 
        for (int i =0;i<wb.getWorksheets().getCount();i++)
        {
            Worksheet sheet = wb.getWorksheets().get(i);
            //调用DrawText() 方法插入图片
            BufferedImage imgWtrmrk = drawText("内部专用", font, Color.pink, Color.white, sheet.getPageSetup().getPageHeight(), sheet.getPageSetup().getPageWidth());
 
            //将图片设置为页眉
            sheet.getPageSetup().setCenterHeaderImage(imgWtrmrk);
            sheet.getPageSetup().setCenterHeader("&G");
 
 
            //将显示模式设置为Layout
            sheet.setViewMode(ViewMode.Layout);
        }
 
        //保存文档
        wb.saveToFile("SingleWatermark.xlsx", ExcelVersion.Version2013);
    }
    private static BufferedImage drawText (String text, Font font, Color textColor, Color backColor,double height, double width)
    {
        //定义图片宽度和高度
        BufferedImage img = new BufferedImage((int) width, (int) height, TYPE_INT_ARGB);
 
        Graphics2D loGraphic = img.createGraphics();
 
        //获取文本size
        FontMetrics loFontMetrics = loGraphic.getFontMetrics(font);
        int liStrWidth = loFontMetrics.stringWidth(text);
        int liStrHeight = loFontMetrics.getHeight();
 
        //文本显示样式及位置
        loGraphic.setColor(backColor);
        loGraphic.fillRect(0, 0, (int) width, (int) height);
        loGraphic.translate(((int) width - liStrWidth) / 2, ((int) height - liStrHeight) / 2);
        loGraphic.rotate(Math.toRadians(-45));
 
        loGraphic.translate(-((int) width - liStrWidth) / 2, -((int) height - liStrHeight) / 2);
        loGraphic.setFont(font);
        loGraphic.setColor(textColor);
        loGraphic.drawString(text, ((int) width - liStrWidth) / 2, ((int) height - liStrHeight) / 2);
        loGraphic.dispose();
        return img;
    }
}