java pdf 给每页加不同水印 java如何给pdf加水印

给pdf文档加水印！

public static void waterMark(String inputFile,
String outputFile, String waterMarkName) {
try {
PdfReader reader = new PdfReader(inputFile);
PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(
outputFile));
BaseFont base = BaseFont.createFont("STSong-Light", "UniGB-UCS2-H", BaseFont.EMBEDDED);
Rectangle pageRect = null;
PdfGState gs = new PdfGState();
gs.setFillOpacity(0.3f);
gs.setStrokeOpacity(0.4f);
int total = reader.getNumberOfPages() + 1;
JLabel label = new JLabel();
FontMetrics metrics;
int textH = 0;
int textW = 0;
label.setText(waterMarkName);
metrics = label.getFontMetrics(label.getFont());
textH = metrics.getHeight();
textW = metrics.stringWidth(label.getText());
PdfContentByte under;
for (int i = 1; i < total; i++) {
under = stamper.getOverContent(i);// 在内容上方加水印
//content = stamper.getUnderContent(i);//在内容下方加水印
gs.setFillOpacity(0.2f);
// content.setGState(gs);
under.beginText();
under.setFontAndSize(base, 50);
under.setTextMatrix(70, 200);
under.showTextAligned(Element.ALIGN_CENTER, "测试水印！", 300,350, 55);
under.endText();
}
//一定不要忘记关闭流
stamper.close();
reader.close();
} catch (Exception e) {
e.printStackTrace();
}
}